Top Banner
174

Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Mar 25, 2020

Download

Documents

dariahiddleston
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades
Page 2: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

MicrogravityA Teacher’s Guide With Activities

in Science, Mathematics, and Technology

National Aeronautics and Space Administration

Office of Life and Microgravity Sciences and ApplicationsMicrogravity Research Division

Office of Human Resources and EducationEducation Division

This publication is in the Public Domain and is not protected by copyright.Permission is not required for duplication.

EG-1997-08-110-HQ

Page 3: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Acknowledgements This publication was developed for the NationalAeronautics and Space Administration with theassistance of the many educators of theAerospace Education Services Program,Oklahoma State University.

Writers:

Melissa J. B. Rogers, MSTAL-CUT CompanyNASA Lewis Research CenterCleveland, OH

Gregory L. Vogt, Ed-D.Teaching From Space ProgramNASA Johnson Space CenterHouston, TX

Michael J. Wargo, Sc.D.Microgravity Research DivisionNASA HeadquartersWashington, DC

Page 4: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Activity Contributors

Microgravity In The ClassroomAccelerometersAround The WorldInertial BalanceCandle DropCrystallization ModelGregory L. Vogt, Ed.D.Teaching From Space ProgramNASA Johnson Space Center

Gravity-Driven Fluid FlowCharles E. Bugg, Ph.D. Professor EmeritusUniversity of Alabama, BirminghamandChairman and Chief Executive OfficerBiocrypt Pharmaceuticals, Inc.

Craig D. Smith, Ph.D.ManagerX-Ray Crystallography LaboratoryCenter for MacromolecularCrystallographyUniversity of Alabama at Birmingham

Surface Tension-Driven FlowsGregory L. Vogt, Ed.D.Teaching From Space ProgramNASA Johnson Space Center

R. Glynn Holt, Ph.D.Research Assistant ProfessorBoston UniversityAeronautics and Mechanical EngineeringDepartment

Temperature Effects on SurfaceTensionMichael F. SchatzSchool of PhysicsGeorgia Institute of Technology

Stephen J. VanHookCenter for Nonlinear DynamicsDepartment of PhysicsUniversity of Texas at Austin

Candle FlamesHoward D. Ross, Ph.D.ChiefMicrogravity Combustion BranchNASA Lewis Research Center

Crystal Growth and Buoyancy-DrivenConvection CurrentsRoger L. Kroes, Ph.D.ResearcherMicrogravity Science DivisionNASA Marshall Space Flight Center

Donald A. Reiss, Ph.D.ResearcherMicrogravity Science DivisionNASA Marshall Space Flight Center

Rapid CrystallizationMicroscopic Observation of CrystalsDavid Mathiesen, Ph.D.Assistant ProfessorCase Western Reserve UniversityandAlternate Payload SpecialistUSML-2 Mission

Zeolite Crystal GrowthAlbert Sacco, Jr.HeadDepartment of Chemical EngineeringWorchester Polytechnical InstituteandPayload SpecialistUSML-2 Mission

Page 5: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏) i

As opportunities for extended space flight havebecome available, microgravity research inphysical and biological sciences has grown inimportance. Using the Space Shuttle and soon theInternational Space Station, scientists are able toadd long term control of gravity’s effects to theshort list of variables they are to manipulate intheir experiments. Although most people areaware of the floating effects of astronauts andthings in orbiting spacecraft, few understand whatcauses microgravity much less how it can beutilized for research.

The purpose of this curriculum supplement guideis to define and explain microgravity and showhow microgravity can help us learn about thephenomena of our world. The front section of theguide is designed to provide teachers of science,mathematics, and technology at many levels witha foundation in microgravity science andapplications. It begins with backgroundinformation for the teacher on what microgravityis and how it is created. This is followed withinformation on the domains of microgravityscience research; biotechnology, combustionscience, fluid physics, fundamental physics,materials science, and microgravity researchgeared toward exploration. The backgroundsection concludes with a history of microgravityresearch and the expectations microgravityscientists have for research on the InternationalSpace Station.

Following the background information areclassroom activities that enable students toexperiment with the forces and processesmicrogravity scientists are investigating today.The activities employ simple and inexpensivematerials and apparatus that are widely availablein schools. The activities emphasize hands-oninvolvement, prediction, data collection andinterpretation, teamwork, and problem solving.Activity features include objectives, materials andtools lists, management suggestions, assessmentideas, extensions, instructions and illustrations,student work sheets, and student readers.Because many of the activities anddemonstrations apply to more than one subjectarea, a matrix chart relates activities to nationalstandards in science and mathematics and toscience process skills.

Finally, the guide concludes with a suggestedreading list, NASA educational resourcesincluding electronic resources, and an evaluationquestionnaire. We would appreciate yourassistance in improving this guide in futureeditions by completing the questionnaire andmaking suggestions for changes and additions.The evaluation can be sent to us by mail orelectronically submitted through the Internet sitelisted on the form.

How To Use This Guide

Page 6: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)ii

Note on Measurement andFormat

In developing this guide, metric units ofmeasurement were employed. In a fewexceptions, notably within the “Materials andTools” lists, British units have been listed. In theUnited States, metric-sized parts such as screwsand wood stock are not as accessible as theirBritish equivalents. Therefore, British units havebeen used to facilitate obtaining requiredmaterials.

The main text of this guide uses large printlocated in a wide column. Subjects relating tomathematics, physical science, and technologyare highlighted in bold. Definitions, questions fordiscussion, and examples are provided in smallerprint in the narrow column of each page. Eacharea highlighted in the text has a correspondingsection in the narrow column. This correspondingsection first lists applicable Mathematics andScience Content Standards, indicated by gradelevel: ∆ Grades 5–8, o Grades 9-12. We haveattempted to position the appropriate discussionas close as possible to the relevant highlightedtext. A key word or phrase in each margindiscussion is also highlighted for ease inidentifying related text.

Page 7: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏) iii

Table of ContentsIntroduction

First, What is Gravity? ............................................................................................... 1What is Microgravity? ................................................................................................ 1Creating Microgravity ................................................................................................ 3

Drop Facilities ..................................................................................................... 7Aircraft ................................................................................................................ 8Rockets ............................................................................................................... 9Orbiting Spacecraft ........................................................................................... 10

Microgravity Science Primer .......................................................................................... 13The Microgravity Environment of Orbiting Spacecraft ............................................. 15Biotechnology .......................................................................................................... 16

Protein Crystal Growth ..................................................................................... 18Mammalian Cell and Tissue Culture ................................................................ 19Fundamental Biotechnology ............................................................................ 21

Combustion Science ............................................................................................... 21Premixed Gas Flames ..................................................................................... 25Gaseous Diffusion Flames ............................................................................... 25Liquid Fuel Droplets and Sprays ...................................................................... 25Fuel Particles and Dust Clouds........................................................................ 26Flame Spread Along Surfaces ......................................................................... 26Smoldering Combustion................................................................................... 27Combustion Synthesis ..................................................................................... 27

Fluid Physics ........................................................................................................... 28Complex Fluids ................................................................................................ 29Multiphase Flow and Heat Transfer ................................................................. 31Interfacial Phenomena ..................................................................................... 32Dynamics and Stability ..................................................................................... 33

Fundamental Physics .............................................................................................. 34Materials Science .................................................................................................... 37

Electronic Materials .......................................................................................... 39Glasses and Ceramics ..................................................................................... 40Metals and Alloys ............................................................................................. 41Polymers .......................................................................................................... 43

Microgravity Research and Exploration ................................................................... 44

Page 8: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)iv

Microgravity Science Space Flights ...............................................................................46International Microgravity Laboratory-1, January 1992 .......................................49United States Microgravity Laboratory-1, June 1992 ..........................................49Spacelab-J, September 1992 ..............................................................................51United States Microgravity Payload-1, October 1992 .........................................52United States Microgravity Payload-2, March 1994 ............................................53International Microgravity Laboratory-2, July 1994 .............................................55United States Microgravity Laboratory-2, October 1995 .....................................57United States Microgravity Payload-3, February 1996 ........................................59Life and Microgravity Spacelab, June 1996 ........................................................62Shuffle/Mir Science Program, March 1995 to May 1998 .....................................64

Future Directions ............................................................................................................68

Glossary .........................................................................................................................71

Activities .........................................................................................................................75

NASA Resources for Educators ...................................................................................167

NASA Educational Materials ........................................................................................168

Page 9: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

1

IntroductionSpace flight is important for rnany reasons. Spaceflight carries scientific instruments and humanresearchers high above the ground, permitting usto see Earth as a planet and to study the complexinteractions of atmosphere, oceans, land, energy,and living things. Space flight lifts scientificinstruments above the filtering effects of theatmosphere, making the entire electromagneticspectrum available and allowing us to see moreclearly the distant planets, stars, and galaxies.Space flight permits us to travel directly to otherworlds to see them close up and sample theircompositions. Finally, space flight allowsscientists to investigate the fundamental states ofmatter—solids, liquids, and gases—and theforces that affect them in a microgravityenvironment.

The study of the states of matter and theirinteractions in microgravity is an excitingopportunity to expand the frontiers of science.Areas of invest’gation include biotechnology,combustion scie,lce, fluid physics, fundamentalphysics, materials science, and ways in whichthese areas of research can be used to advanceefforts to explore the Moon and Mars.

Microgravity is the subject of this teacher’s guide.This publication identifies the underlyingmathematics, physics, and technology principlesthat apply to microgravity. Supplementaryinformation is included in other NASA educationalproducts.

First, What is Gravity?Gravitational attraction is a fundamental propertyof matter that exists throughout the knownuniverse. Physicists identify gravity as one of thefour types of forces in the universe. The othersare the strong and weak nuclear forces and theelectromagnetic force.

Mathematics Standards

o Mathematical Connectionso Mathematics as Communication

∆ Number and Number Relationships∆ Number Systems and Number Theory

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

The electromagnetic spectrum is generally separated intodifferent radiation categories defined by frequency (units ofHertz) or wavelength (units of meters). Wavelength is commonlyrepresented hy the symbol λ.

Example:

NameXraysUltravioletVisible LightInfraredMicrowaveTelevisionAM Radio

Mathematics Standards

∆ o Algebrao Conceptual Underpinnings of Calculus

Geometryo Geometry from an Algebraic Perspective

∆ o Mathematical Connections∆ o Mathematics as Reasoning

o Trigonometry

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

An impressed force is an action exerted upon a body,in order to change its state, either of rest, or of uni-

ApproximateWavelength (m)= 10-15 to 10-9

= 10-8 to 10-7

= 10-7 to 10-6

= 10-6 to 10-3

= 10-3 to 10-1

= 10-1 to 1= 10-2 to 103

Page 10: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

2

form motion in a straight line. A body force acts on the entiremass as a result of an external effect not due to direct contact;gravity is a body force. A surface force is a contact force that actsacross an internal or external surface of a body.

Mathematics Standards

∆ o Algebrao Conceptual Underpinnings of Calculus

∆ Geometryo Geometry from an Algebraic Perspective

∆ o Mathematical Connections∆ o Mathematics as Reasoning

o Trigonometry

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

Velocity is the rate at which the position of an object changeswith time; it is a vector quantity. Speed is the magnitude ofvelocity.

Mathematics Standards

∆ o Mathematical Connections∆ o Mathematics as Reasoning

Science Standards

∆ o History and Nature of Science∆ o Science as Inquiry∆ o Unifying Concepts and Processes

Newton’s discovery of the universal nature of the force ofgravity was remarkable. To take the familiar force that makes anapple fall to Earth and be able to recognize it as the same forcethat keeps the planets on their quiet and predictable pathsrepresents one of the major achievements of human intellectualendeavor. This ability to see beyond the obvious and familiar isthe mark of a true visionary. Sir Issac Newton’s pioneering workepitomizes this quality.

Mathematics Standards

∆ o Algebra∆ Computation and Estimation

o Functions∆ o Mathematical as Communication∆ Number and Number Relationships∆ Patterns and Functions

Science Standards

∆ o Unifying Concepts and Processes

More than 300 years ago the great Englishscientist Sir Isaac Newton published theimportant generalization that mathematicallydescribes this universal force of gravity. Newtonwas the first to realize that gravity extends wellbeyond the domain of Earth. The basis of thisrealization stems from the first of three laws heformulated to describe the motion of objects. Partof Newton’s first law, the law of inertia, states thatobiects in motion travel in a straight line at aconstant velocity unless acted upon by a netforce. According to this law, the planets in spaceshould travel in straight lines. However, as earlyas the time of Aristotle, scholars knew that theplanets travelled on curved paths. Newtonreasoned that the closed orbits of the planets arethe result of a net force acting upon each of them.That force, he concluded, is the same force thatcauses an apple to fall to the ground—gravity.

Newton’s experimental research into the force ofgravity resulted in his elegant mathematicalstatement that is known today as the Law ofUniversal Gravitation. According to Newton, everymass in the universe attracts every other mass.The attractive force between any two objects isdirectly proportional to the product of the twomasses being considered and inverselyproportional to the square of the distanceseparating them. If we let F represent this force, rrepresent the distance between the centers of themasses, and m1 and m2 represent the magnitudesof the masses, the relationship stated can bewritten symbolically as:

From this relationship, we can see that the greaterthe masses of the attracting objects, the greaterthe force of attraction between them. We can alsosee that the farther apart the objects are fromeach other, the less the attraction. If the distancebetween the objects doubles, the attractionbetween them diminishes by a factor of four, andif the distance triples, the attraction is only one-ninth as much.

Page 11: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

3

The eighteenth-century English physicist HenryCavendish later quantified Newton’s Law ofUniversal Gravitation. He actually measured thegravitational force between two one kilogrammasses separated by a distance of one meter.This attraction was an extremely weak force, butits determination permitted the proportionalrelationship of Newton’s law to be converted intoan equality. This measurement yielded theuniversal gravitational constant, G. Cavendishdetermined that the value of G is 6.67 x 10-11 Nm2/kg2. With G added to make the equation, theLaw of Universal Gravitation becomes:

What is Microgravity?

The presence of Earth creates a gravitational fieldthat acts to attract objects with a force inverselyproportional to the square of the distancebetween the center of the object and the center ofEarth. When we measure the acceleration of anobject acted upon only by Earth’s gravity at theEarth’s surface, we commonly refer to it as one gor one Earth gravity. This acceleration isapproximately 9.8 meters per second squared (m/s2). The mass of an object describes how muchthe object accelerates under a given force. Theweight of an object is the gravitational forceexerted on it by Earth. In British units (commonlyused in the United States), force is given in unitsof pounds. The British unit of masscorresponding to one pound force is the slug.

While the mass of an object is constant and theweight of an object is constant (ignoringdifferences in g at different locations on theEarth’s surface), the environment of an objectmay be changed in such a way that its apparentweight changes. Imagine standing on a scale in astationary elevator car. Any vertical accelerationsof the elevator are considered to be positive

indicates proportionality

indicates equality

is an expression

is an equation

Mathematics Standards

∆ o Algebra∆ o Mathematical Connections∆ o Mathematics as Communication∆ Measurement

Science Standards

∆ o Science and Technology∆ o Science as Inquiry∆ o Unifying Concepts and Processes

The internationally recognized Systeme International (Sl) is asystem of measurement units. The Sl units for length (meter) andmass (kg) are taken from the metric system. Many dictionariesand mathematics and science textbooks provide conversion tablesbetween the metric system and other systems of measurement.Units conversion is very important in all areas of life. forexample in currency exchange, airplane navigation, and scientificresearch.

Units Conversion Examples1 kg ≅ 2.2lb 1 in = 2.54cm1 liter≅ 1 qt 1 yd ≅ 0.9 m

Questions for Discussion• What common objects have a mass of about 1 kg?• What are the dimensions of this sheet of paper in cm and

inches?• How many liters are there in a gallon?

Mathematics Standards

∆ Computation and Estimation∆ o Mathematics as Communication∆ Number and Number Relationships∆ Number Systems and Number Theory

Page 12: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

4

Science Standards

∆ o Science as Inquiry∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

Scientific notation makes it easier to read, write, and manipulatenumbers with many digits. This is especially useful tor makingquick estimates and for indicating the number of significantfigures.

Examples:0.001 = 10-3

10 = 101

1000 = 103

Which is bigger, 6 x 10-3 or 8 x 10-4? 6 x 103 or 8 x 104?How much bigger?

Mathematics Standards

∆ o Mathematical Connections∆ o Mathematics as Reasoning

Science Standards

∆ o Science and Technology∆ o Science as Inquiry∆ o Unifying Concepts and Processes

Questions for Discussion• How does a scale work ?• What does a scale measure?• How many different kinds of scales can you list?• Do they need gravity for them to work?• Would you get different results on the Moon or Mars?• How can you measure the mass of an object in

microgravity?

upwards. Your weight, W, is determined by yourmass and the acceleration due to gravity at yourlocation.

If you begin a ride to the top floor of a building,an additional force comes into play due to theacceleration of the elevator. The force that thefloor exerts on you is your apparent weight, P, themagnitude of which the scale will register. Thetotal force acting on you is F=W+P=mae, where aeis the acceleration of you and the elevator andW=mg. Two example calculations of apparentweight are given in the margin of the next page.Note that if the elevator is not accelerating thenthe magnitudes W and P are equal but thedirection in which those forces act are opposite(W=-P). Remember that the sign (positive ornegative) associated with a vector quantity, suchas force, is an indication of the direction in whichthe vector acts or points, with respect to a definedframe of reference. For the reference framedefined above, your weight in the example in themargin is negative because it is the result of anacceleration (gravity) directed downwards(towards Earth).

Imagine now riding in the elevator to the top floorof a very tall building. At the top, the cablessupporting the car break, causing the car and.you to fall towards the ground. In this example,we discount the effects of air friction and elevatorsafety mechanisms on the falling car. Yourapparent weight P=m(ae-g)=(60 kg)(-9.8 m/s2-(-9.8 m/s2)) = O kg m/s2; you are weightless. Theelevator car, the scale, and you would all beaccelerating downward at the same rate, which isdue to gravity alone. If you lifted your feet off theelevator floor, you would float inside the car. Thisis the same experiment that Galileo is purportedto have performed at Pisa, Italy, when he droppeda cannonball and a musketball of different massat the same time from the same height. Both ballshit the ground at the same time, just as theelevator car, the scale, and you would reach theground at the same time.

Page 13: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

5

Normalweight

Heavierthan normal

Lighterthan normal

No apparentweight

Acceleration and weight

The person in the stationary elevator car experiences normalweight. In the car immediately to the right, apparent weightincreases slightly because of the upward acceleration.Apparent weight decreases slightly in the next car because ofthe downward acceleration. No weight is measured in the lastcar on the right because of free fall.

For reasons that are discussed later, there aremany advantages to performing scientificexperiments under conditions where the apparentweight of the experiment system is reduced. Thename given to such a research environment ismicrogravity. The prefix micro- (m) derives fromthe original Greek mikros meaning small. By thisdefinition, a microgravity environment is one inwhich the apparent weight of a system is smallcompared to its actual weight due to gravity. Aswe describe how microgravity envifonments canbe produced, bear in mind that many factorscontribute to the experienced accelerations andthat the quality of the microgravity environmentdepends on the mechanism used to create it. Inpractice, the microgravity environments used byscientific researchers range from about onepercent of Earth’s gravitational acceleration(aboard aircraft in parabolic flight) to better thanone part in a million (for example, onboard Earth-orbiting research satellites).

Quantitative systems of measurement, such asthe metric system, commonly use micro- to meanone part in a million. Using that definition, theacceleration experienced by an object in a

Mathematics Standards

∆ o Algebra∆ Computational and Estimation

o Conceptual Underpinnings of Calculus∆ o Mathematical Connections∆ o Mathematics as Problem Solving∆ Measurement

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Science as Inquiry∆ o Unifying Concepts and Processes

F=W+P=mae

Rewriting yields P=mae-mg=m(a

e- g).

If your mass is 60 kg and the elevator is aeceleratingupwards at 1 m/s2, your apparent weight isP=60 kg (+1 m/s2-(-9.8 m/s2))=+648 kg m/s2

while your weight remainsW=mg=(60 kg)(-9.8 m/s2)=-588 kg m/s2.If the elevator aceelerates downwards at 0.5 m/s2,your apparent weight isP=60 kg (-0.5 m/s2-(-9.8 m/s2))=+558 kg m/s2.

Mathematics Standards

∆ o Mathematics as Communications∆ o Mathematics as Reasoning

Science Standards

∆ o Science as Inquiry∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

1 micro-g or 1 µg = 1 x 10-6 g

Questions for Discussion• What other eommon prefixes or abbreviations tor powers of

ten do you know or ean you find ?• In what everyday places do you see these used ?

Grocery stores, farms, laboratories, sporting facilities,pharmacies, machine shops.

Common prefixes for powers of ten:10-9 nano- n10-3 milli- m102 centi- c103 kilo- k106 mega- M109 giga- G

Page 14: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

6

Mathematics Standards

∆ o Algebra∆ Computation and Estimation

o Conceptual Underpinnings of Calculuso Discrete Mathematics

∆ o Mathematical Connections∆ o Mathematics as Problem Solving∆ o Mathematics as Reasoning∆ Number and Number Relationships

Science Standards

∆ o Unifying Concepts and Processes

Calculate the times in these examples. Teachers canuse these examples at several different scholasticlevels.

Provide the equation as:

Provide the equation as d=(1/2) as t2, and have thestudents re-order the equation.

Making measurements and calculating results involvethe concepts of accuracy and precision, significant figures, andorders of magnitude. With these concepts in mind, are the droptimes given in the text “correct”?

Mathematics Standards

∆ o Algebra∆ Computation and Estimation∆ o Mathematical Connections∆ o Mathematics as Problem Solving∆ o Mathematics as Reasoning∆ Measurement

Science Standards

∆ o Science and Technology∆ o Science as Inquiry∆ o Unifying Concepts and Processes

Questions for Discussion• How far away is the Mooon?• How far away is the center of Earth from the center

of the Moon?• Why did we ask the previous question?• How far away is the surface of Earth from the surface

of the Moon• What are the elevations of different features of

Earth and the Moon?• How are elevations measured?

microgravity environment would be one-millionth(10-6) of that experienced at Earth’s surface. Theuse of the term microgravity in this guide willcorrespond to the first definition. For illustrativepurposes only, we provide the following simpleexample using the quantitative definition. Thisexample attempts to provide insight into whatmight be expected if the local accelerationenvironment would be reduced by six orders ofmagnitude from 1 g to 10-6 g,

If you dropped a rock from a roof that was fivemeters high, it would take just one second toreach the ground. In a reduced gravityenvironment with one percent of Earth’sgravitational pull, the same drop would take 10seconds. In a microgravity environment equal toone-millionth of Earth’s gravitational pull, thesame drop would take 1,000 seconds or about 17minutes!

Researchers can create microgravity conditions intwo ways. Because gravitational pull diminisheswith distance, one way to create a microgravityenvironment (following the quantitative definition)is to travel away from Earth. To reach a pointwhere Earth’s gravitational pull is reduced toonemillionth cf that at the surface, you wouldhave to travel into space a distance of 6.37million kilometers from Earth (almost 17 timesfarther away than the Moon, 1400 times thehighway distance between New York City and LosAngeles, or about 70 million football fields). Thisapproach is impractical, except for automatedspacecraft, because humans have yet to travelfarther away from Earth than the distance to theMoon. However, freefall can be used to create amicrogravity environment consistent with ourprimary definition of microgravity. We discussthis in the next section.

Page 15: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

7

Creating Microgravity

As illustrated in the elevator examples in theprevious section, the effects of gravity (apparentweight) can be removed quite easily by puttinganything (a person, an object, an experiment) intoa state of freefall. This possibility of using Earth’sgravity to remove the effects of gravity within asystem were not always evident. Albert Einsteinonce said, “I was sitting in a chair in the patentoffice at Bern when all of a sudden a thoughtoccurred to me: ‘If a person falls freely, he will notfeel his own weight.’ I was startled. This simplethought made a deep impression on me. Itimpelled me toward a theory of gravitation.”Working with this knowledge, scientists involvedin early space flights rapidly concluded thatmicro-gravity experiments could be performed bycrew members while in orbit.

Gravity and Distance

The inverse square relationship between gravitational force anddistance can be used to determine the acceleration due to gravityat any distance from the center of Earth, r.

F = Gmem/r

e2 force of gravity due to Earth on a mass,

m, at Earth’s surfaceF = mg ➔ g = Gm

e/r

e2

F = Gmem/r2 force of gravity due to Earth on a mass,

m, at a distance, r, from Earth’s centerF = ma ➔ a = Gm

e/r2

gre2 = ar2

a = gre2/r2 acceleration due to Earth’s gravity at

distance, r, from Earth’s center

A typical altitude for a Space Shuttle Orbiter orbit is 296 km. TheEarth’s mean radius is 6.37x106 m. The acceleration due togravity at the Orbiter’s altitude is

a = 9.8 m/s2 (6.37x106 m)2 / (6.67x106 m)2 = 8.9 m/s2

This is about 90% of the acceleration due to gravity at Earth’ssurface. Using the same equations, you can see that to achieve amicrogravity environment of 10-6 g by moving away from Earth,a research laboratory would have to be located 6.37x109 m fromthe center of Earth.

Page 16: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

8

Mathematics Standards

∆ o Algebra∆ Computation and Estimation

o Conceptual Underpinnings of Calculuso Discrete Mathematicso Functions

∆ o Mathematical Connections∆ o Mathematics as Problem Solving∆ o Mathematics as Reasoning∆ Patterns and Functions∆ o Statistics

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Science as Inquiry∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

Questions for Discussion• What is the functional relationship between acceleration,

distance, and time?

Use the four sets of drop facility data points given in the textand the additional data set (0 meters, 0 seconds). What doesthe (0 meters, 0 seconds) data set represent? Why is it a validdata set to use?

Suggested solution methods: Use different types of graphpaper Use a computer e urvefitting r)rogrnm Do a dimensionalanalysis.

• Knowing that g=9.8 m/s2, what equation can you write toincolporate acceleration, distance, and time?

• Assume it costs $5,000 per meter of height to build a droptower.

How much does it cost to build a drop tower to allow drops of1 second, 2 seconds, 4 seconds, 10 seconds?

Why does it cost so much more for the longer times?

What would be an inexpensive way to double low-gravity time in a drop tower?

Shoot the experiment package up from the bottom.

The use of orbiting spacecraft is one methodused by NASA to create microgravity conditions.In addition, four other methods of creating suchconditions are introduced here and we giveexamples of situations where the student canexperience microgravity.

Drop FacilitiesResearchers use high-tech facilities based on theelevator analogy to create micro-gravityconditions. The NASA Lewis Research Center hastwo drop facilities. One provides a 132 meterdrop into a hole in the ground similar to a mineshaft. This drop creates a reduced gravityenvironment for 5.2 seconds. A tower at Lewisallows for 2.2 second drops down a 24 meterstructure. The NASA Marshall Space Flight Centerhas a different type of reduced gravity facility.This 100 meter tube allows for drops of 4.5second duration. Other NASA Field Centers andother countries have additional drop facilities ofvarying sizes to serve different purposes. Thelongest drop time currently available (about 10seconds) is at a 490 meter deep vertical mineshaft in Japan that has been converted to a dropfacility. Sensations similar to those resulting froma drop in these reduced gravity facilities can beexperienced on freefall rides in amusement parksor when stepping off of diving platforms.

Schematic of the NASA Lewis Research Center 2.2 SecondDrop Tower.

Page 17: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

9

AircraftAirplanes are used to achieve reduced gravityconditions for periods of about 15 seconds. Thisenvironment is created as the plane flies on aparabolic path. A typical flight lasts two to threehours allowing experiments and crew members totake advantage of about forty periods ofmicrogravity. To accomplish this, the plane climbsrapidly at a 45 degree angle (this phase is calledpull up), traces a parabola (pushover), and thendescends at a 45 degree angle (pull out). Duringthe pull up and pull out segments, crew andexperiments experience accelerations of about 2g. During the parabola, net accelerations drop aslow as 1.5x10-2 g for about 15 seconds. Due tothe experiences of many who have flown onparabolic aircraft, the planes are often referred toas “Vomit Comets.” Reduced gravity conditionscreated by the same type of parabolic motiondescribed above can be experienced on the seriesof “floater” hills that are usually located at the endof roller coaster rides and when driving overswells in the road.

Parabolic Flight Characteristics

Mathematics Standards

o Conceptual Underpinnings of Calculuso Functions

∆ o Mathematical Connections∆ Patterns and Functions

Science Standards

∆ o Earth and Space Science∆ o Physical Science∆ o Unifying Concepts and Processes

Microgravity carriers and other spacecraft follow paths bestdescribed by conic sections. The aircraft and sub-orbital rocketstrace out parabolas. Orbiting spacecraft are free falling onelliptical paths. When a meteoroid is on a path that is influencedby Earth or any other planetary body but does not get capturedby the gravitational field of the body, its motion, as it approachesthen moves away from the body, traces out a hyperbolic path.

Page 18: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

10

Rocket Parabolic Flight Profile

Mathematics Standards

∆ o Algebra∆ Computation and Estimation

o Conceptual Underpinnings of Calculuso Discrete Mathematicso Functions

∆ o Mathematical Connections∆ o Mathematics as Problem Solving∆ o Mathematics as Reasoning∆ Number and Number Relationships

Science Standards

o Physical Science∆ o Science and Technology

o Science as Inquiryo Unifying Concepts and Processes

Questions for Discussion• How does the Shuttle stay in orbit? Use the following two

equations that descnbe the foree aeting on an object. The firstequation represents the force of gravity acting on the Shuttle.

Where:

F1

= Force of gravity acting on the Shuttle

G = Universal gravitational constant

me

= Mass of Earth

ms

= Mass of the Shuttle

r = Distance from center of Earth to the Shuttle

RocketsSounding rockets are used to create reducedgravity conditions for several minutes; they followsuborbital, parabolic paths. Freefall exists duringthe rocket’s coast: after burn out and beforeentering the atmosphere. Acceleration levels areusually around 10-5 g. While most people do notget the opportunity to experience theaccelerations of a rocket launch and subsequentfreefall, springboard divers basically launchthemselves into the air when performing divesand they experience microgravity conditions untilthey enter the water.

Orbiting SpacecraftAlthough drop facilities, airplanes, and rocketscan establish a reduced gravity environment, allthese facilities share a common problem. After afew seconds or minutes, Earth gets in the wayand freefall stops. To conduct longer scientificinvestigations, another type of freefall is needed.

To see how it is possible to establish microgravityconditions for long periods of time, one must firstunderstand what keeps a spacecraft in orbit. Askany group of students or adults what keepssatellites and Space Shuttles in orbit and youwill probably get a variety of answers. Twocommon answers are “The rocket engines keepfiring to hold it up,” and “There is no gravity inspace.”

Although the first answer is theoretically possible,the path followed by the spacecraft wouldtechnically not be an orbit. Other than the altitudeinvolved and the specific means of exerting anupward force, little difference exists between aspacecraft with its engines constantly firing andan airplane flying around the world. A satellitecould not carry enough fuel to maintain itsaltitude for more than a few minutes. The secondanswer is also wrong. At the altitude that theSpace Shuttle typically orbits Earth, thegravitational pull on the Shuttle by Earth is about90% of what it is at Earth’s surface.

F1 = G

mem

s

r2

Page 19: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

11

In a previous section, we indicated that IssacNewton reasoned that the closed orbits of theplanets through space were due to gravity’spresence. Newton expanded on his conclusionsabout gravity and hypothesized how an artificialsatellite could be made to orbit Earth. Heenvisioned a very tall mountain extending aboveEarth’s atmosphere so that friction with the airwould not be a factor. He then imagined a cannonat the top of that mountain firing cannonballsparallel to the ground. Two forces acted uponeach cannonball as it was fired. One force, due tothe explosion of the black powder, propelled thecannonball straight outward. If no other forcewere to act on the cannonball, the shot wouldtravel in a straight line and at a constant velocity.But Newton knew that a second force would acton the cannonball: gravity would cause the pathof the cannonball to bend into an arc ending atEarth’s surface.

The second equation represents the force acting on the Shuttlethat causes a centripetal acceleration,

This is an expression of Newton’s second law, F=ma.

F2

= Force acting on the Shuttle that causes uniformcircular motion (with centripetal acceleration)

v = Velocity of the Shuttle

These two forces are equal: Fl=F

2

V =

In order to stay in a circular orbit at a given distance from thecenter of Earth, r, the Shuttle must travel at a precise velocity, v.

• How does the Shuttle change its altitude? From a detailedequation relating the Shuttle velocity with the Shuttle altitude,one can obtain the following simple relationship for a circularorbit. Certain simplifying assumptions are made in developingthis equation: 1) the radius of the Shuttle orbit is nearly thesame as the radius of Earth, and 2) the total energy of theShuttle in orbit is due to its kinetic energy, 1/2 mv2; the changein potential energy associated with the launch is neglected.

∆r = ∆v

τ = orbital period. the time it takes thc Shuttle to completeone revolution around Earth

=

∆v = the change in Shuttle velocity∆r = the change in Shuttle altitude

v2

r

G =m

em

s

r2

msv2

r

v2 =Gm

e

r

τπ

2 π r 3/2

(Gme) 1/2

Gm

r

e

Illustration from Isaac Newton, Principia, VII,Book III, p. 551.

Page 20: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

12

For example:

Consider a Shuttle in a circular orbit at 160 nautical miles (296.3km) altitude. Determine the new altitude caused by the Shuttlefiring a thruster that increases its velocity by I m/s.

First, calculate the orbital period, X, from the above equation.

τ = 2π(re+2.96 x l05 m)3/2

(Gme) 1/2

= 2π(6.37 x 106m+2.96 x 105 m)3/2

(6.67 x 10-11 m3 x 5.98 x1024kg)l/2

s2kg

= 5.41 x 103 s

Next, use the period and the applied velocity change to calculatethe altitude change.

τ

= 5.41x103s

= 1.72xl03 m

This altitude change is actually seen on the opposite side of theorbit. In order to make the orbit circular at the new altitude, theShuttle needs to apply the same ∆v at the other side of the orbit.

