Space Colonization Terra-forming

Space Colonization

Terra-formingASTR 1420

Lecture 25

Not in the Textbook

Space Colonization

Space colonization in this lecture is in a narrow sense : colonization by human and in the Solar System only (say within next few millennia).

• Also known as space settlement, space habitation, etc.

Space colonization = self-sufficient human habitation outside the Earth

o on planetso on satelliteso free spaceo outside of the Solar System

Reasons why some humans living in Space• Survival of our species• $$$ : solar power satellites, asteroid mining, space manufacturing, etc.• Resources : sufficient supply of rare materials• lesson the burden on the Earth• spread our beauty(?) to the Universe

“The long-term survival of the human race is at risk as long as it is confined to a single planet. Sooner or later, disasters such as an asteroid collision or nuclear war could wipe us all out. But once we spread out into space and establish independent colonies, our future should be safe.” Stephen Hawking

Insulin crystal growth in space (left) versus on Earth (right)

Space solar power station (immediate feature)A space-based solar power station will use an array of mirrors to concentrate the sun’s rays on photovoltaic cells. The electricity produced is converted into a powerful microwave beam directed at an antenna on Earth, where it is converted back into electricity and fed to the grid.

This simple design can generate 13.4 billion watts per second which is ~15 times more than annual energy consumption of USA

Things to be considered…

• mass per person• radiation shielding• minimum size• leakage rates• cost• schedule

Materials and Energy• using material from Earth is very expensive due to larger gravity of Earth.o Also, large-scale project will impact the Earth communityo Need to use materials from Moon, Mars, large asteroidshowever, these objects lack volatiles (Hydrogen and Nitrogen).solution? Jupiter’s Trojan asteroids have high content of water ice and other

volatiles.

• Solar energy is abundant in the space (no night, no cloud, no atmosphere).o Energy on the top of Earth Atmo. (watts/m2) = 1366 / d2, (d is distance in AU)o In developed countries, energy usage ~ 1000 watts/persono Export created energy back to Earth

• Mars and Moon colonies may need to use nuclear energyo waste heats? requires a large radiator!

Transportation and Communication• Transportationo expect millions of shuttle launches..

requires cheaper and less pollutant transportation devices.

o hypersonic spaceplane, space elevator, mass driver, etc.

o all other rocket technologies we studied last lecture!

• Communicationo for more distant colonies (e.g., Mars), a real

time communication is impractical due to the light travel time (7 – 44 minutes lag).

o email or voice mails…

• To prevent inbreeding reduced fertility, genetic disorders, infant mortality, malfunctioning immune system, etc.

• In 2002, anthropologist, John H. Moore.population of 150-180 would allow normal reproduction for 60—80 generations (~2,000 population for long survival).

• “50/500” rule: conservation biologists, 50 is the minimum to prevent an unacceptable rate of inbreeding, 500 is required to main overall genetic variability.

minimum “isolated” habitat population = 500

Minimum population size

Life support• We need air, water, food, mild temperature, and gravity.• In space, closed ecological systems must recycle (or import) resources

• Nuclear submarine : carry out missions for months without resurfacingo although they recycle oxygen, it is not “closed” system. o they extract oxygen from sea water and dump CO2 outside.

• Radiation protection: against harmful cosmic rays and solar wind. o Either we need 5—10 tons of blocking (absorbing) material per square

meter of surface habitat area. Or we can make the hull-metal electric to protect against charged particles.

o Two experiments in 1991 and 1994

Biosphere 2 : experiment of a “closed” ecosystem• Biosphere 2 in Arizonao a small, complex, manmade biosphere supported

8 people for 1+ years!o after 1 year, oxygen had to be replenished.

savana and ocean

coastal desert

crew quarters

Size of 2.5 football field. $200 million dollars. 1987-2007

Bernal Sphere• a type of space habitat intended as a long-term home for permanent

residents, first proposed in 1929 by John Desmond Bernal (Irish Scientist).

O’Neil’s habitat (1974)• Good locations are L4 & L5 points.

one of O’Neil’s three designs called “Island Three”: two very large, counter-rotating cylinders, each 5 miles (8 km) in diameter and 20 miles (32 km) long

Other variants

Toroidal and Spherical colonies. Bernal Spheres.

Objections• Even if the technology was available, and the costs of deploying a program

relatively low, and the likelihood of success relatively high, only a small number of people would directly benefit from a colony (either enthusiastic colonists or high risk commercial interests), leaving most of financial burden on the public.

• Humans are treated as assets

• If the main reason is “insurance” against the annihilation of human, then why people on Earth need to pay for something useful only after their deaths?

Counter arguments• argument of need

“population growth and limited resources on Earth” By 2040, population will be 10 billion!, gem stones, power, etc.

• argument of costCost of wars since 2001 = $1.32 trillion USD

• argument of benefitsdespite the high cost of initial investment…space colonies can provides precious metals, gem stones, power, etc. the smallest Earth-crossing asteroid 3554 Amun (~2km): iron, nickel, cobalt, platinum etc

(30x the amount ever mined. $20 trillion USD)

Terraforming

planetary engineering :

process of deliberately modifying atmosphere, temperature, surface topography, or ecology of celestial objects to fit our purposes

Terraforming Mars• Two things: atmosphere and heating

• Once it is terraformed to be similar to Earth, will it be able to sustain the condition over geological timescales (10s Myr to 100 Myr)?

• How ?o Small size is the main issue…

o Re-heating the core of Mars is considered an impractical solution

o the slow loss of atmosphere could possibly be counteracted with ongoing low-level artificial terraforming activities.

Method?• Put several, large solar mirrors to direct light to the Martian surface (to

increase T)

• Bring one of ice moons of Jupiter or Saturn induce an impact with an ~1,000 km object to melt the whole thing which will re-liquefy the core magnetic field!

Terraforming Venus

Requirements : • removing most of the

planet's dense 9 MPa carbon dioxide atmosphere

• reducing the planet's 450 °C (850 K) surface temperature

• Addition of O2

• Reduce the length of day(?) : 117 Earth days

How?

• Solar shade at L1• reflector on the ground

or in the atmosphere • use of genetically

engineered bacteria which can turn CO2 into other organics

• induce an impact with 500-700km asteroid (to eliminate atmosphere fast)

Europa • a good potential candidate for terraforming• One clear advantage of Europa is the

presence of liquid water

Difficulties• huge radiation (in the middle of Jupiter’s

radiation belt; On Europa, a human would die from the radiation within ten minutes on the surface)o require the building of massive radiation

deflectors, which is currently impractical• satellite is covered in ice and would have to

be heated• need for oxygen electrolysis of ocean water

In summary…

Important Concepts• Closed ecosystem experiments• Space habitat• Pros and cons of space habitats• Terraforming Mars, Venus, etc.

Important Terms• Terraforming• Biosphere 2• Bern sphere• ONeil’s habitats

Chapter/sections covered in this lecture : Not from the textbookHuman and Environment : next class!