In the discussion and example just given, we state that theequations given are simple approximations of more complexrelationships between Shuttle velocity and altitude. The morecomplex equations are used by the Shuttle guidance andnavigation teams who track the Shuttles’ flights. But theequations given here can be used for quick approximations of thetypes of thruster firings needed to achieve certain altitudechanges. This is helpful when an experiment team may want torequest an altitude change. Engineers supporting the experimentteams can determine approximately how much propellant wouldbe required for such an altitude change and whether enoughwould be left for the required de-orbit burns. In this way, theengineers and experiment teams can see if their request isrealistic and if it has any possibility of being implemented.

Newton considered how additional cannonballswould travel farther from the mountain each timethe cannon fired using more black powder. Witheach shot, the path would lengthen and soon thecannonballs would disappear over the horizon.Eventually, if one fired a cannon with enoughenergy, the cannonball would fall entirely aroundEarth and come back to its starting point. Thecannonball would be in orbit around Earth.Provided no force other than gravity interferedwith the cannonball’s motion, it would continuecircling Earth in that orbit.

This is how the Space Shuttle stays in orbit. Itlaunches on a path that arcs above Earth so thatthe Orbiter travels at the right speed to keep itfalling while maintaining a constant altitude abovethe surface. For example, if the Shuttle climbs toa 320 kilometer high orbit, it must travel at aspeed of about 27,740 kilometers per hour toachieve a stable orbit. At that speed and altitude,the Shuttle executes a falling path parallel to thecurvature of Earth. Because the Space Shuttle isin a state of freefall around Earth and due to theextremely low friction of the upper atmosphere,the Shuttle and its contents are in a high-qualitymicrogravity environment.

∆r=π

(1 m/s )π

∆v

Page 21: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

13

MicrogravityScience PrimerWe experience many manifestations of gravity ona day to day basis. If we drop something, it fallstoward Earth. If we release a rock in a container ofwater, the rock settles to the bottom of the con-tainer. We experience other effects of gravityregularly, although we may not think of gravity asplaying a role.

Consider what happens when a container of wateris heated from below. As the water on the bottomis heated by conduction through the container, itbecomes less dense than the un-heated, coolerwater. Because of gravity, the cooler, more densewater sinks to the bottom of the container and theheated water rises to the top due to buoyancy. Acirculation pattern is produced that mixes the hotwater with the colder water. This is an example ofbuoyancy driven (or gravity driven) convection.The convection causes the water to be heatedmore quickly and uniformly than if it were heatedby conduction alone. This is the same densitydriven convection process to which we refer whenwe state matter-of-factly that”hot air rises.”

In addition to mixing, density differences can alsocause things to differentially settle through aprocess called sedimentation. In this process, themore dense components of mixtures ofimmiscible fluids or solid particles in fluids sett’eto the bottom of a container due to gravity. If youfill a bucket with very wet mud, and then leave thebucket sitting on the ground, over time the moredense soil particles will sink to the bottom of thebucket due to gravity, leaving a layer of water ontop. When you pick up a bottle of Italian saladdressing from the grocery store shelf, you seeseveral different layers in the bottle. The densesolids have settled to the bottom, the vinegarforms a middle layer, and the least dense oil is ontop.

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

Heat transfer occurs through one of three processes or acombination of the three. Conduction is the flow of heat througha body from an area of higher temperature to an area of lowertemperature. Molecules in the hot region increase theirvibrational energy as they are heated. As they collide withmolecules with lower vibrational energy (cooler ones). some ofthe vibrational energy is passed to the cooler ones, their energy isincrcased. and heat is passed on.

Heat transfer by convection is the movement of heat by motionof a fluid. This motion can he the result of some force, such as apump circulating heated water. and is referred to as forcedconvection. If the motion is the result of difterences in density(thermal or compositional). the convection is referred to asbuoyancy-driven, density-driven. or natural convection.

Radiation is the emission of energy trom the surface of a body.Energy is emitted in the form of electromagnetic waves orphotons (packets of light). The character (wavelength. energy ofphotons, etc.) of the radiation depends on the temperature.surface area. and characteristics of the body emitting the energy.Electromagnetic waves travel with the speed of light throughempty space and are absorbed (and/or reflected) by objects theyfall on, thus transferring heat. An excellent example of radiativeheating is the sun’s heat that we experience on Earth.

Mathemathics Standards

∆ o Mathematical Conneclions

Science Standards

∆ o Earth and Space Science∆ o Physical Science∆ o Unifying Concepts and Processes

The mass of a body divided hy its volume is its average density.

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

When two or more liquids are immiscible they do not mixchemically.

Page 22: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

14

Density Table Units (kg/m3)

Interstellar space 10-21 - 10-18

Atmosphere at normal altitudeof Space Shuttle in orbit 1-4x10-11

Air at 0°C and 1 atm 1.3Carbon Dioxide 1.9Balsa 110-140Bone 170-200Cork 220-260The Larch 500-560Lithium 530Applewood 660-840Peat Blocks 840Ice 920Olive Oil 920Sodium 970Water at 0°C and 1 atm 1000Rock Salt 2180Graphite 2300-2700Alunıinum 2700Basalt 2400-3100Talc 2700-2800Dolomite 2830Diamond 3010-3520Average density of Earth 5520Iron 7860Lead 11340Irdium 22400Osmium 22500Uranium nucleus 3x1017

Neutron star (center) 1017-1018

Mathematics Standards

∆ o Algebrao Functions

∆ Geometryo Geometry from a Synthetic Perspective

∆ o Mathematical Connections∆ o Mathematics as Communication∆ o Mathematics as Problem Solving∆ Measurement

o Trigonometry

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

Gravity can also mask some phenomena thatscientists wish to study. An example is theprocess of diffusion. Diffusion is the interminglingof solids, liquids, and gases due to differences incomposition. Such intermingling occurs in manysituations, but diffusion effects can be easilyhidden by stronger convective mixing. As anexample, imagine a large room in which all aircirculation systems are turned off and in which agroup of women are spaced ten feet apartstanding in a line. If an open container ofammonia were placed in front of the first womanin line and each woman raised her hand when shesmelled the ammonia, it would take aconsiderable amount of time before everyoneraised her hand. Also, the hand raising wouldoccur sequentially along the line from closest tothe ammonia to furthest from the ammonia. If thesame experiment were performed with a fancirculating air in the room, the hands would beraised more quickly, and not necessarily in thesame order. In the latter case, mixing of theammonia gas with the air in the room is due toboth diffusion and convection (forced convectiondue to the fan) and the effects of the twoprocesses cannot be easily separated. In a similarmanner, buoyancy driven convection can maskdiffusive mixing of components in scientificexperiments.

Some behavior of liquids can also be masked bygravity. If you pour a liquid into a container onEarth, the liquid conforms to the bottom of thecontainer due to gravity. Depending on the shapeof the container and on the properties of thecontainer and the liquid, some of the liquid maycreep up the walls or become depressed alongthe walls due to the interrelated phenomena ofsurface tension, adhesion, cohesion, andcapillarity.

The resulting curved surface may be familiar toanyone who has measured water in a smalldiameter glass container (the water cupsupward) or has looked at the level of mercury in aglass thermometer (the mercury cupsdownward). The distance the contact

Page 23: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

15

line between the liquid and the container movesup or down the container wall is affected bygravity.

Experiments performed on Earth often takeadvantage of the effects of gravity discussed. Formany experiments, however, these effects tend tomake the execution of experiments or the analysisof experimental results difficult and sometimeseven impossible. Therefore, many researchersdesign experiments to be performed undermicrogravity conditions. The different scientificresearch areas that are studied in microgravityinclude biotechnology, combustion science, fluidphysics, fundamental physics, and materialsscience. Each of these areas, or disciplines, isdiscussed below. The discipline is defined, someof the specific effects of gravity that illustrate thebenefits of microgravity research are discussed,and some examples of current research arepresented. In addition, a brief discussion of themicrogravity environment of orbiting spacecraft isprovided as is an introduction to the applicationof microgravity research to the exploration anddevelopment of space.

The MicrogravityEnvironment ofOrbiting SpacecraftWhile freefall reduces the effects of gravity, beingin an orbiting laboratory introduces otheraccelerations that cause effects that areindistinguishable from those due to gravity. Whena spacecraft is in orbit around Earth, the orbit isactually defined by the path of the center of massof the spacecraft around the center of Earth. Anyobject in a location other than on the linetraversed by the center of mass of the spacecraftis actually in a different orbit around Earth.Because of this, all objects not attached to thespacecraft move relative to the orbiter center ofmass. Other relative motions of unattachedobjects are related to aerodynamic drag on the

Capillarity can be defined as the attraction a fluid has for itselfversus the attraction it has for a solid surface (usually the fluid’scontainer). Thc surface tension σ in a liquid-liquid or liquid-gassystem is the fluids’ tendency to resist an increase in surface area.Surface tension is temperature dependent. Surface tension,capillarity, adhesion, and cohesion work together to drive thecontact angle θ between a solid-liquid interface and liquid-liquidinterface when a small diameter tube is dipped into a liquid.When the contact angle θ=0, the liquid “wets” the tubccompletely. When θ<90° (an acute angle), the liquid rises in thetube; when θ>90° (an obtuse angle). the liquid is depressed in thetube and does not wet the walls. The distance belween the liquidsuri’ace in the container and in the tube is h=2<σcosθ/rρg wherer is the radius of the tube (D/2), ρ is the density of the liquid, andg is the acceleration due to gravity.

Mathematics Standards

o Functions∆ Geometry

o Geometry from a Synthetic Perspective

Science Standards

∆ o Science and Technology∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

Something that is concave is curved inward like the inner surfaceof a sphere. Something that is convex is curved like the outersurfiace of a sphere. A variety of concave and convex lenses andmirrors are used in the design of eyeglasses, magnifying glasses,cameras, microscopes, and telescopes. In the cxample in the text,water cupping upward produces a concave surface; mercurycupping downward produces a convex surface.

θh

D

ρ

h

θ

ρ

D

Page 24: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

16

Mathematics Standards

∆ Computation and Estimation∆ o Mathematical Connections∆ o Mathematics as Communication∆ Measurement

Science Standards

Grades 5-8 (∆); Grades 9-12 (o)

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

Quasi-steady accelerations in spacecraft are related to theposition in the spacecraft, aerodynamic drag, and vehiclerotation. For the Space Shuttle Orbiters, these accelerations areon the order of lx10-6 g and vary with the orbital frequency.

Mathematics Standards

∆ Computation and Estimation∆ o Mathematical Connections∆ o Mathematics as Communication∆ Measurement

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

g-jitter indicates the vibrations expenenced by microgravityexpenments (for example on parabolic aircraft and the SpaceShuttle) that cause effects similar to those that would be causedby a time-varying gravitational field.

The quasi-steady microgravity environment on the OrbiterColumbia shows the effiects of variations in Earth’s atmosphericdensity. The primary contribution to the variation is the day/nightdiffierence in atmospheric density. The plot shows that the dragon the Orbiter varies over a ninety minute orbit.

vehicle and spacecraft rotations. A spacecraft inlow-Earth orbit experiences some amount of dragdue to interactions with the atmosphere. Anobject within the vehicle, however, is protectedfrom the atmosphere by the spacecraft itself anddoes not experience the same deceleration thatthe vehicle does. The floating object andspacecraft therefore are moving relative to eachother. Similarly, rotation of the spacecraft due toorbital motion causes a force to act on objectsfixed to the vehicle but not on objects freelyfloating within it. On average for the SpaceShuttles, the quasi-steady accelerationsresulting from the sources discussed above(position in the spacecraft, aerodynamic drag,and vehicle rotation) are on the order of 1x1 0-6 g,but vary with time due to variations in theatmospheric density around Earth and due tochanges in Shuttle orientation.

In addition to these quasi-steady accelerations,many operations on spacecraft cause vibrationsof the vehicle and the payloads (experimentapparatus). These vibrations are often referred toas g-jitter because their effects are similar tothose that would be caused by a time-varyinggravitational field. Typical sources for vibrationsare experiment and spacecraft fans and pumps,motion of centrifuges, and thruster firings. With acrew onboard to conduct experiments, additionalvibrations can result from crew activities.

The combined acceleration levels that result fromthe quasi-steady and vibratory contributions aregenerally referred to as the microgravityenvironment of the spacecraft. On the SpaceShuttles, the types of vibration-causingoperations discussed above tend to create acumulative background microgravity environmentof about 1x10-4 g, considering contributions forall frequencies below 250 Hz.

BiotechnologyBiotechnology is an applied biological sciencethat involves the research, manipulation, and

Page 25: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

17

manufacturing of biological molecules, tissues,and living organisms. With a critical andexpanding role in health, agriculture, andenvironmental protection, biotechnology isexpected to have a significant impact on oureconomy and our lives in the next century.Microgravity research focuses on three principalareas—protein crystal growth, mammalian celland tissue culture, and fundamentalbiotechnology.

Gravity significantly influences attempts to growprotein crystals and mammalian cell tissue onEarth. Initial research indicates that proteincrystals grown in microgravity can yieldsubstantially better structural information thancan be obtained from crystals grown on Earth.Proteins consist of thousands—or in the case ofviruses, millions—of atoms, which are weaklybound together, forming large molecules. OnEarth, buoyancy-induced convection andsedimentation may inhibit crystal growth. Inmicrogravity, convection and sedimentation aresignificantly reduced, allowing for the creation ofstructurally better and larger crystals.

The absence of sedimentation means that proteincrystals do not sink to the bottom of their growthcontainer as they do on Earth. Consequently, theyare not as likely to be affected by other crystalsgrowing in the solution. Because convective flowsare also greatly reduced in microgravity, crystalsgrow in a much more quiescent environment,which may be responsible for the improvedstructural order of space-grown crystals.Knowledge gained from studying the process ofprotein crystal growth under microgravityconditions will have implications for proteincrystal growth experiments on Earth.

Research also shows that mammalian cells—particularly normal cells—are sensitive toconditions found in ground-based facilities usedto culture (grow) them. Fluid flows caused bygravity can separate the cells from each other,

Protein crystals grown in microgravity can haveregular, simple shapes and a more highly orderedinternal structure than those grown on Earth.

1 g µ g

Page 26: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

18

severely limiting the number of cells that willaggregate (come and stay together). But tissuesamples grown in microgravity are much largerand more representative of the way in whichtissues are actually produced inside the humanbody. This suggests that better control of thestresses exerted on cells and tissues can play animportant role in their culture. These stresses aregreatly reduced in microgravity.

Protein Crystal GrowthThe human body contains over 100,000 differentproteins. These proteins play important roles inthe everyday functions of the body, such as thetransport of oxygen and chemicals in the blood,the formation of the major components of muscleand skin, and the fighting of disease. Researchersin this area seek to determine the structures ofthese proteins, to understand how a protein’sstructure affects its function, and ultimately todesign drugs that intercede in protein activities(penicillin is a well-known example of a drug thatworks by blocking a protein’s function).Determining protein structure is the key to thedesign and development of effective drugs.

The main purpose in growing protein crystals isto advance our knowledge of biological molecularstructures. Researchers can use microgravity tohelp overcome a significant stumbling block inthe determination of molecular structures: thedifficulty of growing crystals suitable forstructural analysis. Scientists use X-raydiffraction to determine the three-dimensionalmolecular structure of a protein. They cancalculate the location of the atoms that make upthe protein based on the intensity and position ofthe spots formed by the diffracted X-rays. Fromhigh resolution diffraction data, scientists candescribe a protein’s structure on a molecularscale and determine the parts of the protein thatare important to its functions. Using computeranalysis, scientists can create and manipulatethree-dimensional models of the protein andexamine the intricacies of its structure to create adrug that”fits” into a protein’s active site, likeinserting a key into a lock to “turn off” the

Crystallized protein lysozyme after dialysis to remove smallmolecule contaminants.

Page 27: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

19

protein’s function. But X-ray diffraction requireslarge, homogeneous crystals (about the size of agrain of table salt) for analysis. Unfortunately,crystals grown in Earth’s gravity often haveinternal defects that make analysis by X-raydiffraction difficult or impossible. Space Shuttlemissions have shown that crystals of someproteins (and other complex biological moleculessuch as viruses) grown on orbit are larger andhave fewer defects than those grown on Earth.The improved data from the space-grown crystalssignificantly enhance scientists’ understanding ofthe protein’s structure and this information can beused to support structure-based drug design.

Scientists strive for a better understanding of thefundamental mechanisms by which proteins formcrystals. A central goal of microgravity proteincrystal growth experiments is to determine thebasic science that controls how proteins interactand order themselves during the process ofcrystallization. To accomplish this goal, NASA hasbrought together scientists from the proteincrystallography community, traditional crystalgrowers, and other physical scientists to form amultidisciplinary team in order to address theproblems in a comprehensive manner.

Mammalian Cell and Tissue CultureMammalian cell tissue culturing is a major area ofresearch for the biotechnology community. Tissueculturing is one of the basic tools of medicalresearch and is key to developing future medicaltechnologies such as ex vivo (outside of thebody) therapy design and tissue transplantation.To date, medical science has been unable to fullyculture human tissue to the mature states ofdifferentiation found in the body.

The study of normal and cancerous mammaliantissue growth holds enormous promise forapplications in medicine. However, conventionalstatic tissue culture methods form flat sheets ofgrowing cells (due to their settling on the bottomof the container) that differ in appearance andfunction from their three-dimensional counterparts

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

A substance that is homogeneous is uniform in structure and/orcomposition.

Three different types of protein c rystals grown on theSpace Shuttle Columbia in 1995: satellite tobacco mosaicvirus, lysozyme, and thaumatin.

Page 28: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

20

Science Standards

∆ o Life Science∆ o Unifying Concepts and Processes

Differentiation is the process (or the result of that process) bywhich cells and/or tissues undergo a progressive specialization ofform or function.

Mathematics Standards

o Algebrao Conceptual Underpinnings of Calculuso Geometry from an Algebraic Perspective

∆ o Mathematical Connections∆ o Mathematics as Problem Solving

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

The forces acting on a surface can be separated into componentsperpendicular (normal) to and tangential to the surface. Thenormal force causes a normal stress and the tangential force isresponsible for a tangential, or shear, stress acting on the surface.Shear forces cause contiguous parts of a structure or liquid toslide relative to each other.

growing in a living body. In an effort to enhancethreedimensional tissue formation, scientists havedeveloped a ground-based facility for cell andtissue culture called a bioreactor. This instrumentcultures cells in a slowly rotating horizontalcylinder, which produces lower stress levels onthe growing cells than previous Earth-basedexperimental environments. The continuousrotation of the cylinder allows the sample toescape much of the influence of gravity, butbecause the bioreactor environment tends to berather passive, it is sometimes difficult for thegrowing tissue to find the fresh media (foodsupply) it needs to survive.

Another reason normal mammalian cells aresensitive to growth conditions found in standardbioreactors is that fluid flow causes shear forcesthat discourage cell aggregation. This limits boththe development of the tissue and the degree towhich it possesses structures and functionssimilar to those found in the human body. Tissuecultures of the size that can be grown in thesebioreactors allow tests of new treatments oncultures grown from cells from the patient ratherthan on patients themselves. In the future, thistechnology will enable quicker, more thoroughtesting of larger numbers of drugs andtreatments. Ultimately, the bioreactor is expectedto produce even better results when used in amicrogravity environment.

In cooperation with the medical community, thebioreactor design is being used to prepare bettermodels of human colon, prostate, breast, andovarian tumors. Cells grown in conventionalculture systems may not differentiate to form atumor typical of cancer. In the bioreactor,however, these tumors grow into specimens thatresemble the original tumor. Similar results havebeen observed with normal human tissues aswell. Cartilage, bone marrow, heart muscle,skeletal muscle, pancreatic islet cells, liver cells,and kidney cells are examples of the normaltissues currently being grown in rotatingbioreactors by investigators. In addition,

A bioreactor vessel thatflew on the Space Shuttle Discovery inJuly 1995.

Page 29: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

21

laboratory models of heart and kidney diseases,as well as viral infections (including Norwalk virusand Human Immunodeficiency Virus (HIV)) arecurrently being developed using a modified NASAbioreactor experiment design with slightvariations in experimental technique and someadjustments to hardware. Continued use of thebioreactor can improve our knowledge of normaland cancerous tissue development. NASA isbeginning to explore the possibility of culturingtissues in microgravity, where even greaterreduction in stresses on growing tissue samplesmay allow much larger tissue masses to develop.A hioreactor is in use on the Russian SpaceStation Mir in preparation for the InternationalSpace Station.

Fundamental BiotechnologyElectrophoresis has been studied on a dozenSpace Shuttle flights and has led to additionalresearch in fluid physics in the area ofelectrohydrodynamics. Phase partitioningexperiments, which use interfacial energy (theenergy change associated with the contactbetween two different materials) as the means ofseparation, have flown on six missions.

Combustion Science

Combustion, or burning, is a rapid, self-sustaining chemical reaction that releases asignificant amount of heat. Examples of commoncombustion processes are burning candles, forestfires, log fires, the burning of natural gas in homefurnaces, and the burning of gasoline in internalcombustion engines. For combustion to occur,three things must normally be present: a fuel, anoxidizer, and an ignition stimulus. Fuels can besolid, liquid, or gas. Examples of solid fuelsinclude filter paper, wood, and coal. Liquid fuelsinclude gasoline and kerosene. Propane andhydrogen are examples of gaseous fuels.Oxidizers can be solid (such as ammoniumperchlorate, which is used in Space Shuttle boosterrockets), liquid (like hydrogen peroxide), or gaseous

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Sciences in Personal and Social Perspectives∆ o Unifying Concepts and Processes

Electrophoresis is the separation of a substance based on theelectrical charge of the molecule and its motion in an appliedelectric field.

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

An exception to the standard combustion process is hypergoliccombustion. In this situation, a fuel and an oxidizerspontaneously react on contact without the need for an ignitionstimulus. The jets used to maintain and change the Shuttle’sorientation when in orbit are powered by hypergolic reactions.

Page 30: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

22

(like oxygen). Air, which contains oxygen, is aparticularly common oxidizer. An electrical sparkis an example of an ignition stimulus.

Combustion is a key element in many of modernsociety’s critical technologies. Electric powerproduction, home heating, ground transportation,spacecraft and aircraft propulsion, and materialsprocessing are all examples in which combustionis used to convert chemical energy to thermalenergy. Although combustion, which accounts forapproximately 85 percent of the world’s energyusage, is vital to our current way of life, it posesgreat challenges to maintaining a healthyenvironment. Improved understanding ofcombustion will help us deal better with theproblems of pollutants, atmospheric change andglobal warming, unwanted fires and explosions,and the incineration of hazardous wastes. Despitevigorous scientific examination for over a century,researchers still lack full understanding of manyfundamental combustion processes.

Some objectives of microgravity combustionscience research are to enhance ourunderstanding of the fundamental combustionphenomena that are affected by gravity, to useresearch results to advance combustion scienceand technology on Earth, and to address issues offire safety in space. NASA microgravitycombustion science research combines theresults of experiments conducted in ground-based microgravity facilities and orbitinglaboratories and studies how flames ignite,spread, and extinguish (go out) undermicrogravity conditions.

Research in microgravity permits a new range ofcombustion experiments in whichbuoyancyinduced flows and sedimentation arevirtually eliminated. The effects of gravitationalforces often impede combustion studiesperformed on Earth. For example, combustiongenerally produces hot gas (due to the energyreieased in the reaction), which is less dense thatthe cooler gases around it. In Earth’s gravity, the

The familiar shape of a candle flame on Earth iscaused by buoyancy-driven convection. Inmicrogravity, a candle flame assumes a sphericalshape as fresh oxidizer reaches it by diffusionprocesses.

Page 31: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

23

hot gas is pusched up by the denser surroundinggases. As the hot gas rises, it creates buoyancy-induced flow that promotes the mixing of theunburned fuel, oxidizer, and combustionproducts.

The ability to significantly reduce gravity-drivenflows in microgravity helps scientists in severalways. One advantage is that the “quieter” andmore symmetric microgravity environment makesthe experiments easier to model (describemathematically), thus providing a better arenafor testing theories. In addition, eliminatingbuoyancy-induced flows allows scientists to studyphenomena that are obscured by the effects ofgravity, such as the underlying mechanisms offuel and heat transport during combustionprocesses. Because buoyancy effects are nearlyeliminated in microgravity, experiments of longerduration and larger scale are possible, and moredetailed observation and examination ofimportant combustion processes can occur.

Scientists often desire an even mixture of thecomponent parts of fuels so that modelsdeveloped for their experiments can usesimplified sets of equations to represent theprocesses that occur. Sedimentation affectscombustion experiments involving particles ordroplets because, as the components of greaterdensity sink in a gas or liquid, their movementrelative to the other particles creates anasymmetrical flow around the dropping particles.This can complicate the interpretation ofexperimental results. On Earth, scientists mustresort to mechanical supports, levitators, andstirring devices to keep fuels mixed, while fluidsin microgravity stay more evenly mixed withoutsticking together, colliding, or dispersingunevenly.

Mathematics Standards

∆ Computation and Estimationo Discrete Mathematics

∆ o Mathematical Connections∆ o Mathematics as Communication∆ o Mathematics as Problem Solving∆ o Mathematics as Reasoning

Science Standards

∆ o Physical Science∆ o Science as Inquiry∆ o Science and Technology∆ o Unifying Concepas and Processes

The creation and use of mathematical models is a key elementof science, engineering, and technology. Modeling begins withidentifying the physical and chemical phenomena involved in anexperiment. Associated mathematical equations such as equationsof motion are then identified. These governing equations aresolved in order to predict important aspeces of the experimentbehavior, using appropriate values of experiment parameters suchas density, composition, temperature, and pressure. Simplemathematical models can be solved hy hand, while morecomplex experiments are generally modeled using sophisticatedalgorithms on high speed computers.

In microgravity research, scientists use modeling in preparationfor flight experiments and in analysis of the results. Models andexperiment procedures are fine-tuned based on comparisonsbetween model predictions and the results of ground-basedmicrogravity experiments (for example, drop facilities andparabolic aircraft flights). This preliminary work allowsresearchers to best take advantage of space flight opportunities.

Page 32: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

24

To date, combustion science researchers havedemonstrated major differences in the structuresof various types of flames burning undermicrogravity conditions and under 1 g conditions.In addition to the practical implications of theseresults in combustion efficiency, pollutant control,and flammability, these studies establish thatbetter understanding of the individual processesinvolved in the overall combustion process can beobtained by comparing results from microgravityand Earth gravity tests. One clear example of theadvantage of these comparison tests is in the areaof fire safety. Most smoke detectors have beendesigned to detect soot particles in the air, but thesizes of soot particles produced in 1 g aredifferent from those produced in microgravityenvironments. This means that smoke-detectingequipment must be redesigned for use onspacecraft to ensure the safety of equipment andcrew.

Comparisons of research in microgravity and in1 g have also led to improvements in combustiontechnology on Earth that may reduce pollutantsand improve fuel efficiency. Technologicaladvances include a system that measures thecomposition of gas emissions from factorysmoke stacks so that they can be monitored. Inaddition, a monitor for ammonia, which is onegas that poses dangers to air quality, is alreadybeing produced and is available for industrial use.Engineers have also designed a device that allowsnatural gas appliances to operate more efficientlywhile simultaneously reducing air pollution. Thismay be used in home furnaces, industrialprocessing furnaces, and water heaters in thefuture. Another new technology is the use ofadvanced optical diagnostics and lasers to betterdefine the processes of soot formation so thatsoot-control strategies can be developed. Deviceshave also been developed to measure percentagesof soot in exhausts from all types of engines andcombustors, including those in automobiles andairplanes.

Transmission Electron Microscope image of laser-heated soot.

Page 33: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

25

The combustion science program supportsexperiments in the following research areas:

Premixed Gas FlamesIn premixed gas flame research, the fuel andoxidizer gases are completely mixed prior toignition. Scientists are interested in flame speed(the rate at which the flame zone travels awayfrom the ignition source and into the unreactedmixture) as a function of both the type of fuel andoxidizer used and the oxidizer-to-fuel ratio. Withsufficiently high or low ratios, the flame does notmove into the unreacted mixture; these criticalratios are referred to as lower and upperflammability limits and are of considerableinterest in terms of both safety and fundamentalscience. Gravity can strongly affect both flamespeed and flammability limits, chiefly throughbuoyancy effects. Scientists in this area are alsoresearching gravity’s effects on the stability,extinction, structure, and shape of premixed gasflames.

Gaseous Diffusion FlamesIn this area of research, the fuel and oxidizergases are initially separate. They tend to diffuseinto each other and will react at their interfaceupon ignition. The structure of these flames undermicrogravity conditions is quite different than onEarth because of buoyancy-induced flows causedby Earth’s gravity. Scientists study flammabilitylimits, burning rates, and how diffusion flamestructure affects soot formation. Within this area,results of studies of the behavior of gas-jet flamesin a microgravity environment, both in transitionand in turbulent flows, are being used to developmodels with potential applications in creatingeffective strategies to control soot formation inmany practical applications.

Liquid Fuel Droplets and SpraysIn this research area, scientists study thecombustion of individual liquid fuel dropletssuspended in an oxidizing gas (air, for example).For these experiments, investigators commonlyuse fuels

Candle flame energy flow. Adapted from “The Science of Flames”poster, National Energy Foundation, Salt Lake City, Utah.

Page 34: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

26

Ultraviolet images of OH radiation taken at hnIf:vecnndinterval.s during a drrvp tower test of the DropletCombustion Experiment. The diameter of the flame producedby burning a heptane droplet decreases in freefall.

such as heptane, kerosene, and methanol. Gravityhinders fundamental studies of dropletcombustion on Earth due to flows induced byhigh-density droplets that sink andbuoyancyinduced upward acceleration of hotcombustion products relative to the surroundinggas. These flows cause drops to burn unevenly,making it difficult for scientists to drawmeaningful conclusions from their experiments.

This area of study also includes the investigationof the combustion of sprays and ordered arraysof fuel droplets in a microgravity environment foran improved understanding of interactionsbetween individual burning droplets in sprays.Knowledge of spray combustion processesresulting from these studies should lead to majorimprovements in the design of combustors usingliquid fuels.

Fuel Particles and Dust CloudsThis area is particularly important in terms of firesafety because clouds of coal dust have thepotential to cause mine explosions and grain-dustclouds can cause silos and grain elevators toexplode. It is particularly difficult to study thefundamental combustion characteristics of fuel-dust clouds under normal gravity because initiallywelldispersed dust clouds quickly settle due todensity differences between the particles and thesurrounding gas. Because particles stick togetherand collide during the sedimentation process,they form nonuniform fuel-air ratios throughoutthe cloud. In microgravity, fuel-dust cloudsremain evenly mixed, allowing scientists to studythem with much greater experimental control witha goal of mitigating coal mine and grain elevatorhazards.

Flame Spread Along SurfacesAn important factor in fire safety is inhibiting thespread of flames along both solid and liquidsurfaces. Flame spread involves the reactionbetween an oxidizer gas and a condensed-phasefuel or the vapor produced by the “cooking” of

Page 35: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

27

such a fuel. Research has revealed majordifferences in ignition and flame-spreadingcharacteristics of liquid and solid fuels undermicrogravity and normal gravity conditions.Material flammability tests in 1 g, which arestrongly affected by buoyancy-induced flows, donot match results obtained in microgravity. It istherefore useful to study both flame spread andmaterial flammability characteristics inmicrogravity to ensure fire safety in environmentswith various levels of gravity. The knowledgegained from these studies may also lead to betterunderstanding of dangerous combustionreactions on Earth. Microgravity experimentseliminate complexities associated with buoyancyeffects, providing a more fundamental scenariofor the development of flame-spreading theories.

Smoldering CombustionSmoldering combustion is a relatively slow,nonflaming combustion process involving anoxidizer gas and a porous solid fuel. Well-knownexamples of smoldering combustion are“burning” cigarettes and cigars. Smolderingcombustion can also occur on much larger scaleswith fuels such as polyurethane foam. When aporous fuel smolders for a long period of time, itcan create a large volume of gasified fuels, whichare ready to react suddenly if a breeze or someother oxidizer flow occurs. This incites the fuel tomake the transition to full-fledged combustion,often leading to disastrous fires (like thoseinvolving mattresses or sofa cushions). Sinceheat is generated slowly in this process, the rateof combustion is quite sensitive to heat exchange;therefore, buoyancy effects are particularlyimportant. Accordingly, smoldering combustion isexpected to behave quite differently in theabsence of gravity.

Combustion SynthesisCombustion synthesis, a relatively new area ofresearch, involves creating new materials througha combustion process and is closely tied to workin materials science. One area of particularinterest is referred to as self-deflagrating high-

View looking down at a piece qf ashless filter paper with a 1centimeter grid on it. On the USMP-3 Shuttle mission, a radiantheater (two concentric rings exposed at the center of the image)was used to ignite samples to study flame spread and smolderingin weak air f1ows under microgravity conditions. In this image,areas where the grid is not seen have been burned, with thecracking and curling edges of the burning paper leaving a cuspedappearance. The flame started at the heater site and propagatedtoward the right where a fan provided a source of fresh air.Charred paper around the burnt area is a darker grey than theuraffected paper. White areas to the right of the heater rings aresoot zones.

Page 36: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

28

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

A fluid is something that flows. Highly compressible fluids areusually considered gases; essentially incompressible fluids areusually considered liquids. Fluids tend to conform to the shape ofa container. On Earth’s surface, liquids tend to fill the bottom ofan open or closed container and gases tend to fill closedcontainers.

temperature synthesis. This occurs when twomaterials— usually two solids—are mixedtogether, are reactive with one another, and createa reaction that gives off a large amount of heat.Once the reaction is started, the flame willpropagate through a pressed mixture of theseparticles, resulting in a new material. Much of theinitial research in this groundbreaking areainvolves changing variables such as composition,pressure, and preheat temperature. Manipulatingthese factors leads to interesting variations in theproperties of materials created through thesynthesis process.

Flame processes are also being used to createfullerenes and nanoparticles. Fullerenes, a newform of carbon, are expensive to produce at thistime and cannot be produced in large quantities,but scientists predict more uses for them will bedeveloped as they become more readily available.Nanoparticles (super-small particles) are also ofgreat interest to materials scientists due to thechanges in the microstructure of compactedmaterials that can be produced by sintering,which results in improved properties of the finalproducts. These nanoparticles can thus be usedto form better pressed composite materials.

Fluid PhysicsA fluid is any material that flows in response toan applied force; thus, both liquids and gases arefluids. Some arrangements of solids can alsoexhibit fluid-like behaviors; granular systems(such as soil) can respond to forces, like thoseinduced by earthquakes or floods, with a flow-likeshift in the arrangement of solid particles and theair or liquids that fill the spaces between them.Fluid physicists seek to better understand thephysical principles governing fluids, includinghow fluids flow under the influence of energy,such as heat or electricity; how particles and gasbubbles suspended in a fluid interact with andchange the properties of the fluid; how fluidsinteract with solid boundaries; and how fluidschange phase, either from fluid to solid or from onefluid phase to another. Fluid phenomena studied

Page 37: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

29

range in scale from microscopic to atmosphericand include everything from the transport of cellsin the human body to changes in the compositionof the atmosphere.

The universal nature of fluid phenomena makestheir study fundamental to science andengineering. Understanding the fluid-like behaviorof soils under stress will help civil engineersdesign safe buildings in earthquake-prone areas.Materials engineers can benefit from a bettergrasp of how the structure and properties of asolid metal are determined by fluid behaviorduring its formation. And knowledge of the flowcharacteristics of vapor-liquid mixtures is usefulin designing power plants to ensure maximumstability and performance. The work of fluidphysics researchers often applies to the work ofother microgravity scientists.

Complex FluidsThis research area focuses on the uniqueproperties of complex fluids, which includecolloids, gels, magneto-rheological fluids, foams,and granular systems.

Colloids are suspensions of finely divided solidsor liquids in fluids. Some examples of colloidaldispersions are aerosols (liquid droplets in gas),smoke (solid particles in gas), and paint (solid inliquid). Gels are colloidal mixtures of liquids andsolids in which the solids have linked together toform a continuous network, becoming veryviscous (resistant to flow). Magneto-rheologicalfluids consist of suspensions of colloidalparticles. Each particle contains many tiny,randomly oriented magnetic grains and anexternally applied magnetic field can orient themagnetic grains into chains. These chains mayfurther coalesce into larger-scale structures in thesuspension, thereby dramatically increasing theviscosity of the suspension. This increase,however, is totally reversed when the magneticfield is turned off.

Side views of water and airflowing through a clearpipe. At Ig,the air stays on top. In microgravity, the air canform a coredown the center of the pipe.

1 g

µ g

Page 38: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

30

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

Rheology is the scientific study of the deformation and flow ofmatter.

USML-2 Payload Commander Kathryn C. Thomton works at theDrop Physics Module, used to investigate liquid drop behavior inmicrogravity.

A foam is a nonuniform dispersion of gas bubblesin a relatively small volume of liquid that containssurface-active macromolecules, or surfactants(agents that reduce the surface tension ofliquids). Foams have striking properties in thatthey are neither solid, liquid, nor vapor, yet theyexhibit features of all three. Important uses forcustomdesigned foams include detergents,cosmetics, foods, fire extinguishing, oil recovery,and many physical and chemical separationtechniques. Unintentional generation of foam, onthe other hand, is a common problem affectingthe efficiency and speed of a vast number ofindustrial processes involving the mixing oragitation of multicomponent liquids. It alsooccurs in polluted natural waters and in thetreatment of wastewater. In all cases, control offoam rheology and stability is required.

Examples of granular systems include soil andpolystyrene beads, which are often used aspacking material. Granular systems are made upof a series of similar objects that can be as smallas a grain of sand or as large as a boulder.Although granular systems are primarilycomposed of solid particles, their behavior can befluid-like. The strength of a granular system isbased upon the friction between and geometricinterlocking of individual particles, but undercertain forces or stresses, such as those inducedby earthquakes, these systems exhibit fluidicbehavior.

Studying complex fluids in microgravity allowsfor the analysis of fluid phenomena often maskedby the effects of gravity. For example, researchersare particularly interested in the phase transitionsof colloids, such as when a liquid changes to asolid. These transitions are easier to observe inmicrogravity. Foams, which are particularlysensitive to gravity, are more stable (and cantherefore be more closely studied for longerperiods of time) in microgravity. In magneto-rheological fluids, controlling rheology induced bya magnetic field has many potential applications,from shock absorbers and clutch controls for carsto robotic joint controls. Under the force

Page 39: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

31

of Earth’s gravity, the magnetic particles in thesefluids often fall out of suspension due tosedimentation, but in microgravity this problem iseliminated. Investigations of the behavior ofgranular systems, which have previously beenhampered by Earth’s gravity, are more feasible inmicrogravity because they do not settle as theydo on Earth.

Multiphase Flow and Heat TransferThis research area, which has applications in theengineering of heat transfer systems and gaspurification systems, focuses on complexproblems of fluid flow in varying conditions.Scientists are seeking to add to their currentlylimited knowledge of how gravity-dependentprocesses, such as boiling and steamcondensation, occur in microgravity. Boiling isknown to be an efficient way to transfer largeamounts of heat, and as such, it is often used forcooling and for energy conversion systems. Inspace applications, boiling is preferable to othertypes of energy conversion systems because it isefficient and the apparatus needed to generatepower is smaller.

Another of the mechanisms by which energy andmatter move through liquids and gases isdiffusive transport. The way atoms and moleculesdiffuse, or move slowly, through a liquid or gas isdue primarily to differences in concentration ortemperature. Researchers use microgravity tostudy diffusion in complex systems, a processthat would normally be eclipsed by the force ofgravity.

Understanding the physics of multiphase flow andheat transfer will enable scientists to extend therange of human capabilities in space and willenhance the ability of engineers to solve problemson Earth as well. Applications of this researchmay include more effective air conditioning andrefrigeration systems and improvements in powerplants that could reduce the cost of generatingelectricity.

Page 40: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

32

Interfacial PhenomenaResearch in this area focuses on how aninterface, like the boundary between a solid and aliquid, acquires and maintains its shape. Interfacedynamics relate to the interaction of surfaces inresponse to heating, cooling, and chemicalinfluences. A better understanding of this topicwill contribute to improved materials processingand other applications.

Interfacial phenomena, such as the wetting andspreading of two immiscible liquids or thespreading of fluid across a solid surface, areubiquitous in nature and technology. Duckfeathers and waterproof tents repel water becausethe wetting properties of the surfaces of theirfibers prevent water from displacing the air in thegaps between the fibers. In contrast, waterspontaneously displaces air in the gaps of asponge or filter paper. Technologies that rely ondousing surfaces with fluids like agriculturalinsecticides, lubricants, or paints depend on thewetting behavior of liquids and solids. Wetting isalso a dominant factor in materials processingtechniques, including film and spray coating,liquid injection from an orifice, and crystalgrowth. Interfaces dominate the properties andbehavior of advanced composite materials, wherewetting of the constituent materials dictates theprocessing of such materials. Understanding andcontrolling wetting and spreading pose bothscientific and technological challenges.

In reduced gravity, wetting determines theconfiguration and location of fluid interfaces, thusgreatly influencing, if not dominating, thebehavior of multiphase fluid systems. Thisenvironment provides scientists with an excellentopportunity to study wetting and surface tensionforces that are normally masked by the force ofEarth’s gravity. This research also providesinformation that can help improve the design ofspace engineering systems strongly affected bywetting, including liquid-fuel supply tanks, two-phaseheat transfer and/or storage loops, and fluidsmanagement devices for life support purposes.

Comparison of thermocapillary flows on Earth (top) and inmicogravity (bottom). The flow pattern (indicated by the whiteareas) in the Earth-based experiments is only evident on the fluid’ssurface, while the flow pattern in microgravity encompasses theentire fluid.

Page 41: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

33

Dynamics and StabilityThis broad area of research includes dropdynamics, capillarity, and magneto/electro-hydrodynamics.

Drop dynamics research deals with the behaviorof liquid drops and gas bubbles under theinfluence of external forces and chemical effects.Research in drop dynamics ranges from the studyof rain in the atmosphere to the investigation ofchemical processes. A potential application ofthese studies is in the realm of materialsprocessing. In forming solid materials fromliquids in space, it is usually important to createpure and/or uniform solids—gas bubbles anddrops of foreign liquids are undesirable. Yet dueto the microgravity environment, these bubblesand drops of substances of lower densities wouldnot “rise to the top” the way they would if theywere on the ground, which makes extraction ofthe bubbles difficult. Researchers are attemptingto resolve this problem in order to facilitate bettermaterials processing in space.

Scientists are also interested in studying singlebubbles and drops as models for other naturalsystems. The perfect spheres formed by bubblesand drops in microgravity (due to the dominanceof surface tension forces) are an easy fit totheoretical models of behavior—feweradjustments need to be made for the shape of themodel. Investigators can manipulate the sphericaldrops using sound and other impulses, creatingan interactive model for processes such as atomfissioning.

Capillarity refers to a class of effects that dependon surface tension. The shape a liquid assumes ina liquid-liquid or liquid-gas system is controlledby surface tension forces at the interface. Smalldisturbances in the balance of molecular energiesat these boundaries or within the bulk of the liquidcan cause shifts in the liquid’s position and shapewithin a container (such as a fuel tank) or in acontaining material (such as soil). These changes,or capillary effects, often occur in liquids on Earth,

This sequential photo shows a liquid bridge undergoing aseries of shape changes. Liquid bridge investigations on theShuttle have tested theories of electrohydrodynamics.

In materials science research, float 20ne samples aresometimes usedfor crystal growth. For a 87oat-zonesampler the surface tension of the melt keeps the samplesuspended between two sample rods in afurnace. Athorough understanding of the capillarity and surfacetension effects in a molten sample allows betterexperiment control and results prediction.

Page 42: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

34

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

Joule heating occurs when electric current flows through amaterial. This is how an electric toaster works .

Researchers observe thefloat package and data rack of a superfluidhelium experiment on a parabolic aircraft fight.

but are to some degree masked or minimized bythe stronger force of gravity. In microgravity,however, capillary effects become prominent. Thestudy of capillary phenomena in microgravity willenable researchers to better understand andpredict fluid configurational changes both onEarth and in low-gravity environments.

Microgravity fluid physics researchers also studythe effects of magnetic and electric fields on fluidflows, or magneto/electrohydrodynamics.Promising microgravity research subjects in thisarea include weak fluid flows, such as thosefound in poorly conducting fluids in a magneticfield, and Joule heating. In Earth’s gravity, Jouleheating causes buoyancy-driven flows which, inturn, obscure its effects. In microgravity, however,buoyancy-driven flows are nearly eliminated, soresearchers are not only able to study the effectsof Joule heating, but they can also observe otherprocesses involving applied electric fields, suchas electrophoresis.

Fundamental Physics

Physics is a major part of fundamental sciencewhere the ultimate goal is to establish a unifieddescription of the basic laws that govern ourworld. At present fundamental physics includeslow temperature physics, condensed matterphysics (the study of solids and liquids), lasercooling and atomic physics, and gravitational andrelativistic physics. A unifying characteristic ofthese research areas is that they addressfundamental issues which transcend theboundaries of a particular field of science.

The majority of experiments in fundamentalphysics are extensions of investigations inEarthbased laboratories. The microgravityexperiment in these cases presents anopportunity to extend a set of measurementsbeyond what can be done on Earth, often byseveral orders of magnitude. This extension canlead either to a more precise confirmation of ourprevious understanding of a problem,

Page 43: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

35

or it can yield fundamentally new insight ordiscovery. The remainder of fundamental physicsresearch involves tests of the fundamental lawswhich govern our universe. Investigations aim atenhancing our understanding of the most basicaspects of physical laws, and as such may wellhave the most profound and lasting longrangeimpact on mankind’s existence on Earth and inspace.

There are many examples of how fundamentalscience has had an impact on the average person.Basic research in condensed matter physics toexplain the behavior of semiconductors led to thedevelopment of transistors which are now used incommunication devices, and which produce evermore prevalent and capable computer technology.Research in low temperature physics to explorethe properties of fluids at very low temperaturesled to advanced magnetic resonance techniquesthat have brought extremely detailed magneticresonance imaging to the medical doctor, sotoday much exploratory surgery can be avoided.A less widely appreciated part played byfundamental science in today’s world has beenthe need to communicate large quantities of datafrom physics experiments to collaborators atmany locations around the world. Satisfying thisneed was instrumental in the development of theInternet and the World Wide Web.

Fundamental physics research benefits from boththe reduction in gravity’s effects in Earth-orbit andfrom the use of gravity as a variable parameter. Incondensed matter physics, the physics of criticalpoints has been studied under microgravityconditions. This field needs microgravity becausethe ability to approach a critical point in theEarthbound laboratory is limited by the uniformityof the sample which is spoiled by hydrostaticpressure variations. One of the important issuesin condensed matter physics is the nature of theinterface between solids and fluids. The boundaryconditions at this interface have an influence onmacroscopic phenomena, including wetting. Themicroscopic aspects of the system near the

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

The critical point is the temperature at which the differencesbetween liquids and gases disappear. Above that temperature, theliquid smoothly transforms to the gaseous state; boilingdisappears.

Mathematics Standards

∆ o Mathematical Connections∆ o Mathematics as Communication∆ o Mathematics as Problem Solving

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

Hydrostatic pressure is the result of lhe weighl of a materialabove the point of measurement.

Page 44: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

36

Mathematics Standards

∆ o Mathematical Connections∆ o Mathematics as Communication∆ o Mathematics as Problem Solving∆ o Measurement

Science Standards

∆ o History and Nature of Science∆ o Physical Science∆ o Science and Technology∆ o Science as Inquiry∆ o Unifying Concepts and Processes

There are three temperature scales commonly used in the world.The Kelvin scale, the Celsius temperature scale, and theFahrenheit scale. The SI unit for temperature is the Kelvin. Inmost scientific laboratories, temperatures are measured andrecorded in Kelvin’s or degrees Celsius. The Celsius scale is usedfor weather reporting in most of the world. The United States andsome other countries use the Fahrenheit scale for weatherreporting.

The Kelvin scale is defined around the triple point of water (solidice, liquid water, and water vapor coexist in thermal equilibrium)which is assigned the temperature 273.16 K. This is equal to0.01°C and 32.02°F. Absolute zero, the coldest anything can get,is 0 K, -273.15°C, and -459.67°F.

Questions for Discussion• How do you convert between these different temperature

scales?• What are the boiling and freezing points of water on all these

scales, at 1 atm pressure?

boundary are difficult to study. However, when thefluid is near a critical point, the boundary layeradjacent to the solid surface acquires amacroscopic thickness. Research undermicrogravity conditions permits the study of notonly the influence of the boundaries onthermodynamic properties, but also transportproperties such as heat and mass transport. Oneof the most dramatic advancements in atomicphysics over the last decade has been thedemonstration that laser light can be used to coola dilute atomic sample to within micro- or evennano-degrees of absolute zero. At these lowtemperatures, the mean velocity of the atomsdrops from several hundred m/s to cm/s or mm/s, a reduction by four to five orders of magnitude.When atoms are moving this slowly,measurements of atomic properties can be mademore precisely because the atoms stay in a givenpoint in space for a longer time. In this regime,the effects of gravity dominate atomic motion soexperiments performed in a microgravityenvironment would allow even more precisemeasurements.

Among the most important goals of suchresearch is the improvement of ultra-highprecision clocks. These clocks not only providethe standard by which we tell time, but are crucialto the way we communicate and navigate onEarth, in the air, and in space. Laser cooled atomshave significantly improved the accuracy andprecision of clocks because these atoms movevery slowly and they remain in a givenobservation volume for very long times. However,observation times in these clocks are still affectedby gravity. Because of the effects of gravity, theatoms used in these clocks ultimately fall out ofthe observation region due to their own weight.Increased observation times are possible inmicrogravity and can result in furtherimprovements in precision of at least one or twoorders of magnitude.

Indeed, clocks are central to the study of generalrelativity and in questions concerning the verynature of gravity itself. The motivation for space

Page 45: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

37

based clocks is not only tied to the improvedperformance expected in a microgravityenvironment but also these clocks will haveaccess to different positions in space than areavailable on Earth. An important example of thisphysics is revealed in the comparison of an Earth-based clock with a space-based clock. Thiscomparison provides a direct measurement of thegravitational redshift. Tests of Einstein’s theoriesof relativity and of other theories of gravitationserve as a foundation for understanding howmatter and space-time itself behave at largelength scales and under extreme conditions. Thefreefall environment of orbit, the use of lowtemperature techniques, and the use of highprecision frequency standards offer opportunitiesto perform improved tests of these theories.Direct tests of gravitation theories and otherfundamental theories, including the Law ofUniversal Gravitation, can be performed in amicrogravity environment.

Materials ScienceMaterials science is an extremely broad field thatencompasses the study of all materials. Materialsscientists seek to understand the formation,structure, and properties of materials on variousscales, ranging from the atomic to microscopic tomacroscopic (large enough to be visible).Establishing quantitative and predictiverelationships between the way a material isproduced (processing), its structure (how theatoms are arranged), and its properties isfundamental to the study of materials.

Materials exist in two forms: solids and fluids.Solids can be subdivided into two categorie—-crystalline and noncrystalline (amorphous)—based on the internal arrangement of their atomsor molecules. Metals (such as copper, steel andlead), ceramics (such as aluminum oxide andmagnesium oxide), and semiconductors (such assilicon and gallium arsenide) are all crystallinesolids because their atoms form an ordered

Many materials scientists use a triangle such as this todescribe the relationship between structure, processing,and properties. Microgravity can play an important rolein establishing the relationships in a quantitative andpredictive manner.

Page 46: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

38

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

A semiconductor is a substance, such as germanium and silicon,that is a poor electrical conductor at room temperature but isimproved by minute additions of certain substances (dopants) orby the application of heat, light, or voltage; a material with aforbidden energy gap less than 3 eV.

Schematic of the Electromagnetic Containerless Processing Facility(TEMPUS) used on Shuttle missions STS-65 and STS-83.

internal structure. Most polymers (such asplastics) and glasses are amorphous solids,which means that they have no long rangespecifically ordered atomic or moleculararrangement.

One principal objective of microgravity materialsscience research is to gain a better understandingof how gravity-driven phenomena affect thesolidification and crystal growth of materials.Buoyancy-driven convection, sedimentation, andhydrostatic pressure can create defects(irregularities) in the internal structure ofmaterials, which in turn alter their properties.

The virtual absence of gravity-dependentphenomena in microgravity allows researchers tostudy underlying events that are normallyobscured by the effects of gravity and which aretherefore difficult or impossible to studyquantitatively on Earth. For example, inmicrogravity, where buoyancy-driven convectionis greatly reduced, scientists can carefully andquantitatively study segregation, a phenomenonthat influences the distribution of a solid’scomponents as it forms from a liquid or gas.

Microgravity also supports an alternativeapproach to studying materials calledcontainerless processing. Containerlessprocessing has an advantage over normalprocessing in that containers can contaminate thematerials being processed inside them. Inaddition, there are some cases in which there areno containers that will withstand the very hightemperatures and corrosive environments neededto work with certain materials. Containerlessprocessing, in which acoustic, electromagnetic,or electrostatic forces are used to position andmanipulate a sample, thereby eliminating the needfor a container, is an attractive solution to theseproblems.

Furthermore, microgravity requires much smallerforces to control the position of containerlesssamples, so the materials being studied are not

Page 47: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

39

disturbed as much as they would be if they werelevitated on Earth.

Materials science research in microgravity leadsto a better understanding of how materials areformed and how the properties of materials areinfluenced by their formation. Researchers areparticularly interested in increasing theirfundamental knowledge of the physics andchemistry of phase changes (when a materialchanges from liquid to solid, gas to solid, etc.).This knowledge is applied to designing betterprocess-control strategies and productionfacilities in laboratories on Earth. In addition,microgravity experimentation will eventuallyenable the production of limited quantities ofhigh-quality materials and of materials that exhibitunique properties for use as benchmarks.

Microgravity researchers are interested instudying various methods of crystallization,including solidification (like freezing water tomake ice cubes), crystallization from solution (theway rock candy is made from a solution of sugarand water), and crystal growth from the vapor(like frost forming in a freezer). These processesall involve fluids, which are the materials that aremost influenced by gravitational effects.Examining these methods of transforming liquidsor gases into a solid in microgravity givesresearchers insight into other influentialprocesses at work in the crystallization process.

Electronic Materials Electronic materials play an important role in theoperation of computers, medical instruments,power systems, and communications systems.Semiconductors are well-known examples ofelectronic materials and are a main target ofmicrogravity materials science research.Applications include creating crystals for use inX-ray, gamma-ray, and infrared detectors, lasers,computer chips, and solar cells. Each of thesedevices epends on the ability to manipulate thecrystalline and chemical structure (perfection) of

Schematic diagram of a multizone furnace used to growsemiconductor materials on the Shuttle. A mechanism moves anexisting c crystal through the temperature zones, melting thesample then cooling it so that it solidifies. In other furnacedesigns, the heating mechanism moves and the sample isstationary. What are the advantages and disadvantages of eachapproach?

Page 48: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

40

Mathematics Standards

∆ o Mathematical Connections∆ Patterns and Functions∆ Geometry

o Geometry from a Synthetic Perspective

Science Standards

∆ o Earth and Space Science∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

Questions for Discussion• What is an ordinary drinking glass made from?• What different things are added to glass to change its

properties?• What natural processes produce glasses?• What are the differences between how glasses and crystalline

solids fracture?

the material, which can be strongly influenced bygravity as crystals are formed.

The properties of electronic materials are directlyrelated to the degree of chemical and crystallineperfection present in the materials. However,perfect crystals are not normally the ultimategoal. For example, the presence of just a fewimpurities in some electronic materials canchange their ability to conduct electricity by overa million times. By carefully controlling crystallinedefects and the introduction of desirableimpurities to the crystals, scientists andengineers can design better electronic deviceswith a wide range of applications.

Glasses and CeramicsA glass is any material that is formed without along range ordered arrangement of atoms. Somematerials that usually take crystalline forms, likemetals, can also be forced to form as glasses byrapidly cooling molten materials to a temperaturefar below their normal solidification point. Whenthe material solidifies, it freezes so quickly that itsatoms or molecules do not have time to arrangethemselves systematically.

Ceramics are inorganic nonmetallic materials thatcan be extraordinarily strong at very hightemperatures, performing far better than metallicsystems under certain circumstances. They willhave many more applications when importantfundamental problems can be solved. If a ceramicturbine blade, for example, could operate at hightemperatures while maintaining its strength, itwould provide overall thermodynamic efficienciesand fuel efficiencies that would revolutionizetransportation. The problem with ceramics is thatwhen they fail, they fail catastrophically, breakingin an irreparable manner.

Glasses and ceramics are generally unable toabsorb the impacts that metals can; instead, theycrack under great force or stress (whereas metalsgenerally bend before they break). An importantpart of ceramics and glass research in

Schematic of silicon dioxide tetrahedra. The topview is of a crystalline ordered structure. Thebottom view is of a disordered glassy solid.

Page 49: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

41

microgravity involves controlling the minute flawsthat govern how these materials fail. Frominformation obtained through microgravityresearch, scientists hope to be able to control theprocessing of ceramics so that they can, duringprocessing, prevent the formation ofimperfections that lead to catastrophic failure.

Applications for knowledge obtained throughresearch in these areas include improving glassfibers used in telecommunications and creatinghigh-strength, abrasion-resistant crystallineceramics used for gas turbines, fuel-efficientinternal combustion engines, and bioceramicartificial bones, joints, and teeth.

Metals and AlloysMetals and alloys constitute an importantcategory of engineered materials. These materialsinclude structural materials, many types ofcomposites, electrical conductors, and magneticmaterials. Research in this area is primarilyconcerned with advancing the understanding ofmetals and alloys processing so that structureand, ultimately, properties, can be controlled asthe materials are originally formed. By removingthe influence of gravity, scientists can moreclosely observe influential processes in structureformation that occurs during solidification. Theproperties of metals and alloys are linked to theircrystalline and chemical structure; for example,the mechanical strength and corrosion resistanceof an alloy are determined by its internalarrangement of atoms, which develops as themetal or alloy solidifies from its molten state.

One aspect of the solidification of metals andalloys that influences their microstructures is theshape of the boundary, or interface, that existsbetween a liquid and a solid in a solidifyingmaterial. During the solidification process, as therate of solidification increases under the samethermal conditions, the shape of the solidifyinginterface has been shown to go through a seriesof transitions. At low rates of growths theinterface is planar (flat or smoothly curved

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Unifying Concepts and Processes

An alloy is a combination of two or more metals.

Magnification of a sample of an aluminum-indium alloy. Whenthe sample is melted then controllably solidifies in the AGHF; theindium forms in cylindrica lfibers within a solid aluminummatrix.

Page 50: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

42

Mathematics Standards

∆ Geometryo Geometry from an Algebraic Perspectiveo Geometry from a Synthetic Perspective

∆ o Mathematical Connections∆ o Mathematics as Communication

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

One of the important characteristics of a solid is its shape. On avisible scale, the function of some solids may depend on theability to sit in a stable manner on a surface or to fit tightly intosome configuration. On a smaller scale, the structures ofcrystalline solids are defined by the ordered placement of atoms.The basis of understanding crystalline structure and the shapes ofsolids is a knowledge of the definitions of two-dimensionalshapes (polygons) and three-dimensional solids (polyhedra).

A simple k-sided polygon is defined by connecting k points in aplane with line segments such that no edges intersect except atthe defining points (vertices). The sum of the angles in anypolygon equals 2x(k-2)x90°. Specific names given to somesimple polygons are given below.

Name # of Sides (k)triangle 3quadrilateral 4pentagon 5hexagon 6heptagon 7octagon 8nonagon 9decagon 10undecagon 11dodecagon 12

Regular polygons are those for which all the sides are the samelength and all the angles are the same. The angles of a regularpolygon are defined by θ=(k-2)x 180°/k.

Questions for Discussion• Discuss special cases of triangles and quadrilaterals such as

isosceles triangles, parallelograms, trapezoids.• What is the common name for a regular triangle? For a regular

quadrilateral?• Is there a general equation for the area of any polygon’?

on a macroscopic scale). As the rate of growthincreases, the interface develops a corrugatedtexture until three dimensional cells (similar inshape to the cells in a beehive but much smaller)form in the solid. A further increase in the rate ofgrowth causes the formation of dendrites. Thedevelopment of these different interface shapesand the transition from one shape to another iscontrolled by the morphological stability (shapestability) of the interface. This stability isinfluenced by many factors. Gravity plays animportant role in a number of them. In particular,buoyancy-driven convection can influence thestability and, thus, the shape of the solidifyinginterface. Data obtained about the conditionsunder which certain types of solidificationboundaries appear can help to explain theformation of the crystalline structure of amaterial.

Another area of interest in metals and alloysresearch in microgravity is multiphasesolidification. Certain materials, which are knownas eutectics and monotectics, transform from asingle phase liquid to substances of more thanone phase when they are solidified. When thesematerials are processed on Earth, the resultantsubstances have a structure that was influencedby gravity either due to buoyancy-drivenconvection or sedimentation. But when processedin microgravity, theory predicts that the endproduct should consist of an evenly dispersed,multiphase structure.

Eutectic solidification is when one liquid, ofuniform composition, forms with two distinctsolid phases. An example of such a material is thealloy manganese-bismuth. Solidifying liquid Mn-Bi results in two different solids, each of whichhas a chemical composition that differs from theliquid. One solid (the minor phase) is distributedas rods, particles, or layers throughout the othersolid (a continuous matrix, or major phase).

Monotectics are similar to eutectics, except that amonotectic liquid solidifies to form a solid and a

Page 51: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

43

liquid (both of which are different in compositionfrom the original liquid). Al-In is a monotectic thatstarts out as indium dissolved completely inaluminum, but when the alloy is solidified underthe appropriate conditions, it forms a solidaluminum matrix with long thin “rods” of liquidindium inside it. As the system cools, the rods ofliquid indium freeze into solid rods. The indiumrods are dispersed within the structure of thesolidified material.

PolymersPolymers are macromolecules (very largemolecules) made up of numerous small repeatingmolecular units called monomers. They appearnaturally in wool, silk, and rubber and aremanufactured as acrylic, nylon, polyester, andplastic. Polymers are typically composed of longchains of monomers, appearing on the molecularscale as if they had a spine of particular elementssuch as carbon and nitrogen. The bondingbetween individual polymer molecules affects thematerial’s physical properties such as surfacetension, miscibility, and solubility. Manipulation ofthese bonds under microgravity conditions maylead to the development of processes to producepolymers with more uniform and controlledspecific properties. Important optoelectronic andphotonic applications are emerging for polymers,and many of the properties needed are affected bythe polymers’ crystallinity. This crystallinity,which is the extent to which chains of moleculesline up with each other when the polymer isformed, may be more easily understood andcontrolled when removed from the influence ofgravity.

Growing polymer crystals is more difficult thangrowing inorganic crystals (such as metals andalloys) because the individual polymer moleculesweigh more and are more structurally complex,which hinders their ability to attach to a growingcrystal in the correct position. Yet in microgravity,the process of polymer crystal growth can bestudied in a fundamental way, with specialattention to the effects of such variables as

Regular polyhedra (or the Platonic Solids) are listed and shownbelow.

Name Formed Bytetrahedron 4 trianglescube 6 squaresoctahedron 8 trianglesdodecahedron 12 pentagonsicosahedron 20 triangles

The Five Regular Polyhedra or Platonic Solids Tnp-Tetrahedron;second row left-Cube: second row right- Octahedron; third rowleft-Dodecahedron; third row right-Icosahedron.

Questions for Discussion• What do you think of as a cylinder and cone?• What are the general definitions cylinder and cone’?• What shapes are some mineral samples you have in your

classroom?• Investigate the crystalline structure of halite (rock salt),

fluorine, quartz, diamond, iron.

Page 52: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

44

NASA’s Enterprise for the HumanExploration and Development of Space

The goals of this Enterprise are to• Increase human knowledge of nature’s processes using the

space environment,• Explore and settle the Solar System,• Achieve routine space travel,• Enrich life on Earth through people living and working in

space.

Microgravity research will contribute to the areas of cryogenicfuel management, spacecraft systems, in-situ resource utilization,power generation and storage, life support, fire safety, spacestructures, and science exploration.

Elemental Percent Weight on Earth and Moon

Earth’s Crust Lunar HighlandSoils

O 47 45 Fe 5 5

Si 28 21Mg 2 4Ca 4 11Al 8 13Na 3 0K 3 0

temperature, compositional gradients, and thesize of individual polymer units on crystal growth.In addition, just as microgravity enables thegrowth of larger protein crystals, it may allowresearchers to grow single, large polymer crystalsfor use in studying properties of polymers anddetermining the effects of crystal defects on thoseproperties.

Microgravity Research andExploration

There is one endeavor for which microgravityresearch is essential. That is the goal of exploringnew frontiers of space and using the Moon andMars as stepping stones on our journey. Toachieve these goals, we must design effective lifesupport systems, habitation structures, andtransportation vehicles. To come up withworkable designs, we must have a thoroughunderstanding of how the liquids and gases thatwe need to sustain human, plant, and animal lifecan be obtained, transported, and maintained; ofhow structural materials can be formed in-situ(on site); and of what types of fuels and fueldelivery systems would allow us to get aroundmost efficiently. Microgravity research canprovide the insight needed to get us on our way.

The ability to use extraterrestrial resources is akey element in the exploration of the solarsystem. We believe that we can use the Moon asa research base to develop and improveprocesses for obtaining gases and water forhuman life support and plant growth; for creatingbuilding materials; and for producing propellantsand other products for transportation and powergeneration. Oxygen extracted from lunar rocksand soils will be used for life support and liquidoxygen fuel. A byproduct of the extraction ofoxygen from lunar minerals may be metals andsemiconductors such as magnesium, iron, andsilicon. Metals produced on the Moon andmaterial mined from the surface will then be usedfor construction of habitats, successiveprocessing plants, and solar cells.

Page 53: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

45

Current research in the areas of microgravityscience will guide our path as we develop themeans to use the Moon as a stepping stone toMars. Research into how granular materialsbehave under reduced gravity conditions will beimportant when we design equipment to mine andmove large amounts of lunar material. The abilityto extract gases and metals from mineralsrequires an understanding of how gases, liquids,and solids of different densities interact in lunargravity. Building blocks for habitats and otherstructures can be made from the lunar regolith.Research into sedimentation and sintering underreduced gravity conditions will lead to appropriatemanufacturing procedures. Experiments havealready been performed on the Space Shuttle todetermine how concrete and mortar mixes andcures in microgravity. An understanding of fluidflow and combustion processes is vital for all thematerials and gas production facilities that will beused on the Moon and beyond.

Science Standards

∆ o Earth and Space Science∆ o Physical Science

Regolith is a layer of powder-like dust and loose rock that restson bedrock. In the case of the moon, fragmentation of surfacerocks by meteorite bombardment created much of the regolithmaterial.

Page 54: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

46

Skylab, America’s first space station.

MicrogravityScience SpaceFlights

Until the mid-20th century, gravity was anunavoidable aspect of research and technology.During the latter half of the century, the use ofdrop towers to reduce the effects of gravitybecame more prevalent, although the extremelyshort periods of time they provided (<6 seconds)severely restricted the type of research that couldbe performed.

Initial microgravity research centered aroundsolving space flight problems created by thereduction in gravity’s effects experienced on orbit.How do you get the proper amount of fuel to arocket engine in space or water to an astronaut ona spacewalk? The brief periods of microgravityavailable in drop towers at the Lewis ResearchCenter and the Marshall Space Flight Center weresufficient to answer these basic questions and todevelop the pressurized systems and other newtechnologies needed to cope with this newenvironment. But, they still were not sufficient toinvestigate the host of other questions that wereraised by having gravity as an experimentalvariable.

The first long-term opportunities to exploremicrogravity and conduct research relatively freeof the effects of gravity came during the latterstages of NASA’s first great era of discovery. TheApollo program presented scientists with thechance to test ideas for using the spaceenvironment for research in materials, fluid, andlife sciences. The current NASA microgravityprogram had its beginning in experimentsconducted in the later flights of Apollo, theApollo-Soyuz Test Project, and onboard Skylab,America’s first space station.

Page 55: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

47

Preliminary microgravity experiments conductedduring the 1970’s were severely constrained,either by the relatively low power levels and spaceavailable on the Apollo spacecraft, or by the lownumber of flight opportunities provided to Skylab.These experiments, as simple as they were,provided new insights into the roles of fluid andheat flows in materials processing Much of ourunderstanding of the physics underlyingsemiconductor crystal growth, for example, canbe traced back to research initiated on Skylab.

Since the early 1980’s, NASA has sent crews andpayloads into orbit on board the Space Shuttle.The Space Shuttle has given microgravityscientists an opportunity to bring theirexperiments to low-Earth orbit on a more regularbasis. The Shuttle introduced significant newcapabilities for microgravity research: larger,scientifically trained crews; a major increase inpayload volume and mass and available power;and the return to Earth of all instruments,samples, and data. The Spacelab module,developed for the Shuttle by the European SpaceAgency, gives researchers a laboratory withenough power and volume to conduct a limitedrange of sophisticated microgravity experimentsin space.

Use of the Shuttle for microgravity researchbegan in 1982, on its third flight, and continuestoday on many missions. In fact, most Shuttlemissions that aren’t dedicated to microgravityresearch do carry microgravity experiments assecondary payloads.

The Spacelab-1 mission was launched inNovember 1983. The primary purpose of themission was to test the operations of the complexSpacelab and its subsystems. The 71microgravity experiments, conducted usinginstruments from the European Space Agency,produced many interesting and provocativeresults. One investigator used the travelling heatermethod to grow a crystal of gallium antimonidedoped with tellurium (a compound useful for

The Spacelab module in the Orbiter Cargo Bay.

Page 56: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

48

making electronic devices). Due to the absence ofgravity-driven convection, the space-growncrystal had a far more uniform distribution oftellurium than could be achieved on Earth. Asecond investigator used molten tin to studydiffusion in low gravity- research that canimprove our understanding of the solidification ofmolten metals.

Another Shuttle mission using the Spacelabmodule was Spacelab-3, which flew in April 1985.SL-3 was the first mission to include U.S.developed microgravity research instruments inthe Spacelab. One of these instruments supportedan experiment to study the growth of crystals ofmercury iodide-a material of significant interestfor use as a sensitive detector of X-rays andgamma rays. Grown at a high rate for a relativelyshort time, the resulting crystal was as good asthe best crystal grown in the Earth-basedlaboratory. Another U.S. experiment consisted ofa series of tests on fluid behavior using aspherical test cell. The microgravity environmentallowed the researcher to use the test cell tomimic the behavior of the atmosphere over alarge part of Earth’s surface. Results from thisexperiment were used to improve mathematicalmodels of our atmosphere.

In October 1985, NASA launched a Spacelabmission sponsored by the Federal Republic ofGermany, designated Spacelab-D1. American andGerman scientists conducted experiments tosynthesize high quality semiconductor crystalsuseful in infrared detectors and lasers. Thesecrystals had improved properties and were moreuniform in composition than their Earth-growncounterparts. Researchers also successfullymeasured critical properties of molten alloys.

The first Spacelab mission dedicated to United States microgravityscience on USML-I. The coast of Florida appears in the background.

Page 57: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

49

International MicrogravityLaboratory-1, January 1992More than 220 scientists from the United Statesand 14 other countries contributed to theexperiments flown on the first InternationalMicrogravity Laboratory (IML-1) in January 1992.Several biotechnology experiments concernedwith protein crystal growth enabled NASAscientists to successfully test and compare twodifferent crystal-growing devices.

A German device called the Cryostat producedsuperior-quality crystals of proteins from severalmicroorganisms including the satellite tobaccomosaic virus (STMV), which has roles in diseasesaffecting more than 150 crop plants. As a resultof this experiment, scientists now have a muchclearer understanding of the overall structure ofSTMV. This information is useful in efforts todevelop strategies for combating viral damage tocrops.

IML-1 also carried experiments designed to probehow microgravity affects the internal structure ofmetal alloys as they solidify. The growthcharacteristics, determined from one of theexperiments, matched the predictions of existingmodels, providing experimental evidence thatcurrent hypotheses about alloy formation arecorrect.

United States MicrogravityLaboratory-1, June 1992In June 1992 the first United States MicrogravityLaboratory (USML-1) flew aboard a 14-dayshuttle mission, the longest up to that time. ThisSpacelab-based mission was an important step ina long-term commitment to build a microgravityprogram involving government, academic, andindustrial researchers.

The payload included 31 microgravityexperiments using some facilities andinstruments from previous flights, including theProtein Crystal Growth facility, a Space

Payload Commander Bonnie J. Dunbar and Payload SpecialistLawrence J. DeLucas working in the module on USML-1.

Page 58: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

50

Science Standards

∆ o Earth and Space Science∆ o History and Nature Of Science∆ o Physical Science∆ o Unifying Concepts and Processes

Questions for Discussion• What are Cd, Hg, Te, Zn?• What do these elements have in common?Hint: Look at their position on the periodic table of the elements.

Acceleration Measurement System, and the SolidSurface Combustion Experiment. New experimentfacilities, all designed to be reusable on futuremissions, included the Crystal Growth Furnace(CGF), a Glovebox provided by the EuropeanSpace Agency, the Surface Tension DrivenConvection Experiment apparatus (STDCE), andthe Drop Physics Module.

Investigators used the CGF to grow crystals offour different semiconductor materials attemperatures as high as 1260°C. One space-grown CdZnTe crystal developed far fewerimperfections than even the best Earth-growncrystals, results that far exceeded pre-flightexpectations. Thin crystals of HgCdTe grown fromthe vapor phase had mirror-smooth surfaces evenat high magnifications. This type of surface wasnot observed on Earth-grown crystals.

Researchers used the STDCE apparatus to explorehow internal movements of a liquid are createdwhen there are spatial differences in temperatureon the liquid’s surface. The results are in closeagreement with advanced theories and modelsthat the experiment researchers developed.

In the Drop Physics Module, sound waves wereused to position and manipulate liquid droplets.Surface tension controlled the shape of thedroplets in ways that confirmed theoreticalpredictions. The dynamics of rotating drops ofsilicone oil also conformed to theoreticalpredictions. Experimental and theoretical resultsof this kind are significant because they illustratean important part of the scientific method:hypotheses are formed and carefully plannedexperiments are conducted to test them.

Sixteen different investigations run by NASAresearchers used the Glovebox, which provided asafe enclosed working area; it also was equippedwith photographic equipment to provide a visualrecord of investigation operations. The Gloveboxallowed crew members to perform proteincrystallization studies as they would on Earth,including procedures that require

Fission sequence of a rotating levitated drop.

Page 59: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

51

hands-on manipulation. Among other results, useof the Glovebox provided the best-ever crystals ofmalic enzyme that may be useful in developinganti-parasitic drugs.

The burning of small candles in the Gloveboxprovided new insights into how flames can existin an environment in which there is no air flow.The results were similar (though much longerlived) to what can be seen by conducting similarexperiments in freefall here on Earth. (See CandleFlames in Microgravity, in the Activities section ofthis guide.) The candles burned for about 45 to60 seconds in the Glovebox experiments.

Another Glovebox investigation tested how wireinsulation burns under different conditions,including in perfectly still air (no air flow) and inair flowing through the chamber from differentdirections. This research has yielded extremelyimportant fundamental information and also haspractical applications, including methods forfurther increasing fire safety aboard spacecraft.

The crew of scientist astronauts in the Spacelabplayed an important role in maximizing thescience return from this mission. For instance,they attached a flexible type of glovebox, whichprovided an extra level of safety, to the CrystalGrowth Furnace. The furnace was then opened,previously processed samples were removed andan additional sample was inserted. This enabledanother three experiments to be conducted. Twoother unprocessed samples were already in thefurnace.

Spacelab-J,September 1992The Spacelab-J (SL-J) mission flew in September1992. SL-J was the first Space Shuttle missionshared by NASA and Japan’s National SpaceDevelopment Agency (NASDA). NASAmicrogravity experiments focused on proteincrystal growth and collecting acceleration data insupport of the microgravity experiments.

Zeolite crystals can be grown in the Glovebox Facility. Shownhere are photos (at the same scale) of zeolite crystals grown onUSML-I (top) and on Earth (bottom).

Page 60: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

52

NASDA’s science payload consisted of 22experiments focused on materials science andthe behavior of fluids, and 12 human biologyexperiments. NASDA also contributed twoexperiment facilities. One of these, the LargeIsothermal Furnace, was used to explore howvarious aspects of processing affect thestructure and properties of materials. Thesecond apparatus was a Free-FlowElectrophoresis Unit used to separate differenttypes of molecules in a fluid.

United States MicrogravityPayload-1, October 1992The first United States Microgravity Payload(USMP-1) flew on a 10-day Space Shuttlemission launched on October 22, 1992. Themission was the first in an ongoing effort thatemploys telescience to conduct experiments ona carrier in the Space Shuttle Cargo Bay.Telescience refers to how microgravityexperiments can be conducted by scientists onthe ground using remote control.

The carrier in the Cargo Bay consisted of twoMission Peculiar Equipment Support Structures.On-board, the two Space AccelerationMeasurement Systems measured how crewmovements, equipment operation, and thrusterfirings affected the microgravity environmentduring the experiments. This information wasrelayed to scientists on the ground, who thencorrelated it with incoming experiment data.

A high point of USMP-1 was the first flight ofMEPHISTO, a multi-mission collaborationbetween NASA-supported scientists and Frenchresearchers. MEPHISTO (designed and built bythe French Space Agency, Centre Nationald’Etudes Spatiales or CNES) is designed to studythe solidification process of molten metals andother substances. Three identical samples of onealloy (a combination of tin and bismuth) weresolidified, melted, and resolidified more than 40times, under slightly different conditions eachtime. As each cycle ended, data were transmitted

USMP experiments are mounted on Mission PeculiarEquipment Support Structures in the Shuttle Cay.rgo Bay.

Page 61: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

53

from the Space Shuttle to Marshall Space FlightCenter. There, researchers analyzed theinformation in combination with data from theSpace Acceleration Measurement System andsent back commands for adjustments. In all, theinvestigators relayed more than 5000 commandsdirectly to their instruments on orbit. Researcherscompared experiment data with the predictions oftheoretical models and showed that mathematicalmodels can predict important aspects of theexperiment behavior. This first MEPHISTO effortproved that telescience projects can be carriedout efficiently, with successful results.

The lambda point for liquid helium is thecombination of temperature and pressure atwhich normal liquid helium changes to asuperfluid. On Earth, effects of gravity make itvirtually impossible to measure properties ofsubstances very close to this point. On USMP-1,the Lambda Point Experiment cooled liquidhelium to an extremely low temperature—-a littlemore than 2 K above absolute zero. Investigatorsmeasured changes in its properties immediatelybefore it changed from a normal fluid to asuperfluid. Performing the test in microgravityyielded temperature measurements accurate towithin a fraction of one billionth of a degree—several hundred times more accurate than wouldhave been possible in normal gravity. Overall thenew data were five times more accurate than inany previous experiment.

United States MicrogravityPayload-2, March 1994The second United States Microgravity Payload(USMP-2) flew aboard the Space ShuttleColumbia for 14 days from March 4 to March 18,1994. Building on the success of telescience inUSMP-1, the Shuttle Cargo Bay carried fourprimary experiments which were controlled byapproximately 10,000 commands relayed byscientists at Marshall Space Flight Center. USMP-2 also included two Space AccelerationMeasurement Systems, which provided scientists

Science and mission management teams monitor and controlexperiments from operations centers worldwide.

Page 62: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

54

Science Standards

∆ o Physical Science∆ o Unifying Concepts and Processes

Dendrites are branching structures that develop as a moltenmetal solidifies under certain conditions. The root of this word isthe (Greek dendron, meaning tree. Branching structures inbiology (nerve cells) and geology (drainage systems) are alsoreferred to as being dendritic.

on the ground with nearly instant feedback onhow various kinds of motion-including crewexercise and vibrations from thruster engines-affected mission experiments. The OrbitalAcceleration Research Experiment in the CargoBay collected supplemental data on acceleration,providing an indication of the quasi-steadyacceleration levels experienced by theexperiments.

Throughout the mission, the Critical Fluid LightScattering Experiment—-nicknamed Zeno—analyzed the behavior of the element xenon as itfluctuated between two different states, liquid andgas. First, a chamber containing liquid xenon washeated. Then, laser beams were passed throughthe chamber as the xenon reached temperaturesnear this transition point. A series ofmeasurements were taken of how the laser beamswere scattered (deflected) as the xenon shiftedfrom one state to another. Researchers expectedthat performing the experiment on orbit wouldprovide more detailed information about how asubstance changes phase than could be obtainedon Earth. In fact, the results producedobservations more than 100 times more precisethan the best measurement on the ground.

The Isothermal Dendritic Growth Experiment(IDGE) examined the solidification of a materialthat is a well-established model for metals. Thismaterial is especially useful as a model because itis transparent, so a camera can actually recordwhat happens inside a sample as it freezes. In 59experiments conducted during 9 days, over 100television images of growing dendrites were sentto the ground and examined by the researchteam. Dendritic growth velocities and tip radii ofcurvature were measured. Results obtained undercertain experiment conditions were not consistentwith current theory. This inconsistency was thesubject of subsequent research on USMP-3. Inanother successful demonstration of telescience,the team relayed more than 200 commands to theIDGE, fine-tuning its operations.

A dendrite grown in the Isothermal Dendritic GrowthExperiment aboard the USMP-2. This is an example of howmost metals solidify.

Page 63: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

55

USMP-2 also included a MEPHISTO experiment.On this mission, the MEPHISTO apparatus wasused for U.S. experiments to test how gravityaffects the formation of crystals from an alloy ofbismuth and tin that behaves much like asemiconductor during crystal growth.Metallurgical analysis of the samples has shownthat interactions between the molten and solidalloy during crystallization play a key role incontrolling the final morphological stability of thealloy.

Another USMP-2 materials science experimentused the Advanced Automated DirectionalSolidification Furnace (AADSF). An eleven dayexperiment using the AADSF yielded a large, well-controlled sample of the alloy semiconductor,HgCdTe. The results of various analysistechniques performed on the crystal indicate thatvariations in the acceleration environment had amarked effect (due to changing residual fluidflow) on the final distribution of the alloy’scomponents in the crystal.

International MicrogravityLaboratory-2, July 1994The second International Microgravity Laboratory(IML-2), with a payload of 82 major experiments,flew in July 1994 on the longest Space Shuttleflight to that time. IML-2 truly was a world classventure, representing the work of scientists fromthe U.S. and 12 other countries.

Materials science experiments focused on varioustypes of metals processing. One was sintering, aprocess that can combine different metals byapplying heat and pressure to them. A series ofthree sintering experiments expanded the use inspace of the Japanese built Large IsothermalFurnace, first flown on SL-J. It successfullysintered alloys of nickel, iron, and tungsten.

Other experiments explored the capabilities of aGerman-built facility called TEMPUS. It wasdesigned to position molten metal experiment

Representations of different .shapes of the liquid-solid interface in asolidifying material: a) planar, b) cellular; and c) dendritic. Moreinformation about interface morphology is provided in the Metalsand Alloys discussion in the Materials Science section of thispublication.

a

b

c

Page 64: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

56

Mathematics Standards

o Conceptual Underpinnings of Calculuso Functions

∆ o Mathematical Connections∆ Patterns and Functions

Science Standards

∆ o Earth and Space Science∆ o Physical Science∆ o Science and Technology∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

A gradient is the variation of a quantity such as temperature,pressure, or concentration with respect to a given parameter,typically distance. A temperature gradient can have dimensionsof temperature per length, for example, °C/cm.

samples (molten drops) away from the surfacesof a container in order to eliminate processingside effects of containers. Experiments of fourU.S. scientists were successfully completed, andthe research team developed improvedprocedures for managing multi-user facilities.

One of the experiments used a clever approach tomeasure two important thermophysical propertiesof molten metals. While a spherical drop ofmolten metal was positioned in a containerlessmanner it was momentarily distorted by usingelectromagnetic forces to squeeze it. When thesqueezing was released, the droplet began tooscillate. The surface tension of the molten metalwas determined from the frequency of theoscillation. The oscillation gradually decayed. Therate at which the decay occurred was used todetermine the viscosity of the molten material.

Biotechnology experiments were performed usingthe Advanced Protein Crystallization Facility,developed by the European Space Agency. Thefacility’s 48 growth chambers operatedunattended throughout the flight, producing high-quality crystals of nine proteins. High-resolutionvideo cameras monitored critical crystal growthexperiments, providing the research team with avisual record of the processes. U.S. investigatorsused the Bubble, Drop, and Particle Unit to studyhow temperature gradients in the liquidsinfluence the movement and shape of gas bubblesand liquid drops. The Critical Point Facilityenabled researchers to study how a fluid behavesat its critical point. Research using the CriticalPoint Facility is applicable to a broad range ofscientific questions, including how variouscharacteristics of solids change under differentexperimental conditions.

Page 65: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

57

Force ofEarth'sGravity

Earth Environment

ExperimentalSphere

Microgravity Environment

Force ofRadialGravityExperimental

Sphere

Gravitational force acting on spherical planetarymodels on Earth and in a microgravity environment

United States MicrogravityLaboratory-2, October 1995The second United States MicrogravityLaboratory (USML-2) launched on October 20,1995 for a mission with more than 16 days onorbit. During that time microgravity research wasconducted around-the-clock in the areas ofbiotechnology, combustion science, fluid physics,and materials science. It was a perfect example ofinteractive science in a unique laboratoryenvironment.

Along with investigations that previously flew onUSML-1, several additional experiment facilitiesflew on USML-2. Fourteen protein crystal growthexperiments in the Advanced ProteinCrystallization Facility had varied results thatprovided more insight into the structures of someof the proteins and into optimal experimentconditions. The goal of the Geophysical Fluid FlowCell experiment was to study how fluids move inmicrogravity as a means of understanding fluidflow in oceans, atmospheres, planets, and stars.The results of the studies of fluid movement andvelocity are still being analyzed.

Four separate studies were performed in theCrystal Growth Furnace (CGF). The goals of theexperiments were to investigate quantitatively thegravitational influences on the growth and qualityof the compound semiconductor, CdZnTe, usingthe seeded, modified Bridgman-Stockbargercrystal growth technique; to investigatetechniques for uniformly distributing a dopant,selenium, during the growth of GaAs crystals; tounderstand the initial phase of the process ofvapor crystal growth of complex, alloy-typesemiconductors (HgCdTe); and to test theintegration of a current induced interfacedemarcation capability into the CGF system and toassess the influences of a change in Shuttleattitude on a steady-state growth system usingthe demonstrated capabilities of the interfacedemarcation technique.

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

A dopant is an impurity intentionally added to a puresemiconductor to alter its electronic or optical properties.

Earth Environment Microgravity Environment

Force ofEarth’sGravity

ExperimentalSphere

Force ofRadialGravity

ExperimentalSphere

Gravitational force acting on spherical planetarymodels on Earth and in a microgravity environment

In the Geophysical Fluid Flow Cell, electric charges,electrostatic force, and heaters are used to simulatebuoyancy forces, radial gravity, and heating patternsin planetary atmospheres. As shown in the diagram,attempts to use spherical models on Earth arehampered by the force of Earth’s gravity actingperpendicular to the sphere’s rotation (indicated bythe large curving arrow around the sphere’s equator).In microgravity, this problem is removed.

Page 66: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

58

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Science in Personal and Social Perspectives∆ o Unifying Concepts and Processes

A surfactant is a substance added to a liquid to change itssurface tension. Surfactants are used in experiments where aliquid must wet its container in a particular way. A common useof surfactants is dishwashing detergent. The surfactant propertiesof the detergent is what causes food grease and oil to separatefrom most household dishware.

Two investigators had experiments conducted inthe Drop Physics Module. The Science andTechnology of Surface-Controlled PhenomenaExperiments had three major goals: to determinethe surface properties of liquids in the presenceof surfactants; to investigate the dynamicbehavior and the coalescence of droplets coatedwith surfactant materials; and to study theinteractions between droplets and acousticwaves. The shapes of oscillating drops recordedon videotape were analyzed frame by frame,revealing the variations of the oscillationamplitude with time. The frequency and dampingconstant of the droplet shape oscillations werecalculated. Analysis of the results is ongoing.

The goals of the Drop Dynamics Experiment wereto gather high-quality data on the dynamics ofliquid drops in microgravity for comparison withtheoretical predictions and to provide scientificand technical information needed for thedevelopment of new fields, such as containerlessprocessing of materials and polymerencapsulation of living cells. The experiments onthe USML-2 mission included breaking one dropinto two drops (bifurcation) and positioning adrop of one liquid at the center of a drop of adifferent liquid. Preliminary results show that theacoustic levitation technique has a stronginfluence on the drop bifurcation process.

Seven investigations were performed in theGlovebox on USML-2. These studies examinedvarious aspects of fluid behavior, combustion,and crystal growth. Two separate devices wereused for protein crystal growth experiments.

The Surface Tension Driven ConvectionExperiment investigated the basic fluid mechanicsand heat transfer of thermocapillary flowsgenerated by temperature variations along freesurfaces of liquids in microgravity. It determinedwhen and how oscillating flows were created.Preliminary analysis indicates that currenttheoretical models used to predict the onset ofoscillations are consistent with the experimentresults.

Page 67: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

59

The USML-2 Zeolite Crystal Growth experimentattempted to establish a quantitativeunderstanding of zeolite crystallization to allowcontrol of both crystal defect concentration andcrystallite size. The preliminary conclusionsindicate that, with few exceptions, the crystalsfrom USML-2 are larger in size than their Earth-grown counterparts and are twice as large asthose grown on previous Shuttle flights. Analysiswill continue to determine the effect of spaceprocessing on crystal defect concentration.

The projects that measured the microgravityenvironment added to the success of the missionby providing a complete picture of the Shuttle’senvironment and its disturbances. The OrbitalAcceleration Research Experiment (OARE)provided real-time quasi-steady acceleration datato the science teams. The Microgravity AnalysisWorkstation (MAWS) operated closely with theOARE instrument, comparing the environmentmodels produced by the MAWS with the actualdata gathered by the OARE. Two otherinstruments, the Space AccelerationMeasurement System and the Three DimensionalMicrogravity Accelerometer, took g-jittermeasurements throughout the mission. TheSuppression of Transient Events by Levitationdemonstrated a vibration isolation technology thatmay be suitable for experiments that are sensitiveto variations in the microgravity environment.

United States MicrogravityPayload-3,February 1996The third United States Microgravity Payloadmission launched on February 22 for 16 days ofresearch on orbit. During that time, microgravityresearch was conducted in the areas ofcombustion science, fluid physics, and materialsscience. The ultimate benefit of USMP-3 researchwill be improvements in products manufacturedon Earth. During the eight and one-half daysdedicated to microgravity science, researchersused telescience to control materials processingand thermodynamic experiments in the Cargo Bay

Science Standards

∆ o Physical Science∆ o Science and Technology∆ o Scienee in Personal and Social Perspectives∆ o Unifying Concepts and Processes

Zeolites are hydrous aluminum silicate minerals which alsocontain cations of sodium, potassium, calcium, strontium,barium, or a synthetic compound. They are commonly used asmolecular filters. For example, they are used to make every dropof gasoline sold in the United States.

The change in acceleration character seen in the middle of thisplot is due to a crew member swinging an experiment containeraround to mix its contents. Examination of the plot indicates thatthe crew member swung his arm around seven to eight times inten seconds.

Page 68: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

60

Vibration Frequencies Commonly Seen inOrbiter Accelerometer Data

Freq. (Hz) Disturbance Source

0.43 cargo bay doors3.5 Orbiter fuselage torsion3.66 structural frequency of Orbiter4.64 structural frequency of Orbiter5.2 Orbiter fuselage normal bending7.4 Orbiter fuselage lateral bending17 Ku band antenna dither20 experiment air circulation fan22 refrigerator freezer compressor38 experiment air circulation fan39.8 experiment centrifuge rotation speed43 experiment air circulation fan48 experiment air circulation fan53 experiment air circulation fan60 refrigerator piston compressor80 experiment water pump166.7 Orbiter hydraulic circulation pump

and astronauts performed combustion studies in the Middeck Glovebox.

The MEPHISTO science team used flight-provenequipment to learn how the chemical compositionof solidifying Sn-Bi alloys changes, and can becontrolled, during solidification. Such knowledgeapplies to ground-based materials processing.For the first time, the changes in the microgravityenvironment caused by carefully planned Shuttlethruster firings were correlated with the effects offluid flows in a growing crystal. With the help ofdata from the Space Acceleration MeasurementSystem, the experiment data showed that withthruster accelerations parallel to the crystal-meltinterface a large effect was noted, whereas whenthruster accelerations were perpendicular to theinterface there was little impact. Also, theMEPHISTO team successfully monitored the pointat which their sample’s crystal interfaceunderwent a key change-from flat to cellular (likethree dimensional ripples)-as it solidified.Measurements from the MEPHISTO facility willnow be analyzed, along with the final metallicsamples, in order to increase our understandingof subtle changes that occurred during thesamples’ solidification and subsequent cooling.

In the Advanced Automated DirectionalSolidification Furnace, three lead tin telluride(PbSnTe) crystals were grown while Columbiaorbited in three different attitudes, to determinehow these orientations affect crystal growth. Thisknowledge is expected to help researchersdevelop processes, and semiconductor materialsthat perform better and cost less to produce.

The Isothermal Dendritic Growth Experiment(IDGE) on USMP-3 achieved its missionobjectives. After collecting data to answer someof the questions opened by the USMP-2 results,research has shown that the small variations indendritic growth rates (how fast the tree-like solidpattern in a molten metal forms) measured inmicrogravity on the Space Shuttle are not due tovariations in the microgravity environment on

Page 69: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

61

orbit. The investigators are currently completingmeasurements on the three-dimensional shapeof these dendritic tips, which will furtheradvance the empirical basis from which moreaccurate solidification models are beingdeveloped and tested. This is an early step inwhat will ultimately be solidification models thatcould be used to make less expensive and morereliable cast or welded metal and alloy products.

The IDGE team also participated in an importanttechnology demonstration by commanding amicrogravity space instrument from a remotesite located at the Rensselaer PolytechnicInstitute. This first-ever remote commanding tothe Shuttle from a U.S. university campusforeshadows operations aboard the InternationalSpace Station.

Investigators for the Critical Fluid LightScattering Experiment were successful inobserving, with unprecedented clarity, xenon’scritical point behavior-the precise temperatureand pressure at which it exists as both a gas anda liquid. The transparent xenon sampledisplayed the unusual critical point condition,with maximum light scattering followed by asudden increase in cloudiness. This effect wasmuch more distinctive than observed during theUSMP-2 mission and happened at a lowertemperature than expected. Knowledge gainedfrom this experiment will prove valuable forapplications from liquid crystals tosuperconductors.

This mission was the first flight of a Gloveboxfacility in the Middeck section of the Shuttle.Three combustion science investigations wereconducted by the crew. The Forced FlowFlamespreading Test burned 16 paper samples,both flat and cylindrical. Video of the cylindricalsamples showed significant differences in flamesize, growth rate, and color with variations in airflow speed and fuel temperature. TheComparative Soot Diagnostics investigationcompleted 25 combustion experiment runs. The

As we move toward the era of the International Space Station,more experiment monitoring and control is being performed fromNASA centers and university laboratories “remote“ fromMarshall Space Flight Center and Johnson Space Center.

Glovebox Investigation Module hardware.

Page 70: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

62

The Space Shuttle Columbia, carrying the Life and MicrogravitySpacelab, launched from Kennedy Space Center June 20, 1996.

team obtained excellent results, testing theeffectiveness of two different smoke-sensingtechniques, for detecting fires aboard the Shuttleand the International Space Station. The RadiativeIgnition and Transition to Spread Investigationteam observed new combustion phenomena, suchas tunneling flames which move along a narrowpath instead of fanning out from the burn site.Also, for the first time, these investigators studiedthe effects of sample edges and corners on firespreading in microgravity.

Life and Microgravity Spacelab,June 1996The Life and Microgravity Spacelab missionsuccessfully completed a 17 day flight on July 6,1996. For this mission there was an unprecedenteddistribution of teams monitoring their experimentsaround the world, with experiment commandingperformed from three sites.

A number of researchers conducted experimentsusing the Advanced Gradient Heating Facility(AGHF) from the European Space Agency. Threealuminum-indium alloys were directionallysolidified to study the physics of solidificationprocesses in immiscible alloys called monotectics.The three samples, which differed only in indiumcontent, were processed at the same growth rateto permit a comparison of microstructures, howthe indium was distributed in the aluminum matrix.Two of these samples were of compositions whichcannot be processed under steady state conditionson Earth due to gravitationally-driven convectiveinstabilities and subsequent sedimentation of theliquid indium.

Another AGHF experiment used commercial Al-based samples to obtain insight into themechanism of particle redistribution duringsolidification. Additional studies were gearedtoward enhancement of the fundamentalunderstanding of the dynamics of insolubleparticles at solid/liquid interfaces. The physics ofthe problem is of direct relevance to such areas assolidification of metal matrix composites,

Page 71: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

63

management of defects such as inclusions andporosity in metal castings, development of hightemperature superconductor crystals withsuperior current carrying capacity, and thesolidification of monotectics.

A series of experiments was performed in theAdvanced Protein Crystallization Facility. Theexperiments were generally successful in terms ofyielding crystals. Those crystals which showedparticular promise, based on early microscopicexamination, were ferritin, satellite tobaccomosaic virus, satellite panicum mosaic virus,Iysozyme, and canavalin.

Several experiments were conducted using theBubble, Drop and Particle Unit (BDPU) from theEuropean Space Agency. In one experiment, thetransition to periodic and chaotic convection wasdetected. The results of this experiment willtrigger ground based research on the nonlineardynamics of convecto-diffusive systems. Inanother experiment, thermocapillary flows in twoand three layer systems were observed for fivetemperature gradients. The results of thisexperiment will improve our understanding ofheat and mass transfer in other fluid physicsresearch.

An additional experiment studied the interactionbetween pre-formed gas bubbles inside a solidand a moving solid/liquid interface, obtained byheating an initially solid sample. Early resultsconcerning the release of bubbles from themelting front indicate that once a hole has beenmade and the gas inside the bubble contacts theliquid then the liquid enters the cavity (by wettingthe solid walls) and pushes out the gas inside thebubble.

The scientific results of one set of BDPUexperiments provide us with new insights intobubble dynamics and into evaporation. This willlead to a better understanding and modeling ofsteam generation and boiling. Initial findings ofanother experiment showed that, under

Magnification of a sample of an aluminum-indium alloy. Whenthe sample is melted then controllably solidifies in the AGHF; theindium forms in cylindrical fibers within a solid aluminum matrix.

Page 72: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

64

Schematic diagram of Space Shuttle Orbiter docked to Mir.

microgravity conditions, boiling heat transfer isstill as efficient as under normal Earth gravity. Incontrast to the existing theory the findings showthat the influence of Earth gravity is less thanpredicted. The heat transfer in a microgravityenvironment is still as efficient, sometimes evenmore efficient than, at normal gravity.

Real-time Orbital Acceleration ResearchExperiment data were used by the science teamsto monitor the microgravity environment duringtheir experiment operations. The effects ofmission activities, such as venting of unneededwater and Orbiter orientation changes, werepresented to help the science teams understandthe environment in which their experimentsoperated. The Microgravity MeasurementAssembly (MMA) used this mission to verify anew system, augmented by a newly developedaccelerometer for measuring the quasi-steadyrange. MMA provided real-time quasi-steady andg-jitter data to the science teams during themission.

Shuttle/Mir Science Program,March 1995 to May 1998Although competition in the space program hasexisted between the United States and Russia forsome time, there has also been a rich history ofcooperation that has grown into the highlysuccessful joint science program that it is today.One part of that program is geared towardsmicrogravity research.

Many of the investigations from that program areconfigured to run in a Glovebox facility that hasbeen installed in the Priroda research module ofthe Mir Space Station. The Microgravity IsolationMount (MIM) is also located in Priroda. The MIMwas developed by the Canadian Space Agency toisolate experiments attached to it from ongoing g-jitter. The MIM is also able to induce definedvibrations so that the effects of specificdisturbances on experiments can be studied.Additional experiments are being performed inindividual experiment facilities that have beenplaced in the Priroda and other Mir modules.

Page 73: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

65

Various protein crystal growth experiments usethe Gaseous Nitrogen Dewar (GN2 Dewar).Samples are placed in the GN2 Dewar and it ischarged with liquid nitrogen, freezing them. Thesystem is designed so that the life of the nitrogencharge lasts long enough to get the payloadlaunched and into orbit. As the system absorbsheat, the nitrogen boils away and the chamberapproaches ambient temperature. As the samplesthaw, crystals start growing in the Dewar. Thecrystals are allowed to form throughout the longduration mission and are returned to Earth foranalysis. Initial investigations using the Dewarserved as a proof of concept for the experimentfacility. Successive experiment runs usingdifferent samples will continue to improve ourknowledge of protein crystal structures.

The Diffusion-Controled Crystallization Apparatusfor Microgravity experiment is designed primarilyfor the growth of protein crystals in amicrogravity environment. It uses the liquid/liquidand dialysis methods in which a precipitantsolution diffuses into a bulk solution. In theexperiment, a small protein sample is covered bya semipermeable membrane that allows theprecipitant solution to pass into the proteinsolution to initiate the crystallization process.Diffusion starts on Earth as soon as the chambersare filled. However, the rate is so slow that noappreciable change occurs before the samplesreach orbit one or two days later. Such anapparatus is ideally suited for the long durationMir missions.

The Cartilage in Space—Biotechnology Systemexperiment began with cell cultures beingtransported to Mir by the Shuttle in September1996 on mission STS-79. The investigation is atest bed for the growth, maintenance, and studyof long-term on-orbit cell growth in microgravity.The experiment investigates cell attachmentpatterns and interactions among cell cultures aswell as cellular growth and the cellular role informing functional tissue.

Protein and virus crystals grown in the GN2 Dewar on Mir.

Thaumatin Alpha Amylase

Creatine Kinase STMV

Ribonuclease RhombohedralCanavalin

Myoglobin Hemoglobin

Page 74: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

66

The Biotechnology System-Cartilage in Space Experiment inorbit. Top: Astronauts Carl Walz (left) and Jay Apt prepare theexperiment for transfer frorn the middeck of the Space ShuttleAtlantis to the Priroda module of Mir Bottom: Walz and Apt testthe bioreactor media for pH, carbon dioxide, and oxygen levels.

The Candle Flames in Microgravity investigationconducted 79 candle tests in the Glovebox in July1996. The experiments explored whether wickflames (candles) can be sustained in a purelydiffusive environment or in the presence of a veryslow, sub-buoyant convective flow. An associatedgoal was to determine the effect of wick size andcandle size on burning rate, flame shape andcolor, and to study interactions between twoclosely spaced diffusion flames. Preliminary dataindicate long-term survivability with evidence ofspontaneous and prolonged flame oscillationsnear extinction (when the candle goes out).

The Forced Flow Flame Spreading Tests ran in theGlovebox in early August 1996. The investigationsstudied flames spreading over solid fuels in low-speed air flows in microgravity. The effects ofvarying fuel thickness and flow velocity of flamesspreading in a miniature low-speed wind tunnelwere observed. The data are currently beinganalyzed and compared to theoretical predictionsof flame spreading. The numerical modelpredicted that the flame would spread at a steadyrate and would not experience changes in speed,shape, size, or temperature.

The Interface Configuration Experiment Gloveboxinvestigation studied how a liquid with a freesurface in contact with a container behaves inmicrogravity. This provides a basis for predictingthe locations and configurations of fluids with theuse of mathematical models. The data arecurrently being analyzed.

The Technological Evaluation of the MIM (TEM)was a technology demonstration to determine thecapabilities of the MIM. Through observations ofliquid surface oscillations, TEM evaluated theability of the MIM to impart controlled motions.The data are still being analyzed. A follow-ontechnology demonstration (TEM-2) wastransferred to Mir in September 1996.

Page 75: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

67

The Binary Colloidal Alloy Test Gloveboxinvestigation was also launched to Mir on STS-79in September 1996. The objective is to conductfundamental studies of the formation of gels andcrystals from binary colloid mixtures.

The Angular Liquid Bridge and Opposed FlowFlame Spread Glovebox investigations werecarried to Mir by the Shuttle on mission STS-81in early 1997. The former is an extension ofprevious fluid physics investigations conductedon the Shuttle and Mir and studies the behaviorand shape of liquid bridges, liquid that spans thedistance between two solid surfaces. Theobjective of the latter is to extend theunderstanding of the mechanisms by whichflames spread, or fail to spread, over solid fuelsurfaces in the presence of an opposing oxidizerflow.

A Space Acceleration Measurement System(SAMS) unit was launched to Mir on a Progressrocket in August 1994. Starting in October 1994,the SAMS was used to measure and characterizethe microgravity environment of various Mirmodules in support of microgravity experiments.Between October 1994 and September 1996,SAMS collected about sixty gigabytes ofacceleration data. The data have been used toidentify common vibration sources, as has beendone with the Shuttles. This information hashelped experimenters plan the timing and locationof their experiments. The Passive AccelerometerSystem is a simple tool that is being used toestimate the quasi-steady microgravityenvironment of Mir during the increment betweenSTS-79 and STS-81. The motion of a steel ball ina water-filled glass tube is tracked and thedistance travelled over time is used to estimateaccelerations caused by atmospheric drag and thelocation of the tube with respect to Mir’s center ofgravity.

Vibration Frequencies Commonly Seen inMir Accelerometer Data

Freq. (Hz) Disturbance Source 0.6 Kristall structural mode 1.0 Kristall structural mode 1.1 structural mode 1.2 structural mode 1.3 Kristall structural mode 1.9 Kristall structural mode 2.75 structural mode 3.75 structural mode

15 air quality system 24.1 humidifier/dehumidifier

30 air quality system harmonic41 fan

43.5 fan45 air quality system harmonic90 air quality system harmonic

166.6 gyrodyne (system used tomaintain Mir orientation)

Page 76: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

68

This illustration depicts the International Space Station in itscompleted and fully operational state with elements from theUnited States, Europe, Canada, Japan, and Russia.

FutureDirectionsMicrogravity science has come a long way sincethe early days of space flight when researchersrealized that they might be able to take advantageof the reduced gravity environment of orbitingspacecraft to study different phenomena. Shuttleand Mir based experiments that studybiotechnology, combustion science, fluid physics,fundamental physics, and materials science haveopened the doors to a better understanding ofmany of the basic scientific principles that drivemuch of what we do on Earth and in space.

To reach the next level of understanding aboutphenomena in a microgravity environment, weneed to perform experiments for longer periodsof time, to be able to conduct a series ofexperiments as is done on Earth, and to haveimproved environmental conditions. TheInternational Space Station is being developed asa microgravity research platform. Considerableattention has been given to the design of thestation and experiment facility components sothat experiments can be performed under high-quality microgravity conditions. The InternationalSpace Station will provide researchers withcontinuous, controlled microgravity conditions forup to thirty days at a time. (The time in betweenthese thirty day increments is used for vibration-intensive activities such as Shuttle dockings,station reconfiguration, and upkeep.) This isalmost twice as long as the microgravity periodsavailable on the Space Shuttle and there will be abetter environment than that provided by Mir. Thisincrease in experiment time and improvement inconditions will be conducive to improvedunderstanding of microgravity phenomena.

Continued microgravity research on the Shuttles,Mir, and on the International Space Station willlead to, among other things, the design of

Page 77: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

69

improved drugs, fire protection and detectionsystems, spacecraft systems, high-precisionclocks, and semiconductor materials. In addition,this research will allow us to create outposts onthe Moon where we can build habitats andresearch facilities. The end result of research inmicrogravity and on the Moon will be theincreased knowledge base necessary for our tripsto and exploration of Mars.

Page 78: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

71

Glossary

Acceleration–The rate at which an object’svelocity changes with time.

Altitude–Height above Earth’s mean sea level.

Apparent Weight–The net sum of all forces actingon a body is its apparent weight.

Biotechnology–Any technique that involves theresearch, manipulation, and manufacturing ofbiological molecules, tissues, and livingorganisms to improve or obtain products, orperform specific functions.

Buoyancy–Driven Convection Convection createdby the difference in density between two or morefluids in a gravitational field.

Capillarity–The attraction a liquid has for itselfversus the attraction it has for a solid surface,such as the liquid’s container.

Combustion Science–The study of the process ofburning.

Concave–Curved inward like the inner surface ofa sphere.

Convection–Energy and/or mass transfer in afluid by means of bulk motion of the fluid .

Convex–Curved like the outer surface of a sphere.

Critical Point–The temperature at which thedifferences between liquids and gases disappear.Above that temperature, the liquid smoothlytransforms to the gaseous state; boilingdisappears.

Dendrites–Branching structures that develop as amolten metal solidifies under certain conditions.

Density–The mass of a body divided by itsvolume (average density).

Differentiation–The process by which cells and/or tissues undergo a progressive specialization ofform or function.

Diffusion–lntermixing of atoms and/or moleculesin solids, liquids, and gases due to a difference incomposition.

Dopant–An impurity intentionally added to a puresemiconductor to alter its electronic or opticalproperties.

Drop Facility–Research facility that creates amicrogravity environment by permittingexperiments to freefall through an enclosedvertical tube.

Fluid–Anything that flows (liquid or gas).

Fluid Physics–The study of the properties andmotions of liquids, gases, and fluid-like solids.

Force–An action exerted upon a body in order tochange its state, either of rest, or of uniformmotion in a straight line.

Freefall–Falling in a gravitational field where theacceleration is the same as that due to gravityalone.

Fundamental Physics–The study of severalphysics subfields, including studies whereinteraction forces are weak, where extremelyuniform samples are required, where objectsmust be freely suspended and their accelerationmust be minimized, and where mechanicaldisturbances that are unavoidably present inEarth-bound laboratories must be eliminated.

Page 79: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

72

G–Universal Gravitational Constant (6.67x10-11 Nm2/kg2)

g–The acceleration Earth’s gravitational fieldexerts on objects at Earth’s surface(approximately 9.8 meters per second squared).

g-jitter–The vibrations experienced bymicrogravity experiments (for example onparabolic aircraft and the Space Shuttle) thatcause effects similar to those that would becaused by a time-varying gravitational field.

Gradient–The variation of a quantity such astemperature with respect to a given parameter,typically distance, °C/cm.

Gravitation–The attraction of objects due to theirmasses.

Homogeneous–Uniform in structure and/orcomposition.

Immiscible–The situation where two or moreliquids do not mix chemically.

Inertia–A property of matter that causes it toresist changes in velocity.

Joule Heating–Heating a material by flowing anelectric current through it.

Law of Universal Gravitation–A law stating thatevery mass in the universe attracts every othermass with a force proportional to the product oftheir masses and inversely proportional to thesquare of the distances between their centers.

Materials Science–The study of developingquantitative and predictive relationships betweenthe processing, structure, and properties ofmaterials.

Microgravity (µg)–An environment in which theapparent weight of a system is small compared toits actual weight (due to gravity).

Morphology–The form and structure of an object.

Nucleus–A source upon which something, suchas a crystal, grows or develops.

Quasi-steady Acceleration–Accelerations inspacecraft related to the position in thespacecraft, aerodynamic drag, and vehiclerotation.

Regolith–A layer of powder-like dust and looserock that rests on bedrock. In the case of themoon, fragmentation of surface rocks bymeteorite bombardment created much of theregolith material.

Rheology–The scientific study of the deformationand flow of matter.

Satellite–A natural or man-made object thatorbits a celestial body.

Semiconductor–A substance, such as germaniumand silicon, that is a poor electrical conductor atroom temperature but is improved by minuteadditions of certain substances (dopants) or bythe application of heat, light, or voltage; a materialwith a forbidden energy gap less than 3 eV.

Page 80: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

73

Skylab–NASA’s first orbital laboratory that wasoperated in 1973 and 1974.

Spacelab–A scientific laboratory developed bythe European Space Agency that is carried intoEarth orbit in the Space Shuttle’s payload bay.

Speed–The magnitude of velocity.

Surfactant–A substance added to a liquid tochange its surface tension.

Velocity–The rate at which the position of anobject changes with time; it is a vector quantity.

Weight–The weight of an object is thegravitational force exerted on it by Earth.

Page 81: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

75

Activities

Activity Matrix .................................................................................................................................. 76

Microgravity In The Classroom........................................................................................................ 79

Accelerometers ................................................................................................................................ 88

Around The World ........................................................................................................................... 95

Inertial Balance .............................................................................................................................. 101

Gravity-Driven Fluid Flow............................................................................................................... 109

SurfaceTension-Driven Flows ........................................................................................................ 114

Temperature Effects on Surface Tension ........................................................................................ 119

Candle Flames ............................................................................................................................... 124

Candle Flames in Microgravity ....................................................................................................... 129

Crystallization Model ..................................................................................................................... 135

Crystal Growth and Buoyancy-Driven Convection Currents ........................................................... 141

Rapid Crystallization ...................................................................................................................... 148

Microscopic Observation of Crystal Growth .................................................................................. 152

Zeolite Grystal Growth ................................................................................................................... 159

Page 82: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

76

Activity MatrixStandards and Skills

Science

as Inquiry

Physica

l Scie

nce

-position & m

otion of o

bjects

- propertie

s of o

bjects and m

aterials

Unifying C

oncepts

& Process

es

Change, Consta

ncy, & M

easurement

- evid

ence, m

odels, & exp

lanation

Science

& Tech

nology

- abiliti

es of te

chnologic

design

- underst

anding about scie

nce & te

chnology

Science

in Perso

nal & Socia

l Persp

ective

s

Science

& Tech

nology in Loca

l Challe

nges

Science Standards

Microgravity In The Classroom

Accelerometers

Around The World

Inertial Balance

Gravity-Driven Fluid Flow

Surface Tension-Driven Flows

Temp. Effects on Surface........

Candle Flames

Candle Flames in Microgravity

Crystallization Model

Crystal Growth and Buoy.....

Rapid Crystallization

Microscopic Observation of....

Zeolite Crystal Growth

Observi

ng

Communicatin

g

Measurin

g

Collectin

g Data

Inferring

Predicting

Making M

odels

Making G

raphs

Hypothesiz

ing

Interpreting Data

Controllin

g Variables

Defining O

perationally

Investig

ating

Science Process Skills

Microgravity In The Classroom

Accelerometers

Around The World

Inertial Balance

Gravity-Driven Fluid Flow

Surface Tension-Driven Flows

Temp. Effects on Surface........

Candle Flames

Candle Flames in Microgravity

Crystallization Model

Crystal Growth and Buoy.....

Rapid Crystallization

Microscopic Observation of....

Zeolite Crystal Growth

Page 83: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

77

Problem Solving

Communicatio

n

Reasoning

Connections

Number & Number R

elationsh

ips

Computation & Estim

ation

Patterns &

Functions

Statistics

Probability

Geometry

Mathematics Standards

Microgravity In The Classroom

Accelerometers

Around The World

Inertial Balance

Gravity-Driven Fluid Flow

Surface Tension-Driven Flows

Temp. Effects on Surface........

Candle Flames

Candle Flames in Microgravity

Crystallization Model

Crystal Growth and Buoy.....

Rapid Crystallization

Microscopic Observation of....

Zeolite Crystal Growth

Page 84: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

79

Objective:

• To demonstrate how microgravity iscreated by freefall.

Science Standards:Science as InquiryPhysical Science- position and motion of objectsChange, Constancy, & Measurement- evidence, models, & exploration

Science Process Skills:ObservingCommunicatingMaking ModelsDefining OperationallyInvestigatingPredictingMathematics Standards:Computation & EstimationMeasurement

Activity Management:This activity consists of three demonstrations thatcreate microgravity conditions by freefall. Althoughthe first demonstration is best done by the teacher,the other demonstrations can be done as activities bystudents working in groups of three or four.

Each demonstration requires a clear space wheredrop tests can be conducted. Two of thedemonstrations require water and you should have amop, sponges, or paper towels available to clean upany mistakes.

Begin with the Falling Weight apparatus teacherdemonstration. Before dropping the device, conduct adiscussion with the students to consider possibleoutcomes. Ask students to predict what they thinkwill happen when the device is dropped. Students willfocus on the proximity of the balloon and the needle.

ScrewsScrews

Screws

Various objects demonstrate microgravity as they aredropped.

Falling weight apparatus(see special instructions)

Plastic cupSmall cookie sheet orplastic cutting boardEmpty soft drink canNail or some other punchCatch basin - plastic dish

pan, bucket, large wastebarrel

Mop, paper towels, orsponges for cleanup

Will the balloon break when the device isdropped? If the balloon does break, willit break immediately or when the devicehits the floor? Try to get students withdifferent predictions to debate eachother. After the debate, drop the device.

Microgravity In The Classroom

MAT

ER

IALS

AN

D T

OO

LS

Page 85: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

80

Be sure to hold the wooden frame by the middleof the top cross piece. Hold it out at arm’s lengthin case the weight and needle bounce your way.

Discuss the demonstration to make sure thestudents understand why the balloon poppedwhen it did. Before trying any of the otherdemonstrations, student groups should read thestudent reader entitled Microgravity.

The second and third demonstrations can also bedone by the teacher or by small groups ofstudents. One student drops or tosses the testitem and the other students observe whathappens. Students should take turns observing.

Assessment:Have students write a paragraph or two thatdefine microgravity and explain how freefallcreates it.

Extensions:1. Videotape the demonstrations and play back

the tape a frame at a time. Since each secondof videotape consists of 30 frames, the tapecan be used as a simple timing device. Counteach frame as onethirtieth of a second.

2. Replace the rubber bands in the falling weightapparatus with heavy string and drop theapparatus again to see whether the balloonwill break. Compare the results of the twodrops.

3. Conduct a microgravity science field trip to anamusement park that has roller coasters andother rides that involve quick drops. Getpermission for the students to carry acceler-ometers on the rides to study the gravityenvironments they experience. On a typicalrollercoaster ride, passengers experiencenormal g (gravity), microgravity, high g, andnegative g.

Page 86: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

81

Gravity is an attractive force that all objects havefor one another. It doesn’t matter whether theobject is a planet, a cannonball, a feather, or aperson. Each exerts a gravitational force on allother objects around it.

The amount of force between two objectsdepends upon how much mass each contains andthe distance between their centers of mass. Forexample, an apple hanging from a tree branch willhave less gravitational force acting on it thanwhen it has fallen to the ground. The reason forthis is because the center of mass of an apple,when it is hanging from a tree branch, is fartherfrom the center of mass of Earth than when Iyingon the ground.

Student Reader - 1

Microgravity

Although gravity is a force that is always with us,its effects can be greatly reduced by the simpleact of falling. NASA calls the condition producedby falling microgravity.

You can get an idea of how microgravity iscreated by looking at the diagram below. Imagineriding in an elevator to the top floor of a very tallbuilding. At the top, the cables supporting the carbreak, causing the car and you to fall to theground. (In this example, we discount the effectsof air friction on the falling car.) Since you and theelevator car are falling together, you feel like youare floating inside the car. In other words, youand the elevator car are accelerating downward atthe same rate due to gravity alone. If a scale werepresent, your weight would not register because

the scale would be falling too.The ride is lots of fun until youget to the bottom.

NASA uses several differentstrategies for conductingmicrogravity research. Eachstrategy serves a differentpurpose and produces amicrogravity environment withdifferent qualities. One of thesimplest strategies is the use ofdrop towers. A drop tower is likea high-tech elevator shaft. A smallexperiment package is suspendedfrom a latch at the top. Thepackage contains the experiment,television or movie cameras, anda radio or wire to transmit dataduring the test. For some droptowers, when the test is ready, airfrom the shaft is pumped out so

Normalweight

Heavierthan normal

Lighterthan normal

No apparentweight

The person in the stationary elevator car experiences normal weight. Inthe car immediately to the right, weight increases slightly in the next carbecause of the downward acceleration. No weight is measured in thelast car on the right because of freefall.

Page 87: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

82

the package will fall more smoothly. The cameras,recording equipment, and data transmitter areturned on as a short countdown commences.When T minus zero is reached, the package isdropped.

NASA has several drop tower facilities includingthe 145 meter drop tower at the NASA LewisResearch Center in Cleveland, Ohio. The shaft is6.1 meters in diameter and packages fall 132meters down to a catch basin near the shaft’sbottom. For 5.2 seconds, the experiment

experiences a microgravity environment that isabout equal to one one-hundred-thousandth(lx10-5) of the force of gravity experienced whenthe package is at rest.

If a longer period of microgravity is needed, NASAuses a specially equipped jet airplane for the job.Most of the plane’s seats have been removed andthe wall, floor, and ceiling are covered with thickpadding similar to tumbling mats.

One of the advantages of using an airplane to domicrogravity research is that experimenters canride along with their experiments. A typical flightlasts 2 to 3 hours and carries experiments andcrew members to a beginning altitude about 7kilometers above sea level. The plane climbsrapidly at a 45-degree angle (pull up) and followsa path called a parabola. At about 10 kilometershigh, the plane starts descending at a 45-degreeangle back down to 7 kilometers where it levelsout (pull out). During the pull up and pull outsegments, crew and experiments experience aforce of between 2 g and 2.5 g. The microgravityexperienced on the flight ranges between oneone-hundredth and one one-thousandth of a g.On a typical flight, 40 parabolic trajectories areflown. The gut-wrenching sensations producedon the flight have earned the plane the nicknameof “Vomit Comet.”

Student Reader - 2

For the first few seconds of the pull up, theexperiments and experimenters onboard the airplanefeel a gravity force of about two times normal. Duringthe upper portion of the parabola, microgravity isproduced that ranges from one onehundredth to oneone-thousandth of a g. During the pull out, the gravityforce again reaches about two times normal.

A parabola is the mathematical shape you get if youslice a cone in the way shown in the picture.

Page 88: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

83

Small rockets provide a third technology forcreating microgravity. A sounding rocket follows aparabolic path that reaches an altitude hundredsof kilometers above Earth before falling back. Theexperiments onboard experience several minutesof freefall. The microgravity environmentproduced is about equal to that produced onboardfalling packages in drop towers.

Although airplanes, drop facilities, and smallrockets can be used to establish a microgravityenvironment, all of these laboratories share acommon problem. After a few seconds orminutes of low-g, Earth gets in the way and thefreefall stops. When longer term experiments(days, weeks, months, and years) are needed, it isnecessary to travel into space and orbit Earth. Wewill learn more about this later.

Student Reader -3

Typical design of a sounding rocket used formicrogravity research.

Launch

High-g acceleration

Payload separation

Microgravity

Parabolic Trajectory

Deceleration

Recovery

Telemetry

Microgravity begins when the rocket arrives aboveEarth’s atmosphere and the payload section isreleased. Microgravity ends when the payload fallsback into the atmosphere and begins feelingatmospheric drag.

In a few years, it will be possible to conductsensitive microgravity experiments, lastingmany months, on the International SpaceStation.

Page 89: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

84

Falling WeightApparatus

Construction:1. Assemble the rectangular supporting frame as

shown in the diagram. Be sure to drill pilotholes for the screws and glue the framepieces before screwing them together. Bracethe front and back of each corner with smalltriangles of plywood. Glue and nail them inplace.

2. Drill a 1/2 inch-diameter hole through thecenter of the top of the frame. Be sure thehole is free of splinters.

3. Twist the two screw eyes into the underside ofthe top of the frame as shown in the diagram.(Before doing so, check to see that the metalgap at the eye is wide enough to slip a rubberband over it. If not, use pliers to spread thegap slightly.)

4. Join three rubber bands together and thenloop one end through the metal loop of thefishing sinker.

5. Follow the same procedure with the otherthree rubber bands. The fishing weight shouldhang downward like a swing, near the bottomof the frame as shown in the illustration. If theweight hangs near the top, the rubber bandsare too strong. Replace them with thinnerrubber bands. If the weight touches thebottom, remove some of the rubber bands.

6. Attach the needle to the weight, with the pointupward. There are several ways of doing thisdepending upon the design of the weight. Ifthe weight has a loop for attaching it tofishing line, hold the needle next to the loopwith tape or low-temperature hot glue.Another way of attaching the needle is to drilla small hole on top of the weight to hold theneedle.

ScrewsScrews

Screws

MAT

ER

IALS

AN

D T

OO

LS

MATERIALS NEEDED:2 pieces of wood 16x2x1 in.2 pieces of wood 10x2x1 in.4 wood screws (#8 or #10 by 2 in.)8 corner brace triangles from 1/4 in.

plywoodGlue2 screw eyes4-6 rubber bands1 6-oz fishing sinker or several

lighter sinkers taped togetherLong sewing needleSmall round balloons (4 in.)StringDrill, 1/2 in. bit, and bit for piloting

holes for wood screwsScrewdriverPillow or chair cushion(Optional - Make a second frame with

string supporting the sinker.)

Page 90: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

85

Explanation:When stationary, the lead fishing weight stretchesthe rubber bands so the weight hangs near thebottom of the frame. When the frame is dropped,the whole apparatus goes into freefall. Themicrogravity produced by the fall removes theforce the fishing weight is exerting on the rubberbands. Since the stretched rubber bands have noforce to counteract their tension, they pull theweight—with the needle—up toward the balloon,causing it to pop. (In fact, the sinker’sacceleration toward the balloon will initially bezero due to the energy released as the rubberbands relax to their normal, unstretched length.)If a second frame, with string instead of rubberbands supporting the weight, is used forcomparison, the needle will not puncture theballoon as the device falls because the strings willnot rebound like the rubber bands did.

In tests of this device using a television cameraand videotape machine as a timer (seeextensions), the balloon was found to pop inabout 4 frames which is equal to fourthirtieths ofa second or 0.13 seconds. Using the formula for afalling body (see below), it was determined thatthe frame dropped only about 8 centimetersbefore the balloon popped. This was the same asthe distance between the balloon and the needlebefore the drop.

d = 1 2

d = 1 2

d is the distance of the fall in metersa is the acceleration of gravity in meters persecond squaredt is the time in seconds

Use:Inflate the balloon and tie off the nozzle with ashort length of string. Thread the string throughthe hole and pull the balloon nozzle through. Pullthe string snugly and tape it to the top of theframe.

Demonstration:1. Place a pillow or cushion on the floor. Hold

the frame above the pillow or cushion atshoulder level.

2. Ask the students to predict what will happenwhen the entire frame is dropped.

3. Drop the entire unit onto the cushion. Theballoon will pop almost immediately afterrelease.

at 2

x 9.8 m/s2x( 0.13s)2=0 08m

Page 91: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

86

Procedure:1. Place the catch basin in the center of an open

area in the classroom.2. Fill the cup with water.3. Place the cookie sheet over the opening of the

cup. Press the cup tight to the sheet whileinverting the sheet and cup.

4. Hold the cookie sheet and cup high above thecatch basin. You may wish to stand on a sturdytahle or climb on a stepladder to raise the cuphigher.

5. While holding the cookie sheet level, slowlyslide the cup off the edge of the cookie sheetand observe what happens.

6. Refill the cup with water and invert it on thecookie sheet.

7. Quickly pull the cookie sheet straight out fromunder the cup and observe the fall of the cupand water.

8. (Optional) Videotape the cup drop and playback the tape frame-to-frame to observe whathappens to the water.

Explanation:Air pressure and surface tension keep the waterfrom seeping around the cup’s edges while it isinverted on the cookie sheet. If the cup wereslowly pushed over the edge of the sheet, thewater would pour out. However, when the sheet isquickly pulled out from under the filled cup, thecup and water both fall at the same time. Sincethey are both accelerated downward by gravity anequal amount, the cup and water fall together. Thewater remains in the cup but the lower surface ofthe water bulges. Surface tension tends to drawliquids into spherical shapes. When liquids are atrest, gravity overcomes surface tension, causingdrops to spread out. In freefall, gravity’s effectsare greatly reduced and surface tension begins todraw the water in the cup into a sphere.

Falling Water

MAT

ER

IALS

AN

D T

OO

LS

Plastic drinking cupCookie sheet (with at least one edgewithout a rim)Catch basin (large pail, waste basket)WaterChair or stepladder (optional)TowelsTelevision camera, videotaperecorder, and monitor (optional)

Page 92: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

87

Procedure:1. Punch a small hole with a nail near the bottom

of an empty soft drink can.2. Close the hole with your thumb and fill the can

with water.3. While holding the can over a catch basin,

remove your thumb to show that the water fallsout of the can.

4. Close the hole again and stand back about 2meters from the basin. Toss the can through theair to the basin, being careful not to rotate thecan in flight.

5. Observe the can as it falls through the air.6. (Optional) Videotape the can toss and play back

the toss frame-to-frame to observe the hole ofthe can.

Explanation:When the can is stationary, water easilypours out of the small hole and falls to thecatch basin. However, when the can is tossed,gravity’s effects on the can and its contents aregreatly reduced. The water remains in the canthrough the entire fall including the upwardportion. This is the same effect that occurs onaircraft flying in parabolic arcs.

Can Throw

MAT

ER

IALS

AN

D T

OO

LS

Empty aluminum soft drink canSharp nailCatch basinWaterTowelsTelevision camera, videotape

recorder, and monitor (optional)

Page 93: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

88

Objective:• To measure the acceleration

environments created by differentmotions.

Science Standards:Physical Science- position and motion of objectsUnifying Concepts and ProcessesChange, Constancy, & MeasurementScience and Technology- abilities of technological design

Science Process Skills:CommunicatingMeasuringCollecting Data

Mathematics Standards:CommunicationNumber & Number RelationshipsMeasurement Computation &Estimation

Activity Management: This activity provides students with theplans for making a one-axisaccelerometer that can be used tomeasure acceleration in differentenvironments ranging from +3 g to -3 g.The device consists of a triangular shapedposter board box they construct with alead fishing sinker suspended in itsmiddle with a single strand of a rubberband. Before using the device, studentsmust calibrate it for the range ofaccelerations it can measure.

The pattern for making the accelerometerbox is included in this guide. It must bedoubled in size. It is recommended that

Accelerometers

-3

-2

-1

0

1

2

3

Students construct a device that can measureacceleration environments from +3 to -3 9.

MAT

ER

IALS

AN

D T

OO

LS

Lightweight poster board(any color)

3 “drilled egg” lead fishingsinkers, 1 ounce size

Masking tapeRubber band, #19 size4 small paper clipsScissorsStraightedgeBallpoint penPatternHot glue (low temperature)

several patterns be available for the students toshare. To save on materials, students can work inteams to make a single accelerometer. Old filefolders can be substituted for the poster board.The student reader can be used at any time duringthe activity.

Page 94: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

89

The instructions call for three egg (shaped)sinkers. Actually, only one is needed for theaccelerometer. The other two are used forcaiibrating the accelerometer and can be sharedbetween teams.

When the boxes are being assembled, the threesides are brought together to form a prism shapeand held securely with masking tape. The endsshould not be folded down yet. A rubber band iscut and one end is inserted into a hole punchedinto one of the box ends. Tie the rubber band to asmall paper clip. This will prevent the end of therubber band from sliding through the hole. Theother end of the rubber band is slipped throughthe sinker first and then tied off at the other endof the box with another paper clip. As each rubberband end is tied, the box ends are closed and heldwith more tape. The two flaps on each endoverlap the prism part of the box on the outside.It is likely that the rubber band will need someadjustment so it is at the right tension. This canbe easily done by rolling one paper clip over sothe rubber band winds up on it. When the rubberband is lightly stretched, tape the clip down.

After gluing the sinker in place on the rubberband, the accelerometer must be calibrated. Theposition of the sinker when the box is standing onone end indicates the acceleration of 1 gravity (1g). By making a paper clip hook, a second sinkeris hung from the first and the new position of thefirst sinker indicates an acceleration of 2g9. Athird sinker indicates 3 g. Inverting the box andrepeating the procedure yields positions fornegative 1, 2, and 3 g. Be sure the studentsunderstand that a negative g acceleration is anacceleration in a direction opposite gravity’s pull.Finally, the half way position of the sinker whenthe box is laid on its side is 0 g.

Students are then challenged to use theiraccelerometers to measure various accelerations.They will discover that tossing the device orletting it fall will cause the sinker to move, but itwill be difficult to read the scale. It is easier to

read if the students jump with the meter. In thiscase, they must keep the meter in front of theirfaces through the entire jump. Better still wouldbe to take the accelerometer on a fast elevator, ona trampoline, or a roller coaster at an amusementpark.

Assessment:Test each accelerometer to see that it isconstructed and calibrated properly. Collect andreview the student sheets.

Extensions:1. Take the accelerometer to an amusement park

and measure the accelerations

Magnetic AccelerometerThree ring magnets with like poles facing each other.

you experience riding a roller coaster and otherfast rides.

2. Construct a magnetic accelerometer.3. Design and construct an accelerometer for

measuring very slight accelerations such asthose that might be encountered on the SpaceShuttle.

2

1

0

1

2

Mag

neti

c Po

le A

rran

gem

ent

2

1

0

1

2

NS

SN

NS

Page 95: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

90

Accelerometer Box Pattern

5 cm 5 cm5 cm5 cm

27 c

m

2 cm

19 c

m

5 cm

4 cm

Enlarge 2X

Hole for rubberband

Hole for rubberband

4 cm

Page 96: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

91

Acceleration is the rate at which an object’s velocity is changing. The change can be in howfast the object is moving, a direction change, or both. If you are driving an automobile andpress down on the gas pedal (called the accelerator), your velocity changes. Let’s say yougo from 0 kilometers to 50 kilometers per hour in 10 seconds. Your acceleration is said tobe 5 kilometers per hour per second. In other words, each second you are going 5kilometers per hour faster than the second before. In 10 seconds, you reach 50 kilometersper hour.

You feel this acceleration by being pressed into the back of your car seat. Actually, it is thecar seat pressing against you. Because of the property of inertia, your body resistsacceleration. You also experience acceleration when there is a change in direction. Let’s sayyou are driving again but this time at a constant speed in a straight line. Then, the roadcurves sharply to the right. Without changing speed, you make the turn and feel your bodypushed into the left wall of the car. Again, it is actually the car pushing on you. This time,your acceleration was a change in direction. Can you think of situations in whichacceleration is both a change in speed and direction?

The reason for this discussion on acceleration is that it is important to understand that theforce of gravity produces an acceleration on objects. Imagine you are standing at the edgeof a cliff and you drop a baseball over the edge. Gravity accelerates the ball as it falls. Theacceleration is 9.8 meters per second per second. After 5 seconds, the ball is traveling at arate of nearly 50 meters per second. To create a microgravity environment where theeffects of gravity on an experiment are reduced to zero, NASA would have to acceleratethat experiment (make it fall) at exactly the same rate gravity does. In practice, this is hardto do. When you jump into the air, the microgravity environment you experience is about1/100th the acceleration of Earth’s gravity. The best microgravity environment that NASA’sparabolic aircraft can create is about 1/1000th g. On the Space Shuttle in Earth orbit,microgravity is about one-millionth g. In practical terms, if you dropped a ball there, theball would take about 17 minutes just to fall 5 meters!

Accelerat oi n

Gravity

Student Reader - 1

Page 97: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

92

The instructions below are for making a measuring device called an accelerometer. Accelerometers areused to measure how fast an object changes its speed in one or more directions. This accelerometeruses a lead weight suspended by a rubber band to sense changes in an object’s motion.

Student Worksheet - 1

Accelerometer Constructionand Calibration

Building the Accelerometer:1. Trace the pattern for the accelerometer on a

piece of poster board. Cut out the pattern.2. Use a ruler and a ballpoint pen to draw the fold

lines on the poster board in the same placethey are shown on the pattern. As you draw thelines, apply pressure to the poster board. Thiswill make the poster board easier to fold.

3. Fold the two long sides up as shown in the firstillustration. The left side with the tabs is foldedover first. The right side is folded second. Thismakes a long triangle shape. Use tape to holdthe sides together.

4. Punch a small hole in one of the end triangles.Cut the rubber band to make one long elasticband. Tie one end of the band to a small paperclip. Thread the other end through the hole.

5. Slip the lead weight on the band. Punch a holein the other end triangle. While stretching theband, slip the free end through the second holeand tie it to a second paper clip.

6. Set the triangular box on its side so the windowis up. Slide the weight so it is in the middle ofthe elastic band. Put a dab of hot glue on eachend of the weight where the elastic band entersthe holes.

7. If the elastic band sags inside the box, roll theelastic around one of the paper clips until it issnug. Then tape the paper clip in place. Tapethe other triangular end in place.

Fold this side first.The two flaps are onthe inside. Fold this side

second and tapeto hold.

Page 98: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

93

Calibrating the Accelerometer:1. Stand the accelerometer on one end. Using a

pencil, mark one side of the accelerometer nextto the middle of the weight. Identify this markas 1 g.

2. Using a small paper clip as a hook, hang asecond weight on the first. Again, mark themiddle of the first weight on the accelerometer.Identify this mark as 2 g. Repeat this step witha third weight and identify the mark as 3 g.

3. Remove the two extra weights and stand theaccelerometer on its other end. Repeat themarking procedure and identify the marks as -1 g, -2 g, and -3 g.

4. The final step is to mark the midway positionbetween 1 and -1 g. Identify this place as 0 g.The accelerometer is completed.

Student Worksheet - 2

Fold ends after rubber band andweight are attached. The two flapson each end are folded to the outside.

Tape

Tape

-3

-2

-1

0

1

2

3

Finished Accelerometer

Page 99: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

94

Instrument Construction Team:

Student Worksheet - 3

Accelerometer Tests

Test your accelerometer by jumping in the airwith it a few times. What happens to the positionof the sinker?

What g forces did you encounter in your jumps?

Where else might you encounter g forces likethese?

Explain how your accelerometer measuresdifferent accelerations.

Design Activity:How can this accelerometer be redesigned so it is more sensitive to slight accelerations?Make a sketch of your idea below and write out a short explanation.

Page 100: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

95

Objective:

• To create a model of how satellites orbitEarth.

Science Standards:Science as InquiryPhysical Science- position and motion of objectChange, Constancy, & Measurement- evidence, models, & exploration

Science Process Skills:ObservingCommunicatingMaking ModelsDefining Operationally Investigating

Mathematics Standards:CommunicationGeometry

Activity Management:This activity can be conducted as ademonstration or a small group activity at alearning station where student groups taketurns.

Pick a small ball to which it is easy toattach a string. A small slit can be cut intoa tennis ball or racquetball with a sharpknife. Then, a knotted string can be shovedthrough the slit. The slit will close aroundthe string. A screw eye can be screwed intoa solid rubber or wood ball and a stringattached to it.

If using this as an activity, have studentswork in groups of two. The large ball andflowerpot should be placed on the floorinan open area. Tell students to imagine the

Around The World

A ball on a string circles a ball to simulatethe orbits of satellites around Earth.

MAT

ER

IALS

AN

D T

OO

LS Large ball*Small ball2 meters of stringFlower pot*

* A world globe can substitutefor the large ball and flower pot

ball is Earth with its north pole straight up. Onestudent will stand near the ball and pot and holdthe end of the string the small ball is attached to.This student’s hand should be held directly overthe large ball’s north pole, and enough stringshould be played out so that the small

Page 101: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

96

ball comes to rest where the large ball’s equatorshould be. While the first student holds the stringsteadily the second student starts the small ballmoving. The objective is to move the small ball ina direction and at a speed that will permit it toorbit the big ball.

Save the student reader for use after studentshave tried the activity.

Additional Information:This model of a satellite orbiting around Earth iseffective for teaching some fundamentals oforbital dynamics. Students will discover that theway to orbit the small ball is to pull it outward ashort distance from the large ball and then start itmoving parallel to the large ball’s surface. Thespeed they move it will determine where the ballends up. If the small ball moves too slowly, it willarc “down” to Earth’s surface. NASA launchesorbital spacecraft in the same way. They arecarried above most of Earth’s atmosphere andaimed parallel to Earth’s surface at a particularspeed. The speed is determined by the desiredaltitude for the satellite. Satellites in low orbitsmust travel faster than satellites in higher orbits.

In the model, the small ball and string become apendulum. If suspended properly, the at-restposition for the pendulum is at the center of thelarge ball. When the small ball is pulled out andreleased, it swings back to the large ball.Although the real direction of gravity’s pull isdown, the ball seems to move only in a horizontaldirection. Actually, it is moving downward as well.A close examination of the pendulum reveals thatas it is being pulled outward, the small ball is alsobeing raised higher off the floor.

The validity of the model breaks down whenstudents try orbiting at different distances fromthe large ball without adjusting the length of thestring. To make the small ball orbit at a higheraltitude without lengthening the string, the ballhas to orbit faster than a ball in a lower orbit. Thisis the opposite of what happens with realsatellites.

Assessment:Use the student pages for assessment.

Extensions:1. Investigate the mathematical equations that

govern satellite orbits such as the relationshipbetween orbital velocity and orbital radius.

2. Learn about different kinds of satellite orbits(e.g., polar, geostationary, geosynchronous)and what they are used for.

3. Look up the gravitational pull for differentplanets. Would there be any differences inorbits for a planet with a much greatergravitational pull than Earth’s? Less thanEarth’s?

4. Use the following equation to determine thevelocity a satellite must travel to remain inorbit at a particular altitude:

v = velocity of the satellite in metersGM = gravitational constant times Earth’s mass

(3.99x1014 meters 3/sec2 )r = Earth’s radius (6.37x106 meters) plus the

altitude of the satellite

GM

rV =

Page 102: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

97

A microgravity environment is created by lettingthings fall freely. NASA uses airplanes, droptowers, and small rockets to create a microgravityenvironment lasting a few seconds to severalminutes. Eventually, freefall has to come to anend because Earth gets in the way. Whenscientists want to conduct experiments lastingdays, weeks, months, or even years, it isnecessary to travel into space and orbit Earth.Having more time available for experimentsmeans that slower processes and more subtleeffects can be investigated.

To see how it is possible to establish microgravityconditions for long periods of time, it is firstnecessary to understand what keeps a spacecraftin orbit. Ask just about anybody what keepssatellites and Space Shuttles in orbit and you willprobably hear, “There is no gravity in space.” Thisis simply not true. Gravity is what keeps a satelliteor Space Shuttle from drifting into space. It doesthis by bending an orbiting object’s path into acircular shape. To explain how this works, we canuse an example presented by English scientist SirIsaac Newton. In a book he wrote in 1673,Philosophiae Naturalis Principia Mathematica(Mathematical Principles of Natural Philosophy),Newton explained how a satellite could orbitEarth.

Newton’s cannon fires the first cannonball. The combinationof the cannonball’s initial velocity and the pull of Earth’sgravity causes the cannonball to arc to the ground near themountain.

Student Reader - 1

Aro

und The World

ResultingPath

Gravity

Initial Direction

Gravity

A second cannonball is fired using a larger charge of blackpowder. The force exerted on the cannonball causes it totravel faster than the first cannonball. Gravity bends its pathinto an arc but because of the greater speed, the cannonballtravels farther before it lands on Earth.

Newton envisioned a very tall mountain on Earthwhose peak extended above Earth’s atmosphere.This was to eliminate friction with Earth’satmosphere. Newton then imagined a cannon atthe top of that mountain firing cannonballsparallel to the ground. As each cannonball was

GreaterForce

Gravity

Page 103: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

98

Gravity

GreaterForce

Gravity

GreaterForce

Student Reader - 2

fired, it was acted upon by two forces. One force,due to the explosion of the black powder,propelled the cannonball straight outward. If noother force were to act on the cannonball, theshot would travel in a straight line and at aconstant velocity. But Newton knew that a secondforce would also act on the cannonball: Earth’sgravity would cause the path of the cannonball tobend into an arc ending at Earth’s surface.

Newton demonstrated how additional cannonballswould travel farther from the mountain if thecannon were loaded with more black powder eachtime it was fired. With each shot, the path wouldlengthen and soon the cannonballs woulddisappear over the horizon. Eventually, if acannonball were fired with enough energy itwould fall entirely around Earth and come back toits starting point. This would be one compieteorbit of Earth. Provided no force other thangravity interfered with the cannonball’s motion, itwould continue circling Earth in that orbit.

In essence, this is how the Space Shuttle stays inorbit. The Shuttle is launched on a path that arcsabove Earth so that the Orbiter is traveling parallelto the ground at the right speed. For example, ifthe Shuttle climbs to a 1 60-kilometer-high orbit,it must travel at a speed of about 28,300kilometers per hour to achieve an orbit. At thatspeed and altitude, the Shuttle’s falling path willbe parallel to the curvature of Earth. Because theSpace Shuttle is freefalling around Earth, amicrogravity environment is created that will lastas long as the Shuttle remains in orbit.

This cannonball travels halfway around Earth becauseof the greater charge of black powder used. Thecannonball’s falling path nearly matches the shape ofEarth.

The black powder charge in this final cannon shotpropels the ball at exactly the right speed to cause itto fall entirely around Earth. If the cannon is movedout of the way, the cannonball will continue orbitingEarth.

Page 104: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

99

2.

1.

Procedure:1. Set up your equipment as shown in the picture.

One team member stands above the large balland holds the end of the string. The secondteam member’s job is to move the small ball indifferent ways to answer the followingquestions. Write down your answers whereindicated and draw pictures to show whathappened. Draw the pictures looking straightdown on the two balls.

Orbital DeploymentTeam Members:Around The

World

NorthPole

Equator

1. What path does the satellite (small ball) followwhen it is launched straight out from Earth?

EARTH

Show what happened.

Student Worksheet - 1

Page 105: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

100

2. What path does the satellite follow when it islaunched at different angles from Earth’ssurface?

5. Using the results of your investigation and theinformation contained in the student reader,write a paragraph that explains how satellitesremain in arbit.

Student Worksheet - 2

EARTH

Show what happened.

3. What effect is there from launchingthe satellite at different speeds?

4. What must you do to launch the satellite so itcompletely orbits Earth?

6. Why will the International Space Station be anexcellent place to conduct microgravityresearch?

Page 106: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

101

Objective:

• To demonstrate how mass can bemeasured in microgravity.

Science Standards:Science as InquiryPhysical Science- position and motion of objectsUnifying Concepts and ProcessesChange, Constancy, & Measurement

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataMaking GraphsInterpreting DataControlling Variables

Mathematics Standards:CommunicationNumber & Number RelationshipsComputation & EstimationMeasurement

Activity Management: Before doing this activity, you will need toconstruct enough inertial balances for theentire class. Plan on having one balancefor every three or four students. Exceptfor the empty film canisters, which arefree from photo processors, materials andtools for making all the balances can beobtained at a hardware store wherelumber is also sold. To reduce your cost,buy hacksaw blades in multipacks. Thedimensions for the wood blocks are notcritical and you may be able to find apiece of scrap lumber to meet your needs.The only tools needed to construct thebalances are a crosscut or backsaw to cut

Inertial Balance

Objects of unknown mass are measured with a balance thatworks in microgravity.

the wood into blocks and a coping saw to cut thenotch for insertion of the blade. If you have accessto power tools, use a table scroll saw to cut thenotches. The notches should be just wide enoughfor the hacksaw blade to be slid in. If the notchesare too wide, select a thinner blade for the copingor scroll saw.

MAT

ER

IALS

AN

D T

OO

LS

Hacksaw blade (12 inch)Coping saw (optional)1 C-clamp (optional)Plastic 35mm film canisterTissue paperMasking tapeWood block (1x2.5x4 inch)Wood sawsGlueObjects to be measuredGraph paper, ruler, and pencilPennies and nickelsStopwatch

Page 107: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

102

Cut the blocks, one for each balance, about 10centimeters long. Cut a 2 centimeter deep notchin one end of each block. Slip one end of thehacksaw blade into the notch to check the fit. Itshould be snug. Remove the blade and apply asmall amount of glue to both sides of the end andslip the blade back in place. Make sure the bladeis slightly above and parallel to the bottom flatside of the block. Set the balance aside to dry.

Use tape to attach a film canister to the oppositeend of each balance. Squirt hot glue into thebottom of the canister and drop in a large metal

washer. Repeat two more times. The reason fordoing this is to provide extra mass to the canisterend of the inertial balance. Students will becounting how long it takes the device to oscillatefrom side to side 25 times. A very light canisterwill swing faster than the students can count.Extra mass will slow the device so that countingis possible.

To use the inertial balance, students will place thewood block on the edge of a table

Side View

Insert blade with glue.

Use tape to cover saw teeth.

Tape 35mm film canisterto end of blade.

Cut small notch inwood. Insert andglue end of blade.

12 inch hacksaw blade

6.5 X 2.5X 10 cmwood block

6.5 X 2.5 X 10 cm

Page 108: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

103

so the hacksaw and canister stick over the edge.The balance can be anchored with a clamp or justpressed to the tabletop by one student in theteam. An object of unknown mass is placed in thecanister and the students determine its mass bydeflecting the blade so it swings from side toside. Unknown masses can be such things asnuts and bolts, washers, and pebbles. The tissuepaper called for in the instructions anchors theunknown object in the canister so it will not slosharound and throw off the accuracy.

The first step for students is to calibrate thebalance. This is done with a standard mass suchas a penny. The length of time the balance takesto oscillate 25 times is measured for zero through10 pennies. The results are plotted on a graphWhen an unknown mass is placed in the canister,its time will be measured. By referring to thegraph, students will be able to determine theunknown object’s mass by seeing where it falls onthe graph. The mass will be given in units ofpennies. If desired, the balance can be calibratedin grams by measuring the pennies on a metricbeam balance.

Save the student reader for use after the activity.

Assessment:Collect calibration graphs and data sheets.

Extensions:1. Construct and demonstrate inertia rods. The

instructions follow. The materials list is foundon the next page.

A. Using a saw, cut the PVC tube in half. Smoothout the ends, and check to see that the caps fitthe ends.

B. Squeeze a generous amount of silicone rubbersealant into the end of one of the tubes. Slidethe pipe into the tube. Using the dowel rod,push the pipe to the middle of the tube. Addsealant to the other end of the tube and insert

0 1 2 3 4 5 6 7 8 9 1 0

2 01 91 81 71 61 51 41 31 21 11 0S

ec

on

ds

pe

r 2

5 C

yc

les

N u m b e r o f P e n n i e s

P e n n yN i c k e l

S a m p l e G r a p h

the second pipe. Position both pipes so theyare touching each other and straddling thecenter of the tube.Set the tubeaside to dry.

C. Squeeze sealantinto the ends ofthe second tube.Push the remainingpipes into the ends of the tubes untilthe ends of thepipes are flush with the tube ends. Be surethere is enough compound to cement the pipesin place. Set the tube aside to dry.

D. When the sealant of both tubes is dry, check tosee that the pipes are firmly cemented in place.If not, add additional sealant to complete thecementing. Weigh both rods. If one rod islighter than the other, add small amounts ofsealant to both ends of the lighter rod. Re-weigh. Add more sealant if necessary.

E. Spread some sealant on the inside of the PVCcaps. Slide them onto the ends of the tubes tocement them in place.

F. Use fine sandpaper to clean the rods.

Page 109: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

104

Demonstrate the rods by having a student pick upboth of the rods from their upper ends and tell theclass whether the rods feel the same. Then, thestudent grasps each rod by its middle, extendsarms, and twists the rods side to side as rapidlyas possible. One rod will be easy to twist and theother difficult. The effect is caused by thedistribution of the mass in each rod. Because theends of the rods move more rapidly than themiddle during twisting, the student feels more

inertia in the rods with the masses at the endsthan the rod with the masses in the middle. Relatethis experience to the way the inertial balancesoperate.

2. Ask students to design an inertial balance thatautomatically counts oscillations.

3. Have students enter their calibration data into agraphing calculator and use the calculator todetermine unknown masses when newmeasurement results are entered.

Weight

Weight

Weight

PVC 3/4 in. water tube(about 1.5 to 2 m long)

4 iron pipe nipples (4-6 in. Iongsized to fit inside PVC pipe)

4 PVC caps to fit water pipeSilicone rubber sealantScale or beam balanceSawVery fine sandpaper1/2 in. dowel rodM

ATE

RIA

LS A

ND T

OO

LS

Page 110: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

105

The microgravity environment of an orbitingSpace Shuttle or space station presents manyresearch problems for scientists. One of theseproblems is measurement of mass. On Earth,mass measurement is simple. Samples, such as acrystal, or subjects, such as a laboratory animal,are measured on a scale or beam balance. In ascale, springs are compressed by the object beingmeasured. The amount of compression tells whatthe object’s weight is. (On Earth, weight is relatedto mass. Heavier objects have greater mass.)Beam balances, like a seesaw, measure anunknown mass by comparison to known masses.With both these devices, the force produced byEarth’s gravitational attraction enables them tofunction.

In microgravity, scales and beam balances don’twork. Setting a sample on the pan of a scale willnot cause the scal.e springs to compress. Placinga subject on one side of a beam balance will notaffect the other side. This causes problemsfor researchers. For example, alife science study on the nutritionof astronauts in orbit mayrequire daily monitoring of anastronaut’s mass. In materialsscience research, it may benecessary to determine how themass of a growing crystalchanges daily. How can mass bemeasured without gravity’seffects?

Mass can be measured inmicrogravity by employinginertia. Inertia is the propertyof matter that causes it to resistacceleration. If you have ever

Student Reader - 1

Inertia and Microgravitytried to push anything that is heavy, you knowabout inertia. Imagine trying to push a truck. Youwill quickly realize that the amount of inertia orresistance to acceleration an object has is directlyproportional to the object’s mass. The moremass, the more inertia. By directly measuring anobject’s inertia in microgravity, you are indirectlymeasuring its mass.

The device employed to measure inertia and,thereby, mass is the inertial balance. It is a springdevice that vibrates the subject or sample beingmeasured. The object to be measured is placed inthe sample tray or seat and anchored. Thefrequency of the vibration will vary with the massof the object and the stiffness of the spring (inthis activity, the hacksaw blade). An object withgreater mass will vibrate more slowly than anobject with less mass. The time needed tocomplete a given number of cycles is measured,and the mass of the object is calculated.

Payload Commander Dr. Rhea Seddon is shown using the Body MassMeasurement Device during the Spacelab Life Sciences 2 mission. The deviceuses the property of inertia to determine mass.

Page 111: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

106

Measuring MassWith InertiaCalibrating the Inertial Balance:1. Clamp the inertial balance to the table so the

spring (saw blade) and sample bucket extendsover the edge of the table.

2. Pick one member of your team to be thetimekeeper, another to record data, andanother to count cycles. Refer to the box to theright for details on how to perform each task.

3. Begin calibration by inserting a wad of tissuepaper in the bucket and deflecting the spring.Release the bucket and start counting cycles.When the time for 25 cycles is completed,enter the number in the data chart and plot thepoint on the graph for zero pennies. Toimprove accuracy, repeat the measurementsseveral times and average the results.

4. Insert 1 penny into the bucket next to the tissuepaper wad and measure the time it takes for 25cycles. Record the data as 1 penny.

5. Repeat the procedure for 2 through 10 penniesand record the data.

Student Work Sheet - 1

Counter: Pull the sample bucket a fewcentimeters to one side and release it. At themoment of release, say “Now” and begincounting cycles. A cycle is completed when thesample bucket starts on one side, swings acrossto the other and then returns to its starting point.When 25 cycles are complete, say “Stop.”

Timer: Time the number of cycles being countedto the nearest tenth of a second. Start timingwhen the counter says “Now” and stop when thecounter says “Stop.”

Recorder: Record the time for 25 cycles asprovided to you by the timer. There will be 11measurements. Plot the measurements on thegraph and draw a line connecting the points.

6. Draw a line that goes through or close to allpoints on the graph. Your inertial balance iscalibrated.

Using the Inertial Balance:1. Place an unknown object in the inertial balance

bucket. Remember to use the same tissuepaper for stuffing. Measure the time for 25cycles. And record your answer.

2. Starting on the left side of the graph, find thenumber of seconds you measured in step 1.Slide straight over to the right until you reachthe graph line you drew in the previous activity.From this intersection point, go straight downto the penny line. This will tell you the mass ofthe unknown object in penny weights.

Page 112: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

107

Measuring MassWith Inertia

Student Work Sheet - 2

Measurement Team:

0 1 2 3 4 5 6 7 8 9 1 0

2 01 91 81 71 61 51 41 31 21 11 0S

ec

on

ds

pe

r 2

5 C

yc

les

N u m b e r o f P e n n i e s

Calibration Graph

Unknown Object 1Mass: __________________ pw

Unknown Object 2Mass: __________________ pw

Unknown Object 3Mass: __________________ pw

Unknown Object 4Mass: __________________ pw

Page 113: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

108

Questions:

1. Will this technique for measuring mass work in microgravity? Yes______ No______Explain your answer:

2. Why was it necessary to use tissue paper for stuffing?

3. How could you convert the penny weight measurements into grams?

4. Would the length of the hacksaw blade make a difference in the results?

5. What are some of the possible sources of error in measuring the cycles?

6. What does a straight line in the calibration graph imply?

Student Work Sheet - 3

Page 114: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

109

Objective:

• To study gravity-driven fluid flow thatis caused by differences in solutiondensity.

Science Standards:Science as InquiryPhysical Science- position and motion of objects- properties of Objects and MaterialsUnifying Concepts and ProcessesChange, Constancy, & MeasurementScience and Technology- abilities of technological design

Science Process Skills:ObservingCommunicatingCollecting DataInferringHypothesizingInterpreting DataControlling VariabiesI nvestigating

Activity Management:In this activity, students combine liquidsof different densities to observe the fluidflow caused by gravity-driven buoyancyand settling. The activity is best done instudent groups of two or three. It canalso be done as a demonstration for theentire class. In this case, obtain anoverhead projector and place beakers onthe lighted stage. The light from belowwill illuminate the contents of the jars tomake them easily visible from across theroom. To reduce distraction, cover theprojector lens to prevent blurry imagesfrom falling on the wall or screen behind.Caution: Be careful not to spill liquid onthe projector.

Gravity-Driven Fluid Flow

Water of different densities is mixed to producegravity-driven fluid flow.

If using this as an activity, provide each studentgroup with a set of materials. Salt canisters, foodcoloring dispensers, and measuring cups can beshared among groups. The materials list calls forglass beakers or tall drinking glasses. Othercontainers can be substituted such as mason jarsor plastic jars like those in which peanut butter issold.

MAT

ER

IALS

AN

D T

OO

LS

2 large (500 ml) glass beakersor tall drinking glasses

2 small (5 to 10 ml) glass vialsThreadFood coloringSaltSpoon or stirring rodMeasuring cup (1/4 cup)WaterPaper towels

Page 115: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

110

The vials are available from school science supplycatalogs for a few dollars per dozen. Choose glassvials with screw tops and a capacity of 3 to 4 ml.Small cologne sample bottles can be substitutedfor the vials. It is important that the vials orbottles are not too large because the process oflowering large containers into the beakers can stirup the water too much. It is recommended you tiethe string around the neck of the vial yourself tomake sure there is no slippage.

The student instructions ask the students toconduct three different experiments. In the first,the effects of saltwater and freshwater areinvestigated. In the second, the effects of warmand cold water are investigated. The thirdexperiment is an opportunity for students toselect their own materials. They might try mixingoil and vinegar, sugar and saltwater, or oil andwater. It may be necessary for the thirdexperiment to be conducted on another day whilethe new materials are collected.

Give each student group at least one set ofinstructions and two data sheets. Save thestudent reader for use after the experiment.

Assessment:Discuss the experiment results to determinewhether the students understand the concepts ofbuoyancy and sedimentation. Collect the studentpages for assessment of the activity.

Extensions:1. How could this experiment be conducted if it

were not possible to use food coloring for amarker? (In experiments where the density ofthe two fluids is very close, the addition offood coloring to one fluid could alter theresults.)

2. Design an apparatus that can be used tocombine different fluids for experiments on thefuture International Space Station.

3. Design an experiment apparatus that wouldpermit the user to control the buoyancy andsedimentation rates in the beakers.

4. Design an experiment to measure the gravity-driven effects on different fluids in which thefluids are actually gases.

Page 116: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

111

Gravity is an important force at work in themovement of fluids. Fluids can be liquids orgases. The important thing about fluids is theycan flow from place to placeand can take the shape of thecontainer they are in.

When you pour a liquid fromone container into another,gravity is the driving force thataccomplishes the transfer.Gravity also affects fluids “atrest” in a container. Add asmall amount of heat to thebottom of the container andthe fluid at the bottom beginsto rise. The heated fluidexpands slightly and becomesless dense. In other words, thefluid becomes buoyant. Coolerfluid near the top of the container is more denseand falls or sinks to the bottom.

Many crystals grow in solutions of differentcompounds. For example, crystals of salt grow inconcentrated solutions of salt dissolved in water.In the crystal growth process, the ions that makeup the salt come out of solution and are depositedon the crystal to make it larger. When thishappens, the solution that held the moleculebecomes a little less salty than it was a moment

Student Reader - 1

Gravity-Driven Fluid Flow

ago. Consequently, the density of the solution is alittle bit less than it was. This, in turn, causes afluid flow in the solution. The slightly less salty

solution is buoyant and risesto the top of the containerwhile saltier, or more dense,solution moves in to take itsplace.

Scientists are interested ingravity-driven fluid flowsbecause they have learnedthat these flows, whenoccurring during the growthof crystals, can create subtlechanges in the finishedcrystals. Flaws, called defects,are produced that can alter theway those crystals perform invarious applications. Crystals

are used in many electronic applications, such asin computers and lasers.

To learn how to grow improved crystals on Earth,scientists have been growing crystals in themicrogravity environment of Earth orbit.Microgravity virtually eliminates gravity-drivenfluid flows and often produces crystals ofsuperior quality to those grown on Earth. One ofthe major areas of materials science research onthe International Space Station will involve crystalgrowth.

Dyed freshwater in saltwater beaker

Page 117: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

112

Procedure1. Fill the first beaker with freshwater and set it on

the lab surface. Also fill the second beaker withfreshwater. Into the second beaker addapproximately 50 to 100 grams of salt. Stir thewater until the salt is dissolved.

2. Dip the first small glass vial into the beakerwith freshwater. Fill it nearly to the top. Add acouple of drops of food coloring to the water inthe vial. Close the top of the vial with yourthumb and shake the water until the foodcoloring is mixed throughout. Place this vialnext to the saltwater beaker.

3. Partially fill a second vial with salty water andfood coloring. After mixing, place it in front ofthe beaker filled with freshwater.

4. Wait a few minutes until the water in the twobeakers is still. Gently lift one of the vials bythe string and slowly lower it into the beakernext to it. Let the vial rest on its side on thebottom of the beaker and drape the string overthe side as shown in the pictures. Answer thequestions on the data sheets and sketch whatyou observed in the diagrams.

5. Place the second vial in the other beaker asbefore. Make your observations, sketch whatyou observed, and answer the questions aboutthe data.

Student Work Sheet - 1

Gravity-Driven Fluid Flow

Second Experiment Procedure:1. Empty the two beakers and rinse them

thoroughly.2. Fill one beaker with cold water and the other

with warm water.3. Repeat steps 2 through 5 in the previous

experiments.

Original Experiment:1. On a blank sheet of paper, write a proposal for

an experiment of your own design that usesdifferent materials in the beakers. Include inyour proposal an experiment hypothesis, amaterials list, and the steps you will follow toconduct your experiment and collect data.Submit your experiment to your teacher forreview.

2. If your experiment is accepted for testing,• gather your materials• conduct the experiment• submit a report summarizing your observations and conclusions

Page 118: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

113

Research Team Members:

Gravity-Driven Fluid FlowData Sheet

Student Work Sheet - 2

Beaker and Vial:1. Water in beaker (check one)

Fresh _____Salty _____

2. Water in vial (check one)Fresh _____Salty _____

3. Describe and explain what happened

Sketch what happened.

Sketch what happened.

Beaker and Vial:1. Water in beaker (check one)

Fresh _____Salty _____

2. Water in vial (check one)Fresh _____Salty _____

3. Describe and explain what happened

Page 119: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

114

Objective:

• To study surface tension and the fluidflows caused by differences insurface tension.

Science Standards:Science as InquiryPhysical Science- position and motion of objects- properties of objects and materialsUnifying concepts and processesChange, Constancy, &Measurement- evidence, models, & exploration

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataInferringPredictingInterpreting DataInvestigating

Activity Management:The purpose of this activity is todemonstrate how surface tensionchanges can cause fluids to flow. Itrequires shallow trays with raised edgessuch as cafeteria trays. Large Styrofoamfood trays from a supermarket can alsobe used, but they should be the kindwith a smooth surface and not a waffletexture. Light-colored trays make abetter background for seeing thesurface tension effects. Encouragestudents to try different mazes andinvestigate the effects of wide versusnarrow mazes.

Surface Tension-Driven Flow

A clay maze is constructed on a cafeteria tray. Wateris added. A drop of liquid soap disrupts the surfacetension of the water and creates currents that aremade visible with food coloring.

Cafeteria tray (with raised edge)Plasticine modeling clayWaterLiquid soapFood coloringToothpickPaper towelsBucket or basin for waste waterM

ATE

RIA

LS A

ND T

OO

LS

Water handling will be a bit of a problem. After adrop of liquid soap is applied to the water, thewater must be discarded and replaced beforetrying the activity again. Carrying shallow water-filled trays to a sink could be messy. Instead, it isrecommended that a bucket or large waste basketbe brought to the trays so the trays can beemptied right at the workstation.

Page 120: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

115

When soap is applied to the water, food coloringat the water’s surface will be driven along themaze by the disruption of the water’s surfacetension. Make sure students observe whathappens to the water at the bottom of the tray aswell. A reverse current flows along the bottom tofill in for the water that was driven along thesurface.

Save the student reader for use after the activity.

Assessment:Conduct a class discussion to ensure the studentsunderstand that variations in surface tension in afluid cause fluid flow. Collect the student pages.

Extensions:1. Demonstrate additional surface tension effects

by shaking black pepper into aglass of water. Because of surfacetension, the pepper will float. When a drop ofsoap is added to the water, the pepper willsink. This same effect can be seen in a broaderview by placing water into a petri dish andadding pepper ancl then soap. The pepper willbe driven to the sides of the dish whereparticles will start sinking. The petri dishexperiment can be done as a demonstrationwith an overhead projector.

2. Make a surface tension-propelled paper boat bycutting a small piece of paper in the shapeshown to the right and floating it on cleanwater. Touch a small amount of detergent tothe water in the hole at the back of the boat.

3. Design an experiment to test whether thetemperature of a liquid has any effect onsurface tension.

4. Try floating needles on water and observe whathappens when detergent is added. To float theneedle, gently lower it to the water’s surfacewith a pair of tweezers.

Surface Tension Paper Boat(actual size)

Page 121: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

116

If you have ever looked closely at drops of water,you will know that drops try to form sphericalshapes. Because of gravity’s attraction, drops thatcling to an eye dropper, for example, arestretched out. However, when the drops fall theybecome spherical.

Student Reader - 1

Surface Tension

The shape of a water drop is a result of surfacetension. Water is composed of moleculesconsisting of two hydrogen atoms and one atomof oxygen. These molecules attract each other. Inthe middle of a drop of water, molecules attracteach other in all directions so no direction ispreferred. On the surface, however, molecules areattracted across the surface and inward. Thiscauses the water to try to pull itself into a shapethat has the least surface area possible-thesphere. Because of gravity, drops resting on asurface, like water drops on a well-waxed car,flatten out somewhat like the figure above.

The molecules on the surface of a liquid behavelike an elastic membrane.You can easily see theelastic membrane effect by floating a needle onthe surface of a glass of water. Gently lower theneedle to the water surface with a pair oftweezers. Examine the water near the needle andyou will observe that it is depressed slightly asthough it were a thin sheet of rubber.

The addition of a surfactant, such as liquid soap,to water reduces its surface tension. Watermolecules do not bond as strongly with soapmolecules as they do with themselves. Therefore,the bonding force that enables the molecules tobehave like an elastic membrane is weaker. If youput a drop of liquid soap in the glass with theneedle, the surface tension is greatly reduced andthe needle quickly sinks. When you added liquidsoap to the water in the experiment, the surfacetension was weakened in one place. The water onthe surface immediately began spreading awayfrom the site of the soap. The clay wallschanneled the flow in one direction. To make upfor the water moving away from the site wherethe soap was added, a second water currentformed in the opposite direction along the bottomof the tray.

Page 122: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

117

Because a microgravity environment greatlyreduces buoyancy-driven fluid flows andsedimentation, surface tension flows becomevery important. Microgravity actually makes iteasier to study surface tension-driven flows. OnEarth, studying surface tension in the midst ofgravity-driven flows is like trying to listen to awhisper during a rock concert. The importanceof surface tension research in microgravity isthat surface tension-driven flows can interferewith experiments involving fluids. For example,crystals growing on the International Space

Student Reader - 2

Car Surface

Air

Molecules inside a water drop are attracted in all directions. Drops on the surfaceare attracted to the sides and inward.

Station could be affected by surface tension-driven flows, leading to defects in the crystalstructure produced. Understanding surfacetension better could lead to new materialsprocessing techniques that either reduce surfacetension’s influence or take advantage of it. Oneexample of a positive application of surfacetension is the use of sprayers to paint a surface.Surface tension causes paint to form very smalldroplets that cover a surface uniformly withoutforming drips and runs.

Page 123: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

118

Team Members:

Surface Tension-Driven Flows

Student Work Sheet - 1

Setup Instructions:1. Roll clay into long “worms” 1 to 2 centimeters

in diameter. Lay the worms out on the tray toproduce a narrow valley about 3 to 4centimeters wide that is closed on one end.Squeeze the worms so they stick to the trayand form thin walls.

2. Add water to the tray until it almost reaches thetops of the maze walls. Let the water settlebefore the next step.

3. Add a drop of food coloring to the maze nearits end. Drop the coloring from a height ofabout 5 centimeters so that some of the foodcoloring spreads out slightly on the surfacewhile the rest sinks to the bottom.

4. Dip the toothpick in the liquid soap and touchthe end of the toothpick to the water at the endof the maze beyond the dye. Observe whathappens.

5. Try a different maze to see how far you can getthe dye to travel.

Questions:1. Why did the surface water move?

2. Did water near the bottom move as well?If it moved, why ?

Make a sketch of the clay maze youconstructed. Use arrows to show thedirection of surface water movementafter you added the soap. Use dashedline arrows to indicate the direction ofany subsurface currents.

Page 124: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

119

Objective:

• To investigate the effects oftemperature on the surface tension ofa thin liquid.

Science Standards:Science as InquiryPhysical Science- position and motion of objects- properties of objects and materialsUnifying Concepts and ProcessesChange, Constancy, & Measurement

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataInferringPredictingInterpreting DataControlling VariablesInvestigating

Activity Management:This experiment can be done as astudent activity or a classroomdemonstration for small groups ofstudents. If done as a demonstration,it can be set up while students areconducting the Surface Tension-DrivenFlows activity. Rotate small groupsthrough the demonstration.

Be sure to use Pyrex® petri dishes forthe demonstration. Also provide eyeprotection for yourself and thestudents. It is important that tehheating surface of the hot plate be

Temperature Effects onSurface Tension

A thin pool of liquid heated from below exhibits polygonalcell structure due to surface tension-driven flows.

Cooking oilPowdered cinnamonTwo Pyrex® petri dishes and

coversLaboratory hot plateHeat-resistant gloves, hotpad, or

tongsIce cubesEye protectionM

ATE

RIA

LS A

ND T

OO

LS

level. Otherwise, it will be necessary to add moreoil to cover the bottom of the petri dish. A thinlayer of oil is essential to the success of theexperiment. Thin layers, on the order of 1 or 2millimeter, do not exhibit significant convectioncurrents as do layers that are much thicker. Theresimply is not enough room for convectioncurrents to develop in thin layers. Heat isconducted through the thin layer to the surfacevery quickly. Since the lower and upper parts of

Page 125: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

120

the liquid are at nearly the same temperature, noconvection currents develop.

The demonstration is conducted with two petridishes. Use the lids of both dishes for holding theoil and spice. To see the surface tension effects,sprinkle the cinnamon from a height of 20 or 30centimeters to help it spread out evenly on thesurface of the oil.

Place the first dish on the hot plate and observethat patterns are produced by the cinnamon.Before placing the second dish lid on the hotplate, invert and insert the bottom of the seconddish into the lid. This will effectively place all theoil in contact with glass so there is not anyexposed oil surface. The reason for the twodifferent runs of the demonstration is to verifywhether or not buoyancy-driven convectioncurrents are involved in moving the cinnamonmarkers. If these currents are at work, thecinnamon will spread out and swirl through theoil. In other words, the second part of thedemonstration is a control for the first part.

Assessment:Conduct a class discussion on why it is importantfor microgravity scientists to understand aboutsurface tension. Coilect the student pages.

Extensions:1. Experiment with other fluid and marker

combinations. Several microgravityexperiments in space have used 10 centistokesilicone oil (dimethylpolysiloxane) withpowdered aluminum as a marker. Bothchemicals are available from chemical supplycatalogs. The demonstration works best if thealuminum is more flaky than powder.Aluminum flakes will provide reflectivesurfaces that intensify the optical effect. Youcan make your own aluminum flakes byobtaining flat enamel hobby paint and allowingthe aluminum flakes to settle to the bottom ofthe bottle. Pour off the fluid and wash thesediment several times with nail polishremover and let dry.

2. Videotape the convective flow patterns and piaythem back at different speeds to see moredetails on how surface tensiondriven flowsdevelop.

3. Look for patterns in nature, such as mudcracks, that are similar to the patterns seen inthis activity. Are nature’s patterns produced inthe same way or by some differentmechanism?

Page 126: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

121

Around the turn of this century, physicist HenriBenard discovered that liquid in thin pools heatedfrom below quickly forms flow patternsconsisting of polygonal cells. He made thisdiscovery by placing tiny markers in the fluid thatshowed how the fluid moved. The cells resembledthose that form due to convection currents whena pot of soup is heated. The interesting thingabout Benard’s discovery is that buoyancy-drivenconvection currents were not responsible for theflow that was produced.

When a thick pool of liquid is heated from below,liquid at the bottom expands and becomes lessdense. Because of buoyancy, the less dense liquidrises to the top of the pool where it spreads out.Cooler surrounding liquid moves in to take theplace of the warmer fluid that rose to the top. Thisliquid heats up, becomes less dense, and alsorises to the top to create a cycle that continues aslong as heat is applied. This cycling is called abuoyancy-driven convection current.

The problem with studying fluid flows in a heatingpot of soup is that convection currents appear tobe the only force at work. Actually, surfacetension flows are also present but, because theyare of lower intensity, they are masked by themore violent buoyancy-driven convectioncurrents. By creating a very thin liquid pool(about 1 mm or thinner), Bénard was able to

eliminate buoyancy-driven convection. In verythin liquids there just is not enough verticaldistance for significant buoyancydrivenconvection currents to get started. The fluid flowBenard observed was produced by changes insurface tension.

In the cooking oil experiment, you observed twopetri dishes with a thin layer of oil and powderedcinnamon markers. The uncovered dish, whenheated from below, began forming circular cellsthat eventually grew into each other to producepolygonal cells. Heat from hot spots in the hotplate was quickly conducted to the surface of theoil. The increase in temperature of the oil reducedthe surface tension in those locations. Thisreduction was apparent because the oil flowedfrom the center of the hot spots in all directionsto the outside. Compare this action to whathappened when a drop of liquid soap wastouched to the surface of a tray of water in theprevious activity. In the second petri dish, a layerof glass was placed over the thin oil layer so theoil did not have an exposed surface. In thismanner, surface tension effects were eliminated.No fluid flows were observed, meaning that

Student Reader - 1

TemperatureEffects on

SurfaceTension

Polygonal cells produced in a thin pool of liquid heatedfrom below.

Page 127: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

122

buoyancy-driven convection was not at work. Thisdemonstration served as a scientific control forthe first experiment.

In fluid physics experiments aboard the SpaceShuttle and the International Space Station,buoyancy is practically eliminated because ofmicrogravity. Surface tension, however, becomesan important force because it is not a gravity

Student Reader - 2

dependent phenomenon. In crystal growing andother fluid physics experiments, surfacetensiondriven flows can affect the outcome. Forthis reason, scientists are trying to understandthe mechanics of surface tension-driven flows inmicrogravity.

In these two diagrams, the difference betweenbuoyancy-driven convection currents (left) andsurface tension-driven convection currents (right) isshown. Flow in the left diagram is produced bychanges in fluid density brought about by heating thebottom. Flow in the right diagram is brought about byreducing surface tension above a heated plate.

Heated Plate

Cooler SurfaceFlow

Flow

Warm Fluid

Cool Fluid

Thick Liquid Pool

Heated Plate

Cooler Surface

CoolCool Warm

Thin Liquid Pool

Magnified view of the polygonal cells that are produced by surfacetensiondriven convection.

Page 128: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

123

Name: _____________________________

1. Sketch the fluid flow patterns thatappeared in the thin pool of cooking oilwhen heat was applied to the bottom ofthe first petri dish. Indicate with arrowswhich direction(s) the fluid flowed.

Student Work Sheet - 1

Temperature Effects on Surface Tension

What effect did an increase in temperaturehave on the surface tension of the oil?

Why?

2. Sketch the fluid flow patterns thatappeared when heat was applied to thebottom of the second petri dish. Indicatewith arrows the direction(s) of any fluidflows observed.

Explain what you observed.

What effect on surface tension do youpredict lowering the temperature of the oilwould have? How could this be observed?

Page 129: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

124

Objective:

• To investigate the effect of gravityon the burning rate of candles.

Science Standards:Science as InquiryPhysical Science- properties of objects & materialsUnifying Concepts & ProcessesChange, Constancy, &

Measurement

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataInferringHypothesizingPredictingInvestigating

Mathematics Standards:Measurement

Activity Management:This activity serves as an introductionto the candle drop activity that follows.In both activities, students areorganized into cooperative learninggroups of three. It may be useful tokeep the same groups together forboth activities.

The objective of this activity is toobserve candle flame properties andprepare students to makeobservations of candle flames inmicrogravity where observingconditions are more difficult. Before

Candle Flames

The burning rate and other properties of candleflames are investigated.

MAT

ER

IALS

AN

D T

OO

LS

Birthday candles (2 per group)MatchesBalance beam scale (0.1 gm or

greater sensitivity)Clock with second hand or

stopwatchWire cutter/pliersWire (florist or craft)20 cm square of aluminum foilEye protection

letting students start the activity, conduct adiscussion on the different observations they canmake. Make a list of terms that can be used todescribe flame shape, size, color, and brightness.

At the end of the experirnent, student groups areasked to write a hypothesis to explain thedifferences observed in the burning of the twocandles. It may be helpful to discuss hypothesis

Page 130: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

125

writing before they get to that part. Thehypotheses should relate to gravity-inducedeffects. In the case of candle 2, the wax of thecandle is above the flame. Convection currents (agravity-driven phenomenon) deliver lots of heat tothe candle which causes more rapid melting thanoccurs with candle 1. Much of that wax quicklydrips off the candle (gravity pulls the wax off) somore wick is exposed and the candle burns faster.

The wire used in this activity is a lightweight wireof the kind used by florists and in craft work. Youcan find this wire in craft and hardware stores. Donot use wire with plastic insulation. The flame ofthe candle tipped at an angle of 70 degrees mayreach the wire and begin burning the insulation.Each group will need two wires about 20centimeters long. Precut the aluminum foil into20 centimeter squares. One square is needed foreach group.

Provide each group with one set of studentsheets. Save the student reader for use after theactivity has been completed.

Assessment:Discuss student observations of the candleburning and their hypotheses. Collect the studentwork sheets for assessment.

Extensions:1. Burn a horizontally held candle for one minute.

Weigh the candle before lighting it. As it burns,record the colors, size, and shape of the candleflame. Weigh the candle again and calculatehow much mass was lost.

2. Repeat the above experiments with the candlesinside a large sealed jar. Let the candles burnto completion. Record the time it takes eachcandle to burn. Determine how and why theburning rate changed.

3. Burn two candles which are closetogether. Record the burning rate andweigh the candles. Is the burning ratefaster or slower than each candle alone?Why?

4. Investigate convection currents with aconvection current demonstration apparatusthat is obtained from science supply catalogs,or construct the apparatus as shown below.

5. Obtain a copy of Michael Faraday’s book, TheChemical History of a Candle, and do theexperiments described. (See reference list.)

Wooden box with glassfront. Hold glass onwith tape. Open tapeto light candle.

Chimneymade fromglass, foodcans, or pipe.

Light the end ofpaper wad and thenblow out. Smokewill be drawn intochamber.

Page 131: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

126

Candles are useful for illustrating the complicatedphysical and chemical processes that take placeduring combustion. The candle flame surfaceitself is the place where fuel (wax vapor) andoxygen mix and burn at high temperatures,radiating heat and light. Heat from the flame isconducted down the wick and melts the wax atthe wick base. The liquid wax rises up the wickbecause of capillary action. As the liquid waxnears the flame, the flame’s heat causes it tovaporize. The vapors are drawn into the flamewhere they ignite. The heat produced melts morewax, and so on.

Student Reader - 1

Candle FlamesFresh oxygen from the surrounding air is drawninto the flame primarily because of convectioncurrents that are created by the released heat. Hotgases produced during burning are less densethan the cooler surrounding air. They rise upwardand, in doing so, draw the surrounding air,containing fresh oxygen, into the flame. Solidparticles of soot, that form in the region betweenthe wick and flame, are also carried upward bythe convection currents. They ignite and form thebright yellow tip of the flame. The upward flow ofhot gases causes the flame to stretch out in ateardrop shape.

Dark RedBrown1,000 Co

Light Yellow1,200 Co

White1,400 Co

Orange800 Co

Blue

LuminousZone(Carbonluminescesand burns)

MainReactionZone

Primary(Initial)ReactionZone(Carbon particles)

2O

oDead Space600 C

2 2H O, CO(Unburnedcarbon)

22H O

COOHC2

2O

Candle Flame Reaction Zones,Emissions, and Temperature

Convection

RadiationRadiation

Conduction

Candle Flame Energy Flow

Candle flame diagrams adapted from "The Science of Flames" poster,National Energy Foundation, Salt Lake City, UT.

Page 132: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

127

Candle Flame ResearchTeam Members:

Student Work Sheet - 1

Candle Flames

Procedure:

1. Make a wire stand for each candle so that itlooks like the picture below.

2. Weigh each candle by standing it on a balancebeam scale and recording its weight in gramson the chart on the next page.

3. Put on eye protection.

4. Place candle 1 on the aluminum square. Lightthe candle and let it burn for 1 minute. While itis burning, observe what is happening andwrite your observations below.

70 o

Candle 2

Candle 1

Draw a life-size picture of the candle flame.

Weigh candle 1 again and record its massin the chart.

Page 133: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

128

5. Place candle 2 on the aluminum square. Lightthe candle and let it burn for 1 minute. While itis burning, observe what is happening andwrite your observations below.

Student Work Sheet - 2

Draw a life-size picture of the candle flame.

Weigh candle 2 again and record its mass inthe table.

Calculate the difference in mass for each candleand enter your answers in the table.

Candle Mass Table

Beforeburningmass

Afterburningmass

Difference

1 2

Summarize your observations below.

Write a hypothesis for how you think a candle willburn in microgravity.

Page 134: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

129

Objective:

• To observe candle flame propertiesin freefall.

Science Standards:Science as InquiryPhysical Science- position and motion of objectsUnifying Concepts & ProcessesChange, Constancy, & MeasurementScience &Technology- abilities of technological design

Science Process Skills:ObservingCommunicatingCollecting DataInferringPredictingInterpreting DataHypothesizingControlling VariablesInvestigating

Activity Management:Before attempting this activity, be sureto conduct the Candle Flames activity.Doing so will sharpen the observationskills of the students. This is importantbecause, in this activity, students willbe observing the size, shape, and colorof a candle flame as it is falling.

Investigating candle flames inmicrogravity can be done as either ademonstration or an activity. If used asa demonstration, only one candle dropjar is necessary. If used as an activity,one candle drop jar is needed for eachstudent group. Clear plastic foodstorage jars are available at variety

Candle Flame in Microgravity

stores, but plastic peanut butter jars will work aswell. The jars should be 1 quart or half gallon size(3 pound size if peanut butter jars are used). Theoxygen supply in smaller jars runs out too quicklyfor proper observations.

The wood block and screws called for in thematerials and tools list can be replaced with alump of clay. Press the lump to the inside of the

A burning candle is encased by a clear plastic jar anddropped for a study of flames in microgravity.

MAT

ER

IALS

AN

D T

OO

LS

Clear plastic jar and lid (2 litervolume)*

Wood blockScrewsBirthday candlesMatchesDrill and bitVideo camera and monitor

(optional)Eye protection* Empty 3-lb plastic peanut

butter jar can be used.

Page 135: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

130

jar lid and push the end of the candle into theclay. It will probably be necessary to reform and/or reposition the clay after a couple of drops. Thewood block and screws make a longlasting candledrop jar.

If you are using wood blocks and screws, preparethe candle drop jars by drilling a hole in the centerof the block to hold the end of the candle. Drilltwo pilot holes into the wood for the screws.Finally, drill holes through the plastic jar lid. Withthe block in place, insert screws through the lidholes and screw them into the wood block whereyou drilled the pilot holes. The candle drop jar isready.

If you are using this as an activity, divide studentsinto groups of three. Save the student reader foruse after the experiment has been conducted.Students will drop the candle at least three timesduring their investigation. During the drops, thereare three jobs that must be performed. Onestudent will drop the candle, another will catch it,and the third will observe the properties of thecandle flame as it falls. The jobs should be rotatedthrough the group so each student performs eachjob once.

Since fire is used, be sure everyone working withthe activity wears eye protection. The activityworks best in a room that can be darkened.Coordinate the observations of the studentgroups so all are ready to drop the candle whenthe lights are dimmed.

Students will observe that the first time a birthdaycandle is lit, the flame is larger than when it is litagain. This happens because the wick sticks outfarther from the wax on a new candle than it doeson a used candle. The excess is burned quicklyand the flame size diminishes slightly.

Assessment:Use the student pages for assessment. Foradditional work, have students actually build amodel of the microgravity experiment they areinstructed to design in the last step on the studentpages. The students can present their ideas to therest of the class and exhibit their device.

Extensions:1. If videotape equipment is available, videotape

the candle flame during the drop. Use thepause control during the playback to examinethe flame shape.

2. If a balcony is available, drop the jar from agreater distance than is possible in aclassroom. Does the candle continue to burnthrough the entire drop? For longer drops, it isrecommended that a catch basin be used tocatch the jar. Fill up a large box or plastic trashcan with Styrofoam packing material or looselycrumpled plastic bags or newspaper.

Page 136: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

131

Microgravity experiments using drop towers andSpace Shuttle Orbiters have provided scientistsvaluable insights on how things burn. In thetypical experiment, a flammable material, such asa candle, is ignited by a hot wire. The ignition andcombustion process is recorded by moviecameras and other data collection devices. Usingthese devices, scientists have learned there aresignificant differences between fires on Earth innormal gravity and those in microgravity.

The sequence of pictures, at the bottom of thispage, illustrates a combustion experimentconducted at the NASA Lewis Research Center132 Meter Drop Tower. These pictures of a candle

Student Reader - 1

Candle Flames in Microgravityflame were recorded during a 5-second droptower test. An electrically heated wire was used toignite the candle and then withdrawn 1 secondinto the drop. As the pictures illustrate, the flamestabilizes quickly, and its shape appears to beconstant throughout the remainder of the drop.Instead of the typical teardrop shape seen onEarth, the microgravity flams becomes spherical.On Earth, the flame is drawn into a tip by therising hot gases. However, convection currentsare greatly reduced in microgravity. Fresh oxygenis not being delivered to the candle by thesecurrents. Instead, oxygen works it way slowly tothe flame by the process of diffusion. Soon, theflame temperature begins to drop because the

Candle flame test in the 132 Meter Drop Tower at the NASA Lewis Research Center

Page 137: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

132

combustion is less vigorous. The lowertemperature slows down the melting andvaporization of the candle wax. Candles onboardthe first United States Microgravity Laboratory,launched in June 1992, burned from 45 secondsto about 1 minute before being extinguishedbecause of the dropping temperature andreduction of wax vapor.

Combustion studies in microgravity areimportant to spacecraft safety. Unlike house fireson Earth, you can not run outside of a spacestation and wait for the fire department to arrive.Fires have to be extinguished quickly and safely.To do this it is essential to understand how firesare ignited in microgravity and how they spread.The goal is to make sure that a fire never getsstarted.

In the absence of buoyancy-driven convection, asin microgravity, the supply of oxygen and fuelvapor to the flame is controlled by the muchslower process of molecular diffusion. Wherethere is no “up” or “down,” the flame tendstoward sphericity. Heat lost to the top of thecandle causes the base of the flame to bequenched, and only a portion of the sphere isseen. The diminished supply of oxygen and fuelcauses the flame temperature to be lowered to thepoint that little or no soot forms. It also causesthe flame to anchor far from the wick, so that theburning rate (the amount of wax consumed perunit time) is reduced.

Student Reader - 2

Page 138: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

133

Candle Drop Team Members:

Candle DropStudent Sheet - 1

Procedure:1. Put on eye protection.

2. Light the candle and screw the jar on to the lid.Observe the candle until it goes out.

3. Draw a picture of the shape of the candle flamebelow.

What is the color of the flame?

Predict what you think will happen to thecandle flame when the candle is dropped.

4. Open the jar to release the bad air. Relight thecandle and screw the jar back on to the lid.Have one team member hold the jar as high offthe floor as possible. On the count of three, thejar is dropped to the floor where a secondteam member is waiting to catch it. The thirdmember acts as the observer. Data arerecorded by the observer in the table on thenext page.

5. Repeat step 4 twice more but rotate the jobs soeach team member gets the chance to drop thejar, catch the jar, and write down observations.

Page 139: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

134

Team Member: 1 2 3

Candle flame shape

Candle flame brightness

Candle flame color

Other observations

Candle Drop Data Table

Student Sheet - 2

What changes took place when the candle flame experienced microgravity?

Compare these changes to the candle flame that was not dropped.

Why do you think these changes took place?

Design a candle flame experiment that could be used on the International Space Station. Write out, onanother piece of paper, the experiment hypothesis and sketch the apparatus that will be needed. Writea short paragraph describing the device, how it will work, and what safety procedures you would use.

Page 140: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

135

Objective:

• To demonstrate how atoms in asolid arrange themselves.

Science Standards:Science as InquiryPhysical Science- position and motion of objectsUnifying Concepts & ProcessesChange, Constancy, &

MeasurementScience & Technology- abilities of technological design

Science Process Skills:ObservingCommunicatingCollecting DataInferringPredictingInterpreting DataHypothesizingControlling VariablesI nvestigating

Activity Management:The crystal model device describedhere is best suited for use as aclassroom demonstration. It is avibrating platform that illustrates intwo dimensions the development ofcrystal structure and defectformation. BBs, representing atomsof one kind, are placed into a shallowpan which is vibrated at differentspeeds. The amount of vibration atany one time represents the heatenergy contained in the atoms.Increasing the vibration ratesimulates heating of a solid material.

Crystallization Model

on

off

BBs on a vibrating plafform arrange themselves in patternssimilar to the atoms in solids.

Wood base and supportsShallow pan3 Small bungee cordsSmall turnbuckleSurplus 1 10 volt AC electric

motorMotor shaft collarVariable power transformerSeveral hundred BBsHook and loop tapeM

ATE

RIA

LS A

ND T

OO

LS

Eventually, the atoms begin to separate and movechaotically. This simulates melting. Reducing theamount of vibration brings theatoms backtogether where they “bond” with each other. Inthis demonstration, gravity pulls the BBs togetherto simulate chemical bonds. By observing themovement of BBs, a number of crystal defectscan be studied as they form and transform.Because of movements in the pan, defects cancombine (annihilation) in such a way that theideal hexagonal structure is achieved and newdefects form.

Page 141: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

136

The model is viewed best with small groups ofstudents standing around the device. After thesolid “melts,” diminish the motor speed graduallyto see the ways the atoms organize themselves. Itis important that the platform be adjusted so it isslightly out of level. That way, as the motor speeddiminishes the BBs will move to the low side ofthe pan and begin organizing themselves. If thisdoes not happen, apply light finger pressure toone side of the pan to lower it slightly. This willnot affect the vibration movements significantly.While doing the demonstration, also stop thevibration suddenly. This will simulate whathappens when molten material is quenched(cooled rapidly) .

The motor collar required in the materials list isavailable from a hardware store. The purpose ofthe collar is to provide an offcenter weight to theshaft of the motor. The set screw in the collar mayhave to be replaced with a longer one so that itreaches the motor shaft for proper tightening.

Constructing TheVibrating PlatformNote: Specific sizes and part descriptions havenot been provided in the materials list becausethey will depend upon the dimensions of thesurplus electric motor obtained. The motorshould be capable of several hundred revolutionsper minute.

1. Mount three vertical supports on to the woodenbase. They can be attached with corner bracesor by some other means. 2. Mount the surplusmotor to the bottom of the vibrating platform.The specific mounting technique will dependupon the motor. Some motors will featuremounting screws. Otherwise, the motor mayhave to be mounted with some sort of strap.When mounting, the shaft of the motor shouldbe aligned parallel to the bottom of theplafform.

3. Slip the collar over the shaft of the motor andtighten the mounting screw to the shaft. Seethe diagram below for how the shaft and collar

should look when the collar is attached properly.

MotorCollar

Set Screw

Motor Shaft

4. Suspend the platform from the three verticalsupports with elastic shock (bungee) cords orsprings. Add a turnbuckle to one of the cordsfor length adjustment. Shorten that cord anamount equal to the length of the turnbuckleso the platform hangs approximately level.

5. Using hook and loop tape, mount the pan onthe upper side of the vibrating plafform.

6. Place several hundred BBs in the pan. If theBBs spread out evenly over the pan, lengthenthe turnbuckle slightly so the BBs tend toaccumulate along one side of the pan.

7. Turn on the motor by raising the voltage on thevariable transformer. If the device is adjustedproperly, the BBs will start dancing in the panin a representation of melting. Lower thevoltage slowly. The BBs will slow down andbegin to arrange themselves in a tighthexagonal pattern. If you do not observe thiseffect, adjust the leveling of the platformslightly until you do. It may also be helpful toadjust the position of the motor slightly.

Page 142: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

137

Conducting The Experiment1. Turn up the voltage on the variable transformer

until the BBs are dancing about in the pan. Thisrepresents melting of a solid.

2. Shut the variable transformer off. This repre-sents rapid cooling of the liquid to a glassy(amorphous) state. Observe and sketch thepattern of the BBs and of the defects.

3. Turn up the voltage again and gradually reducethe vibration until the BBs are moving slowly.Observe how the BBs move and pack together.

Assessment:Collect the student work sheets.

Extensions:1. Obtain some mineral crystal samples and

examine them for defects. Most crystals willhave some visible defects. The defects will beat a much larger scale than those illustrated inthe student reader. One defect that is easy tofind in the mineral quartz is color variationsdue to the presence of impurities.

2. Investigate the topic of impurities deliberatelyincorporated in crystals used to manufacturecomputer chips. What do these defects do?

3. Design a crystal-growing experiment that couldbe used on the International Space Station.Conduct a ground-based version of that experi-ment. How would the experiment apparatushave to be changed to work on the spacestation?

Page 143: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

138

Crystalline solids are substances whoseatoms or molecules are arranged into a fixedpattern that repeats in three dimensions.Crystalline materials generally begin as a fluid ofatoms or molecules in either the liquid or gaseousstate. As they change to the solid state, the atomsor molecules join together in repeating patterns.Materials that do not form these patterns arecalled amorphous. Glass is a good example of anamorphous material.

The usefulness of a crystal depends on itsstructure. All crystalline materials have varyingdegrees of defects. Defects can take many forms.Gem-quality diamonds sometimes have smallinclusions of carbon (carbon spots) that diminishtheir light refraction and thereby reduce theirvalue. In other crystalline materials, defects mayactually enhance value. Crystals used for solidstate electronics have impurities deliberatelyintroduced into their structure that are used tocontrol their electrical properties. Impurity atomsmay substitute for the normal atoms in a crystal’sstructure or may fit in the spaces within thestructure. Other defects include vacancies, whereatoms are simply missing from the structure, anddislocations, in which a half plane of atoms ismissing. The important thing about crystaldefects is to be able to control their number anddistribution. Uncontrolled defects can result inunreliable electronic properties or weaknesses instructural metals.

Student Reader - 1

Crystallization

Sample Crystal DefectsThe following diagrams show a magnified

view of an ideal two-dimensional crystallinestructure (hexagonal geometry) and a variety ofdefects that the structure might have.

Ideal crystalline structure

Amorphous or glassy structure (when stationary)or a liquid structure (when in motion)

Crystalline structure with surface (grainboundary) defect

Page 144: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

139

Many forces can affect the structure of acrystal. One of the most important forces that caninfluence the structure of a growing crystal isgravity. Growing crystals in microgravity canreduce gravity effects to produce crystals withbetter defined properties. The information gainedby microgravity experiments can lead to improvedcrystal processing on Earth.

The connection between the force ofgravity and the formation of defects varies fromvery simple and straightforward to complicatedand nonintuitive. For example, mercury iodidecrystals can form from the vapor phase. However,at the growth temperature (approximately 125° C)the crystal structure is so weak that defects canform just due to the weight of the crystal. On theother hand, the relationship between residual fluidflows caused by gravity and any resultingcrystalline defects is not well understood and maybe very complex.

Student Reader - 2

Crystalline structure with point defects (vacanciesand substitution impurities)

Crystalline structure (further magnified) withinterstitial defect and edge dislocations

Interstitial

Edge

Page 145: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

140

Name: _________________________________

Based on your observations, describe and sketcheach crystallization stage shown with the model.

Melting:

Student Work Page - 1

Crystallization

Fast Cooling:

Slow Cooling:

Page 146: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

141

Objective:

• To observe buoyancy-drivencovection currents that are created ascrystals grow in a crystal growingsolution.

Science Standards:Science as InquiryPhysical Science- position and motion of objects- properties of objects and materialsUnifying Concepts and ProcessesChange, Constancy, & Measurement

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataInferringPredictingHypothesizing

Mathematics Standards:Measurement

Activity Management:This activity is best done as ademonstration. While it is easy forstudents to grow crystals by followingthe directions, the success of observingthe density-driven convection currentsdepends upon a very still environment.The crystal-growing chamber should beplaced on a firmly mounted counterwhere it will not be disturbed. Theconvection currents are very sensitiveto vibrations. Place a slide projector onone side of the chamber and direct the

Crystal Growth and Buoyancy-Driven Convection Currents

Gravity-driven convection currents are created in acrystal growth chamber by the interaction of thegrowing crystal and the solution.

Aluminum potassium sulfateAIK(SO4)212H20* (alum)Square acrylic box**Distilled waterStirring rodMonofilament fishing lineSilicone cementBeakerSlide projectorProjection screenEye protectionHot plateThermometer Balance*Refer to the chart for the amount

of alum needed for the capacity ofthe growth chamber (bottle) youuse.

**Clear acrylic boxes, about 10x10x13 cm, are available from craftstores. Select a box that has nooptical distortions.

MAT

ER

IALS

AN

D T

OO

LS

Page 147: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

142

light from the projector through the growthchamber so it casts a shadow on the wall behind.If the wall behind the chamber is textured or adark color, tape a piece of white paper there to actas a screen. Viewing may be improved by addingdark paper shields around the screen to reduceoutside light falling on the screen. The projectorcan be replaced by a clear lightbulb of about 100to 150 watts that has a straight filament. Place thebulb in a clip lamp light socket and aim the bulbso the filament is pointing directly at the growthchamber. This will make the bulb serve as a pointsource of light so the shadows will be clear. Donot use a reflective lamp shade with the light.

When preparing the crystal growing solution, besure to follow routine safety precautions such aswearing eye protection. You can obtain thischemical from school science supply companiesor even in food stores in the spice section. Alumis used in pickling.

To produce large alum crystals, it is necessary toobtain seed crystals first. This is accomplished bydissolving some alum in a small amount of waterand setting it aside for a few days. Plan to do thisstep several weeks before you will use thedemonstration with your students. To save time,dissolve as much alum as you can in warm water.This will produce a supersaturated solution whenthe liquid cools and crystallization will startshortly. After the seed crystals form (about 3-5mm in size) pour the solution through some filterpaper or a paper towel to capture the seeds. Letthem dry before attaching the fishing line. Inattaching the line, simply place a dab of silicone

cement on a piece of paper and then touch theend of a short length of monofilament fishing lineto the cement. Then, touch the same end of theline to the crystal. Prepare several seed crystals inthis manner. When the cement dries, you will beready for the steps below.

You may discover mysterious variations in thegrowth of the crystal over several days.Remember, the amount of alum that can bedissolved in a given quantity of water will varywith the water’s temperature. Warm water canhold more alum than cold water. If the air-conditioning in a building is shut off for theweekend, the temperature of the alum solutionwill climb with the room’s temperature and someor all of the crystal may dissolve back into thewater.

Procedure:1. Prepare the crystal growth solution by dissolv-

ing powdered or crystalline alum in a beaker ofwarm water. The amount of alum that can bedissolved in the water depends upon theamount of water used and its temperature.Refer to the plot (Alum Solubility in Water) forthe quantity required.

2. When no more alum can be dissolved in thewater, transfer the solution to the growthchamber acrylic box.

3. Punch or drill a small hole through the centerof the lid of the box. Thread the seed crystalline through the hole and secure it in place witha small amount of tape. Place the seed crystalin the box and place the lid on the box at a 45degree angle. This will expose the surface ofthe solution to the outside air to promoteevaporation. It may be necessary to adjust thelength of the line so the seed crystal is severalcentimeters above the bottom of the box.

4. Set the box aside in a place where it can beobserved for several days without being dis-turbed. If the crystal shouid disappear, dissolvemore alum into the solution and suspend a newseed crystal. Eventually, growth will begin.

Page 148: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

143

5. Record the growth rate of the crystal by mea-suring it with a metric ruler. The crystal mayalso be removed and its mass measured on abalance.

6. Periodically observe the fluid flow associatedwith the crystal’s growth by directing the lightbeam of a slide projector through the box to aprojection screen. Observe plumes around theshadow of the crystal. Convection currents inthe growth solution distort the light passingthrough the growth solution. Refer to thediagram at the beginning of this activity forinformation on how the observation is set up.

Assessment:Collect the student work sheets.

Extensions:1. Try growing other crystals. Recipes for crystals

can be found in reference books on crystalgrowing.

2. Collect natural crystals and observe theirsurfaces and interiors (if transparent). Look foruniformity of the crystals and for defects. Makea list of different kinds of defects (fractures,bubbles, inclusions, color variations, etc.).Discuss what conditions must have existed innature at the time of the crystal’s formation orafter its formation to cause the defects.

3. Review scientific literature for results frommicrogravity crystal-growing experiments.

Page 149: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

144

Student Reader - 1

Crystals can be grown using a variety of methods.One of the simplest methods involves dissolving asolid into a liquid. As the liquid evaporates, thesolid comes out of solution and forms a crystal(or many crystals). This can be done with sugaror salt or a variety of other compounds such asalum (aluminum potassium sulfate), LAP (L-arginine phosphate), or TGS (triglycine sulfate).

The usual procedure for growing crystals from asolution is to create the solution first. In thisactivity, a quantity of alum is dissolved into warmwater. Warm water was used to increase theamount of alum that could be dissolved. You mayhave observed this effect by stirring sugar into acup of hot coffee or tea. Hot liquids can dissolvemore sugar than cold liquids. After the alum wasdissolved, the solution was allowed to cool backdown to room temperature. As a result, the waterheld more alum than it normally could at thattemperature. The solution was supersaturated. Aseed crystal was suspended in the solution and itbegan to grow. The excess alum dissolved in thewater migrated to the crystal and was depositedon its surface. Because the crystal growthchamber was open to the surrounding air, thesolution began evaporating. This continued thecrystal growth process because the alum left overfrom the evaporated water was deposited on thecrystal.

At first glance, the growth process of the alumcrystal looks very quiet and still. However,examination of the solution and growing crystalwith light to produce shadows shows thatcurrents exist in the solution. These currentsbecome visible when light is projected throughthem because the convection currents distort thelight rays, making them appear as dark plumes on

Crystal Growth and Buoyancy-DrivenConvection Currents

the screen. This image on the screen is called ashadowgraph.

Where do these convection currents come from?The answer has to do with the difference in theamount of alum in solution near the growingcrystal compared with the solution near the wallof the growth chamber. Except for near the

Water molecules in this diagram are represented by blackdots and the alum dissolved represented by the lighter dots.Throughout most of the solution, the dots are randomlymixed but, next to the crystal, the dots are mostly black.This happens because the alum nearest the growing crystalattaches to the crystal structure, leaving behind the water.The remaining water is buoyant and rises while denserwater with more dissolved alum moves next to the crystalto take its place.

Page 150: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

145

Student Reader - 2

crystal, the solution is homogeneous. This meansit has the same composition and density. Thesolution near the crystal is another matter. Aseach molecule of alum leaves the solution tobecome deposited on the crystal’s surface, thesolution left behind becomes slightly less densethan it was. The less dense solution is buoyantand begins to rise in the chamber. More densesolution moves closer to the crystal to take itsplace. The alum in the replacement solution alsodeposits on the crystal, causing this solution tobecome less dense as well. This keeps theconvection current moving.

Microgravity scientists are interested in theconvection currents that form around a crystalgrowing in solution. The currents may beresponsible for the formation of defects such asliquid inclusions. These are small pockets ofliquid that are trapped inside the crystal. Thesedefects can degrade the performance of devicesmade from these materials. The virtual absence ofbuoyancy-driven convection in a microgravityenvironment may result in far fewer inclusionsthan in crystals grown on Earth. For this reason,solution crystal growth has been an active area ofmicrogravity research.

Shadowgraph image of a growth plumerising from a growing crystal.

Page 151: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

146

Crystal Growth and Buoyancy-DrivenConvection Currents

Name: _________________________________

1. In the box to the right, make a sketch of what you observed in the shadowgraph of a crystal growingfrom solution.

2. Explain below what is happening.

Student Work Sheet- 1

Shadowgraph for growing alum crystal

3. In the box to the right, sketch what a shadowgraph should look like for a crystal that is dissolvingback into solution.

4. Explain your diagram below.

Shadowgraph for dissolving alum crystal

Page 152: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

147

Student Work Sheet- 1

5. Draw a picture in the space to the right of whatyou think the shadowgraph should look like fora crystal grown from solution in a microgravityenvironment.

6. Explain your picture below.Shadowgraph for alum crystal grown inmicrogravity

Page 153: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

148

Rapid CrystallizationObjective:

• To investigate the growth ofcrystals under different tempera-ture conditions.

Science Standards:Science as InquiryPhysical Science- properties of objects and materialsUnifying Concepts and ProcessesChange, Constancy, & Measurement

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataInferringPredictingInterpreting DataControlling VariablesInvestigating

Mathematics Standards:CommunicationMeasurement

Activity Management:This activity is best done withcooperative learning groups of twoor three students. This will minimizethe number of heat packs that haveto be obtained. Heat packs are soldat camping supply stores. It isimportant to get the right kind ofpack. The pack, sold under differentnames, consists of a plastic pouch(approximately 9 by 12 centimetersin size) containing a solution ofsodium acetate and water and asmall metal disk. When the disk

The rapid growth of crystals in a heat pack isobserved under different heating conditions.

Heat pack hand warmers(1 or more per group)

Water boiler (an electric kitchenhot pot can be used)

Styrofoam food tray(1 per group)

Metric thermometer(1 or more per group)

Observation and data table(1 per student group)

CoolerClock or other timer

MAT

ER

IALS

AN

D T

OO

LS

clicked or snapped, crystals begin to form andheat is released. The pack can be reused byreheating until all the crystals are dissolved.

Assemble all the materials needed for the activityin sets for the number of student groups youhave. Prepare the heat packs by heating any thatare solidified until all the crystals dissolve.

Page 154: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

149

Allow one half of the packs to cool to roomtemperature. Maintain the other packs at atemperature of about 45°C. This can be done byplacing the packs in an insulated cooler withsome hot water until the packs are needed.

Before starting the experiment, discuss the datacollection procedure. To reduce heat conductivityproblems, heat packs are placed on theStyrofoam food tray with the bulb of athermometer slipped between the pack and thetray. Discuss with the students why the tray isnecessary and ask them where the bestplacement of the bulb should be. Remindstudents that the thermometer should be placedthe same way for each test. Give each studentgroup one student data sheet for each test to beperformed.

Begin with observation of the room temperaturepack first. The students should be prepared tomake observations immediately after the disk isclicked. Complete crystallization should take lessthan a minute. Since the crystallization process isdramatic, demonstrate the clicking process withanother heat pack and pass it around for studentsto feel. If you have some sort of video displaysystem, show crystallization on the television as itis happening. This may help students focus onthe investigation when they start their own packscrystallizing. Distribute the second pack afterobservations of the first pack are complete.Crystallization of the second pack will take severalminutes to complete.

Students will discover that heat packs with higherinitial temperatures will take longer to crystallize.Crystals will be more defined than those formingin packs with cooler initial starting temperatures.Depending upon the initial temperature, crystalsmay resemble needles or blades. Gravity willinfluence their development. Crystals will settle tothe bottom of the pack and intermingle, causingdistortions. Crystals forming in an initially coolheat packs will be needlelike but, because so

many form at once, the growth pattern will befan-shaped.

Use the questions below as a guide to discuss theresults of the investigation.

1. Is there any relationship between the initialtemperature of the pouch and the temperatureof the pouch during crystallization?

2. Is there a relationship between the initialtemperature of the pouch and the time it takesfor the pouch to completely solidify?

3. Do other materials, such as water, release heatwhen they freeze?

Assessment:Collect the student work sheets.

Extensions:1. Discuss what might happen if the heat pack

were crystallized in microgravity. What effectdoes gravity have? Hold the pack vertically withthe steel disk at the bottom and trigger thesolidification. Repeat with the disk at the top.

2. Try chilling a heat pack pouch in a freezer andthen triggering the solidification.

Page 155: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

150

Student Reader - 1

and CrystalsCrystals are solids composed of atoms, ions, ormolecules arranged in orderly patterns that repeatin three dimensions. The geometric form of acrystal visible to the naked eye can provide cluesto the arrangement inside. Many of the uniqueproperties of materials, such as strength andductility, are a consequence of crystallinestructure.

It is easy to get confused about the natureof crystals because the word crystal is frequentlymisused. For example, a crystal chandelier is notcrystal at all. Crystal chandeliers are made ofglass which is a solid material but does not havea regular interior arrangement. Glass is called anamorphous material because it does not have aregular interior arrangement of atoms.

Scientists are very interested in growingcrystals in microgravity because gravity ofteninterferes with the crystalgrowing process,leading to defects forming in the crystal structure.The goal of growing crystals in microgravity isnot to develop crystal factories in space but tobetter understand the crystal-growing processand the effects that gravity can have on it.

In this activity, you will be investigatingcrystal growth with a hand warmer. The handwarmer consists of a plastic pouch filled with afood-grade solution of sodium acetate and Swater. Also in the pouch is a small disk ofstainless steel.

Heat Pack

Snapping the disk triggers the crystallizationprocess. (The exact cause for this phenomena isnot well understood.) The pouch is designed sothat at room temperature the water contains manymore molecules of sodium acetate than wouldnormally dissolve at that temperature. This iscalled a supersaturated solution. The solutionremains that way until it comes in contact with aseed crystal or some way of rapidly introducingenergy into the solution which acts as a triggerfor the start of crystallization. Snapping the metaldisk inside the pouch delivers a sharp mechanicalenergy input to the solution that triggers thecrystallization process. Crystallization takes placeso rapidly that the growth of crystals can easily

be observed. Heat is released during theprecipitation that maintains the pouchtemperature at about 54°C for about 30minutes. This makes the pouch ideal for ahand warmer. Furthermore, the pouch canbe reused by reheating and dissolving thesolid contents again.

Page 156: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

151

Student Work Sheet - 1

Heat PackExperimentData Sheet

Test number: ____________

Initial temperature of pouch: _______________

Temperature and time atbeginning of crystallization: ________________

Temperature and time atend of crystallization: _____________________

Length of time forcomplete crystallization: ___________________

Describe the crystals(shape, growth rate, size, etc.)

Test number: ____________

Initial temperature of pouch: ______________

Temperature and timeat beginning of crystallization: _____________

Temperature and time atend of crystallization:m __________________

Length of time forcomplete crystallization: _________________

Describe the crystals(shape, growth rate, size, etc.)

Team Member Names:

Sketch of Crystals

Sketch of Crystals

Page 157: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

152

Microscopic Observation ofCrystal GrowthObjective:

• To observe crystal nucleation andgrowth rate during directionalsolidification .

Science Standards:Science as InquiryPhysical Science- position and motion of objects- properties of objects and materialsUnifying Concepts and ProcessesChange, Constancy, & Measurement

Science Process Skills:ObservingCommunicatingInvestigating

Activity ManagementThe mannite part of this activityshould be done as a demonstration,using a microprojector ormicroscope with a television system.It is necessary to heat a smallquantity of crystalline mannite on aglass slide to 168°C and observe itsrecrystallization under magnification.The instructions call for melting themannite twice and causing it to coolat different rates. It is better toprepare separate samples so theycan be compared to each other. Th~slide that is cooled slowly can easilybe observed under magnification ascrystallizes. You may not have timeto observe the rapidly chilled sampleproperly before crystallization iscomplete. The end result, however,

A microprojector is used to observe crystalgrowth.

Bismarck brown YMannite (d-mannitol)HOCH2(CHOH)4CH20HSalol (Phenyl salicylate)

C13H10O3MicroprojectorStudent microscopes (instead of

a microprojector)Glass microscope slides with

cover glassCeramic bread-and-butter plateRefrigeratorHot plate or desktop coffee cup

warmerForcepsDissecting needleSpatulaEye protection

MAT

ER

IALS

AN

D T

OO

LS

will be quite apparent under magnification. Ifstudents will be conducting the second part oftheactivity, it is suggested that you prepareseveral sets of mannite slides so they may be

Page 158: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

153

distributed for individual observations. The salolobservations are suitable for a demonstration, butbecause of the lower melting temperature (48°C),it is much safer for students to work with that themannite. A desktop coffee cup warmer issufficient for melting the salol on a glass slide.Because of the recess of the warmer’s plate, it isbest to set several large metal washers on theplate to raise its surface. The washers willconduct the heat to the slide and make it easier topick up the heated slide with forceps. Point out tothe students that they should be careful whenheating the salol because overheating will causeexcessive evaporation and chemical odors, andwill increase the time it takes for the material tocool enough for crystallization to occur. The slideshould be removed from the hot plate just as itstarts melting. The glass slide will retain enoughheat to complete the melting process.

Only a very small amount of bismarck brown isneeded for the last part of the activity with salol.Only a few dozen grains are needed. Usually justtouching the spatula to the chemical causesenough particles to cling to it. Gently tap thespatula held over the melted salol to transfer theparticles. It will be easier to do this if the salolslide is placed over a sheet of white paper. Thiswill make it easier to see that the particles havelanded in the salol.

If students are permitted to do individual studies,go over the procedures while demonstratingcrystallization with the d-mannitol. Have studentspractice sketching the crystallized mannitolsamples before they try sketching the salol.

Refer to the chemical notes below for safetyprecautions required for this activity.

Notes On Chemicals Used:Bismarok Brown Y

Bismarck brown is a stain used to dye bonespecimens for microscope slides. Becausebismarck brown is a stain, avoid getting it onyour fingers. Bismarck brown is water soluble.

Mannite (d-mannitol)HOCH2(CHOH)4CH20H Mannite has a meltingpoint of approximately 168°C. It may be harm-ful if inhaled or swallowed. Wear eye protectionand gloves when handling this chemical.Conduct the experiment in a well-ventilatedarea.

Salol (phenyl salicylate)C13H10O3It has a melting point of 43° C. It may irritateeyes. Wear eye protection.

Procedure: Observations ofMannite1. Place a small amount of mannite on a micro-

scope slide and place the slide on a hot plate.Raise the temperature of the hot plate until themannite melts. Be careful not to touch the hotplate or heated slide. Handle the slide withforceps.

2. After melting, cover the mannite with a coverglass and place the slide on a ceramic bread-and-butter plate that has been chilled in arefrigerator. Permit the liquid mannite tocrystallize.

3. Observe the sample with a microprojector. Notethe size, shape, number, and boundaries of thecrystals.

4. Prepare a second slide, but place it immedi-ately on the microprojector stage. Permit themannite to cool slowly. Again observe the size,shape, and boundaries of the crystals. Markand save the two slides for comparison usingstudent microscopes. Forty power is sufficientfor comparison. Have the students makesketches of the crystals on the two slides andlabel them by cooling rate.

Page 159: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

154

Observations of Salol5. Repeat the procedure for mannite (steps 1–4)

with the salol, but do not use glass cover slips.Use a desktop coffee cup warmer to melt thesalol. It may be necessary to add a seed crystalto the liquid on each slide to start the crystalli-zation. Use a spatula to carry the seed to thesalol. If the seed melts, wait a moment and tryagain when the liquid is a bit cooler. (If themicroprojector you use does not have heatfilters, the heat from the lamp may remelt thesalol before crystallization is completed.)

6. Prepare a new salol slide and place it on themicroprojector stage. Drop a tiny seed crystalinto the melt and observe the solid-liquidinterface.

7. Remelt the salol on the slide and sprinkle a tinyamount of bismarck brown on the melt. Drop aseed crystal into the melt and observe themotion of the bismarck brown granules. Thegranules will make the movements of the liquidvisible. Pay close attention to the granules nearthe growing edges and points of the salolcrystals.

Assessment:Collect the student data sheets.

Extensions:1. Design a crystal-growing experiment that could

be flown in space. The experiment should beself-contained and the only astronaut involve-ment that of turning a switch on and off.

2. Design a crystal-growing experiment forspaceflight that requires astronaut observa-tions and interpretations.

3. Research previous crystal-growing experi-ments in space and some of the potentialbenefits researchers expect from space-growncrystals.

Page 160: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

155

Student Reader - 1

Crystal Growth

Directional solidification refers to a process bywhich a liquid is transformed (by freezing) into asolid through the application of a temperaturegradient (a temperature difference over aspecified distance such as 1 0oC/cm) in whichheat is removed in one direction. The heat travelsdown the temperature gradient from hot to cold.A container of liquid will turn to a solid in thedirection the temperature is lowered. If this liquidhas a solute (something dissolved in the liquid)present, typically some of the solute will berejected into the liquid ahead of the liquid/solidinterface. However, not all of the solute can becontained in the solid as it forms; the remainingsolute is pushed back into the liquid near theinterface. This phenomenon has many importantconsequences for the solid including how muchof the solute eventually ends up in the solid. Theconcentration of solute in the solid can controlthe electrical properties of semiconductors andthe mechanical and corrosion properties of

metals. As a result, solute rejection is studiedextensively in solidification experiments.

The rejected material tends to build up atthe interface (in the liquid) to form a layer rich insolute. This experiment demonstrates whathappens when the growth rate is too fast andsolute in the enriched layer is trapped.

Fluid flow in the melt can also affect thebuildup of this enriched layer. On Earth, fluids thatexpand become less dense. This causes a verticalflow of liquid which will interfere with theenriched layer next to the growing solid. In space,by avoiding this fluid flow, a more uniformenriched layer will be achieved. This, in turn, canimprove the uniformity with which the solute isincorporated into the growing crystal.

Sample Microscope SketchesMannite Crystallization

Slow Cooling Fast Cooling

Page 161: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

156

Name: ________________________________

1. Study the mannite crystallization slides. Sketch what you observe in the two circles below. Identifythe cooling rate for each slide and the magnification you used for your observatlons.

Mannite (d-Mannitol)

Cooling Rate: _______________________

Magnification: ______________________

Microscopic Observation of Crystals

Student Work Sheet - 1

Cooling Rate: _________________________

Magnification: ________________________

Describe below the difference between the two mannite samples.

How can you explain these differences?

Page 162: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

157

Student Work Sheet - 2

2. Prepare the salol samples according to instructions provided by your teacher. Remember to weareye protection as you handle the chemical. Study the salol crystallization slides. Sketch what youobserve in the two circles below. Identify the cooling rate for each slide and the magnification youused for your observations.

Cooling Rate: _____________________

Magnification: _____________________

Cooling Rate: _____________________

Magnification: _____________________

Salol (Phenyl Salicylate)

Describe below the difference between the two salol samples.

How can you explain these differences?

Page 163: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

158

3. Prepare a third salol sample according to instructions provided by your teacher. Remember to weareye protection as you handle the chemical. Adjust the sample on the microscope stage so you canobserve the interface between the growing crystals and the melted chemicals. In particular, look atwhat happens to the bismarck brown particles as the growing crystals contact them. Sketch whatyou observe in the circle below.

Student Work Sheet - 3

Cooling Rate: ________________________

Magnification: _______________________

What happens to the resulting crystals when impurities (bismarck brown) exist in the melt?

Slow

What caused the circulation patterns of the liquid around the growing crystal faces? Do you thinkthese circulation patterns affect the atomic arrangements of the crystals? How?

How do you think the growth of the crystals would be affected by growing them in microgravity?

Page 164: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

159

Zeolite Crystal GrowthObjective:

• To grow zeolite crystals andinvestigate how gravity affectstheir growth.

Science Standards:Science as InquiryPhysical ScienceUnifying Concepts and ProcessesChange, Constancy, & MeasurementScience in Personal and Social

Perspectives

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataControlling VariablesInvestigating

Mathematics Standards:Measurement

Activity Management:The preparation of zeolite crystals,although not difficult, is an involvedprocess. A number of differentchemicals must be carefully weighedand mixed. You may wish to preparethe chemicals yourself or assignsome of your more advancedstudents to the task. Refer to thematerials and tools list on the nextpage for a detailed list of what isrequired.

This activity involves maintaining ahot water bath continuously for up to8 days. If you do not have thefacilities to do this, you can conduct

Zeolite crystals are being grown in a hot waterbath.

the experiment for just the 0 and 1 TEA(triethanolamine) samples described below.Crystals may also be formed if the hot water bathis turned off at the end of the school day andturned on the succeeding day. Crystallizationtimes will vary under this circumstance, and closemonitoring of the formation of the crystallineprecipitate will be necessary.

Following the growth of zeolite crystals, smallsamples can be distributed to student groups formicroscopic study.

Procedure:1. While wearing hand and eye protection, weigh

0.15 grams of sodium hydroxide and place it ina 60 ml, high-density polyethylene bottle. Add60 ml of distilled water to the bottle and cap it.Shake the bottle vigorously until the solids arecompletely dissolved. Prepare a second bottleidentical to the first.

2. Add 3.50 grams of sodium

Page 165: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

160

metasilicate to one of the bottles and again cap itand shake it until all the solids are dissolved.Mark this bottle “silica solution.” To the secondbottle, add 5.6 grams of sodium aluminate andcap it and shake it until all the solids aredissolved. Mark this bottle “alumina solution.”3. Using a permanent marker pen, mark the four,30 ml high-density polyethylene bottles with thefollowing identifications: 0 TEA, 1 TEA, 5 TEA, and10 TEA.

Sodium aluminate NaAIO2FW=81.97Sodium metasilicate anhydrous,

purum, Na2O3Si, FW=122.06Sodium hydroxide pellets,97+%, average compositionNaOH, FW=40Triethanolamine (TEA), 98%(HOHCH2)3N, FW=149.19Distilled water1000 ml Pyrex® glass beakerAluminum foilMetric thermometer with range up

to 100°CLaboratory hot plate2-60 ml high-density polyethylene

bottles with caps4-30 ml high-density polyethyene

bottles with capsPlastic glovesGogglesGlass microscope slidesPermanent marker pen for

marking on bottlesWaterproof tapeLead fishing sinkersTongsEyedropperOptical microscope, 400X

MAT

ER

IALS

AN

D T

OO

LS4. Place 0.85 grams of TEA into the bottle marked

“1 TEA.” Place 4.27 grams of TEA into thebottle marked “5 TEA.” Place 8.55 grams ofTEA into the bottle marked “10 TEA.” Do notplace any TEA into the bottle marked “0 TEA.”

5. Add 10 ml of the alumina solution to each ofthe bottles. Also add 10 ml of the silica solutionto each bottle.

6. Cap each bottle tightly and shake vigorously.Secure each cap with waterproof tape and tapea lead sinker to the bottom of each bottle. Thesinker should weigh down the bottle so it willbe fully immersed in the hot water.

7. Prepare a hot water bath by placing approxi-mately 800 ml of water in a 1000 ml Pyrexsbeaker. Place the four weighted bottles into thebeaker. The bottles should be covered by thewater. Cover the beaker with aluminum foil andpunch a small hole in the foil to permit a metricthermometer to be inserted. Fix the thermom-eter in such a way as to prevent it from touch-ing the bottom of the beaker. Place the beakeron a hot plate and heat it to between 8$ and95° C. It will be necessary to maintain thistemperature throughout the experiment.Although the aluminum foil will reduce evapo-ration, it will be necessary to periodically addhot (85 to 90° C) water to the beaker to keepthe bottles covered.

8. After 1 day of heating, remove the bottlemarked 0 TEA from the bath with a pair oftongs. Using an eyedropper, take a smallsample of the white precipitate found on thebottom of the bottle. Place the sample on aglass microscope slide and examine for thepresence of crystals under various magnifica-tions. Make sketches or photograph anycrystals found. Be sure to identify magnifica-tion of the sketches or photographs and esti-mate the actual sizes of the crystals. Determinethe geometric form of the crystals. Look forcrystals that have grown together.

Page 166: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

161

9. Repeat procedure 8 for the 1 TEA bottle after 2days of heating. Repeat the procedure again forthe 5 TEA bottle after 5 days and for the 10 TEAbottles after 8 days. Compare the size, shape,and intergrowth of the crystals formed in eachof the bottles.

AssessmentCollect student sketches and written descriptionsof the zeolite crystals.

Extension:1. Obtain zeolite filter granules from a pet shop.

The granules are used for filtering ammoniafrom aquarium water. Set up a funnel with filterpaper and fill it with the granules. Slowly poura solution of water and household ammonia(ammonia without lemon or other maskingscents) into the granules. Collect the liquidbelow and compare the odor of the filteredsolution and the unfiltered solution. Try runningthe filtered solution through a second time andagain compare the odors. Be sure to wear eyeprotection.

Page 167: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

162

Zeolites are crystals made up of the elementssilicon, aluminum, and oxygen. The crystalsconsist of alternatingarrays of silica (beachsand, SiO2) and alumina(aluminum oxide, Al203)and can take on manygeometric forms such ascubes and tetrahedra.Internally, zeolites are rigidsponge-like structures withuniform but very smallopenings (e.g., 0.1 to 1.2nanometers or 0.1 to 1.2 X10-9 meters). Because ofthis property, theseinorganic crystals aresometimes called“molecular sieves.” Forthis reason, zeolites areemployed in a variety ofchemical processes. Theyallow only molecules ofcertain sizes to enter theirpores while keepingmolecules of larger sizes out. In a sense, zeolitecrystals act like a spaghetti strainer that permitshot water to pass through while holding back thespaghetti. As a result ot tnis filtering action,zeolites enable chemists to manipulate moleculesand process them individually.

The many chemical applications for zeolitecrystals make them some of the most usefulinorganic materials in the world. They are used ascatalysts in a large number of chemical reactions.(A catalyst is a material that has a pronounced

Student Reader- 1

Zeoliteseffect on the speed of a chemical reaction withoutbeing affected or consumed by the reaction.)

Scientists use zeolitecrystals to produce allthe world’s gasolinethough a chemicalprocess called catalyticcracking. Zeolite crystalsare often used infiltration systems forlarge municipalaquariums to removeammonia from thewater. Because they areenvironmentally safe,zeolites have been usedin laundry detergents toremove magnesium andcalcium ions. Thisgreatly improvesdetergent sudsing inmineral-rich “hard”water. Zeolites can alsofunction as filters forremoving low

concentrations of heavy metal ions, such as Hg,Cd, and Pb, or radioactive materials from wastewaters.

Although scientists have found many beneficialuses for zeolites, they have only an incompleteunderstanding of how these crystals nucleate(first form from solution) and grow (becomelarger). When zeolites nucleate from a watersolution, their density (twice that of water) causesthem to sink to the bottom of the specialcontainer (called an autoclave) they are growing

Page 168: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

163

Student Reader- 2

in. This is a process called sedimentation, and itcauses the crystals to fall on top of each other. Asthese crystals continue to grow after they havesettled, some merge to produce a large number ofsmall, intergrown zeolite crystals instead oflarger, separate crystals.

Zeolite crystal growth research in themicrogravity environment of Earth orbit isexpected to yield important information forscientists that may enable them to produce betterzeolite crystals on Earth. In microgravity,sedimentation is significantly reduced and so isgravity-driven convection.

Zeolite crystals grown in microgravity are often ofbetter quality and larger in size than similarcrystals grown in control experiments on Earth.Exactly how and why this happens is not fullyunderstood by scientists. Zeolite crystal growthexperiments on the Space Shuttle and on thefuture International Space Station should provideinvaluable data on the nucleation and growthprocess of zeolites. Such an understanding maylead to new and more efficient uses of zeolitecrystals.

Page 169: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

164

Name: _______________________

Instructions:Observe through a microscope each zeolite crystal sample provided to you by your teacher. Sketch thesamples in the circles provided and write a brief description of what you see.

Sample 1

__________________ TEA

Sample age ________________ day(s)

Description:

Sample 2

__________________ TEA

Sample age ________________ day(s)

Description:

Microscopic Observation ofZeolite Crystals

Student Work Sheet - 1

Magnification: ____________ X

Magnification: ____________ X

Page 170: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

165

Student Work Sheet - 2

Sample 3

__________________ TEA

Sample age ________________ day(s)

Description

Sample 4

__________________ TEA

Sample age ________________ day(s)

Description

QUESTIONS:

1. What geometric form (crystal habit) did the zeolite crystals assume as they grew? Was there morethan one form present? How did the zeolite crystals appear when they grew into each other?

2. Can you detect any relationship between the length of time crystals were permitted to form, theirsize and their geometric perfection?

3. Would additional growing time yield larger crystals? Why or why not?

Magnification: ____________ X

Magnification: ____________ X

Page 171: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

167

NASA Resources for Educators

Regional Educator Resource Centers (RERCs) offermore educators access to NASA educational materials. NASAhas formed partnerships with universities, museums, and othereducational institutions to serve as RERCs in many states. Acomplete list of RERCs is available through CORE, or electroni-cally via NASA Spacelink at http://spacelink.nasa.gov

NASA On-line Resources for Educators provide currenteducational information and instructional resource materials toteachers, faculty, and students. A wide range of information isavailable, including science, mathematics, engineering, andtechnology education lesson plans, historical information re-lated to the aeronautics and space program, current statusreports on NASA projects, news releases, information on NASAeducational programs, useful software and graphics files. Edu-cators and students can also use NASA resources as learningtools to explore the Internet, accessing information about educa-tional grants, interacting with other schools which are alreadyon-line, and participating in on-line interactive projects, commu-nicating with NASA scientists, engineers, and other team mem-bers to experience the excitement of real NASA projects.

Access these resources through the NASA Education HomePage: http://www.hq.nasa.gov/education

NASA Television (NTV) is the Agency's distribution system forlive and taped programs. It offers the public a front-row seat forlaunches and missions, as well as informational and educationalprogramming, historical documentaries, and updates on the latestdevelopments in aeronautics and space science. NTV is transmittedon the GE-2 satellite, Transponder 9C at 85 degrees Westlongitude, vertical polarization, with a frequency of 3880 megahertz,and audio of 6.8 megahertz.

Apart from live mission coverage, regular NASA Televisionprogramming includes a Video File from noon to 1:00 pm, a NASAGallery File from 1:00 to 2:00 pm, and an Education File from 2:00to 3:00 pm (all times Eastern). This sequence is repeated at3:00 pm, 6:00 pm, and 9:00 pm, Monday through Friday. The NTVEducation File features programming for teachers and students onscience, mathematics, and technology. NASA Televisionprogramming may be videotaped for later use.

For more information on NASA Television, contact:NASA Headquarters, Code P-2, NASA TV, Washington, DC20546-0001 Phone: (202) 358-3572NTV Home Page: http://www.hq.nasa.gov/ntv.html

How to Access NASA's Education Materials and Services,EP-1996-11-345-HQ This brochure serves as a guide to access-ing a variety of NASA materials and services for educators.Copies are available through the ERC network, or electronicallyvia NASA Spacelink. NASA Spacelink can be accessed at thefollowing address: http://spacelink.nasa.gov

AK, AZ, CA, HI, ID, MT, NV, OR,UT, WA, WYNASA Educator Resource CenterMail Stop 253-2NASA Ames Research CenterMoffett Field, CA 94035-1000Phone: (415) 604-3574

CT, DE, DC, ME, MD, MA, NH,NJ, NY, PA, RI, VTNASA Educator Resource LaboratoryMail Code 130.3NASA Goddard Space Flight CenterGreenbelt, MD 20771-0001Phone: (301) 286-8570

CO, KS, NE, NM, ND, OK, SD, TXJSC Educator Resource CenterSpace Center HoustonNASA Johnson Space Center1601 NASA Road OneHouston, TX 77058Phone: (281) 483-8696

FL, GA, PR, VINASA Educator Resource LaboratoryMail Code ERLNASA Kennedy Space CenterKennedy Space Center, FL 32899-0001Phone: (407) 867-4090

KY, NC, SC, VA, WVVirginia Air and Space MuseumNASA Educator Resource Center forNASA Langley Research Center600 Settler's Landing RoadHampton, VA 23669-4033Phone: (757) 727-0900 x 757

IL, IN, MI, MN, OH, WINASA Educator Resource CenterMail Stop 8-1NASA Lewis Research Center21000 Brookpark RoadCleveland, OH 44135-3191Phone: (216) 433-2017

AL, AR, IA, LA, MO,TNU.S. Space and Rocket CenterNASA Educator Resource Center forNASA Marshall Space Flight Cente rP.O. Box 070015Huntsville, AL 35807-7015Phone: (205) 544-5812

MSNASA Educator Resource CenterBuilding 1200NASA John C. Stennis Space CenterStennis Space Center, MS 39529-6000Phone: (601) 688-3338

NASA Educator Resource CenterJPL Educational OutreachMail Stop CS-530NASA Jet Propulsion Laboratory4800 Oak Grove DrivePasadena, CA 91109-8099Phone: (818) 354-6916

CA cities near the centerNASA Educator Resource Center forNASA Dryden Flight Research Center45108 N. 3rd Street EastLancaster, CA 93535Phone: (805) 948-7347

VA and MD's Eastern ShoresNASA Educator Resource LabEducation Complex - Visitor CenterBuilding J-1NASA Wallops Flight FacilityWallops Island, VA 23337-5099Phone: (757) 824-2297/2298

NASA’s Central Operation of Resources for Educa-tors (CORE) was established for the national and interna-tional distribution of NASA-produced educational materials inaudiovisual format. Educators can obtain a catalogue and anorder form by one of the following methods:

• NASA CORELorain County Joint Vocational School15181 Route 58 SouthOberlin, OH 44074

• Phone (440) 774-1051, Ext. 249 or 293• Fax (440) 774-2144• E-mail [email protected]• Home Page: http://spacelink.nasa.gov/CORE

Educator Resource Center NetworkTo make additional information available to the educationcommunity, the NASA Education Division has created theNASA Educator Resource Center (ERC) network. ERCs con-tain a wealth of information for educators: publications, refer-ence books, slide sets, audio cassettes, videotapes, telelectureprograms, computer programs, lesson plans, and teacherguides with activities. Educators may preview, copy, or receiveNASA materials at these sites. Because each NASA FieldCenter has its own areas of expertise, no two ERCs are exactlyalike. Phone calls are welcome if you are unable to visit the ERCthat serves your geographic area. A list of the centers and theregions they serve includes:

Page 172: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades

Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology,EG-1997-08-110-HQ, Education Standards Grades 5–8 (∆), 9–12 (❏)

168

Educational VideotapeEducational Videotapes and slide sets are availablethrough the Educator Resource Center Network andCORE (see listing on page 167).

Microgravity- Length 23:24

This video describes the restrictions that gravityimposes on scientific experimentation and how theycan be greatly reduced in the exciting researchenvironment of the Space Shuttle and the Interna-tional Space Station.

NASA publishes a variety of educational resourcessuitable for classroom use. The following resourcesspecifically relate to microgravity and living, working,and science research in the microgravity environ-ment. Resources are available from different sourcesas noted.

SlidesMicrogravity Science - Grades: 8-12This set of 24 slides illustrates the basic concepts ofmicrogravity and describes four areas of microgravityresearch, including: biotechnology, combustionscience, fluid physics, and materials science. 1994

NASA PublicationsNASA (1980), Materials Processing In Space: EarlyExperiments, Scientific and Technical InformationBranch, NASA Headquarters, Washington, DC.

NASA (1982), Spacelab, EP-165, NASAHeadquarters, Washington, DC.

NASA (1976-Present), Spinoff. NASA Headquarters,Washington, DC (annual publication).

NASA (1994), “Microgravity News,” MicrogravityScience Outreach, Mail Stop 359, NASA LangleyResearch Center, Hampton, VA (quarterly newslet-ter)

NASA (1988), Science in Orbit - The Shuttle andSpacelab Experience: 1981 -1986, NASA MarshallSpace Flight Center, Huntsville, AL.

NASA Educational MaterialsSuggested Reading

BooksFaraday, M., (1988) The Chemical History of aCandle, Chicago Review Press, Chicago, IL.

Halliday, D. & Resnick, R., (1988) Fundamentals ofPhysics, John Wiley & Sons, Inc., New York, NY.

Holden, A. & Morrison, P., (1982), Crystals andCrystal Growing, The MIT Press, Cambridge, MA.

Lyons, J., (1985), Fire, ScientificAmerican. Inc., NewYork, NY.

American Institute of Aeronautics and Astronautics(1981), Combustion Experiments in a Zero-gravityLaboratory. New York, NY

PeriodicalsChandler, D., (1991), “Weightlessness andMicrogravity,” Physics Teacher, v29n5, pp.312-313.

Cornia, R., (1991), “The Science of Flames,” TheScience Teacher, v58n8, pp. 43-45.

Frazer, L., (1991), “Can People Survive in Space?,”Ad Astra, v3n8, pp.14- 18

Howard, B., (1991), “The Light Stuff,” Omni, v14n2,pp. 50-54.

Noland, D., (1990), “Zero-G Blues,” Discover. vl1n5,pp. 7480.

Pool, R., (1989), “Zero Gravity Produces WeightyImprovements,” Science, v246n4930, p.580.

Space World, (1988), “Mastering Microgravity,”v7n295, p. 4.

Science News, (1989), “Chemistry: Making Bigger,Better Crystals,” v136n22, p.349.

Science News, (1989), “Making Plastics in Galileo’sShadow,” v136n 18, p.286.

USRA Quarterly. (1992), “Can You Carry YourCoffee Into Orbit?,” Winter-Spring.

Page 173: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades
Page 174: Microgravity - NASA · 2004-01-07 · Microgravity — A Teacher’s Guide with Activities in Science, Mathematics, and Technology, ii EG-1997-08-110-HQ, Education Standards Grades