Atul Kumar Presentation Week 3: February 1 st , 2007
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AAE450 Senior Spacecraft Design
Atul KumarPresentation Week 3: February 1st , 2007
Aerodynamics Team
Re-Entry vehicle analysis - Lifting body
1
AAE450 Senior Spacecraft Design
Mass calculationsMass components
Unit (M/T)
Payload 734.0506
Propellant 66.580
Structural mass w/o heat shield
42.169
Heat shield mass (underestimate)
~ 6.3085
Total Mass 849.1081
Heat shield mass based on a rough estimate made by the Thermal team’s - 20 kg/m^2 for the Mars Lander vehicle.
Mass and Volume of the payload.For transfer from HMO to the surface of Mars
at the end of 2nd synodic period. Carrying Habitat 2, Mars taxi 2, an ISPP and a taxi capsule
AAE450 Senior Spacecraft Design
Peak aerodynamic load (Gmax)
2
g’s experienced by the vehicle versus flight path angle
Max g’s experienced by the vehicle at an assumed entry speed of 7620 m/sec or Mach~ 33 from a height of 10.8 km above the Martian surface.
7620 m/sec is the speed of the space shuttle at entry.
AAE450 Senior Spacecraft Design
Geometry of the vehicle
Generalized geometry of a hypersonic vehicle.Figure based on book by Hankey, Wilbur L. Reentry Aerodynamics et al. ref 1
3-D drawing of the proposed reentry vehicle.
Drawn by Atul Kumar
AAE450 Senior Spacecraft Design
Backup slides
AAE450 Senior Spacecraft Design
Plots
Ballistic coefficient, β versus L/D ratio
/total dm C S
L/D versus Angle of attack
The two most aerodynamic characteristics, L/D ratio and the Ballistic coefficient define the undershoot boundary. Once the entry vehicle design requirements and crew load tolerances are computed, the entry flight path angle needed to
limit undershoot can be computed. The undershoot boundary defines the constraints for heat load or g-limit.
AAE450 Senior Spacecraft Design
Calculations2
max sin( ) /(2 )e e e sG V eg H
e - flight path anglee - 2.71828ge- Gravitational constant, 9.81m/sec^2Hs- scale height of Mars atmosphere, 10.8km
e
Ve- entry speed taken 7620 m/sec
Gmax = 7620^2*sin(10*pi/180)/(2*2.71828*9.81*10800) = 17.5050 m/sec^2
/( )total dm C S
Mtotal – total mass of the vehicleCd – coefficient of dragS – Reference area
AAE450 Senior Spacecraft Design
Plots
0 2000 4000 6000 8000 10000 12000235.2
235.4
235.6
235.8
236
236.2
236.4
236.6
236.8
Tem
pera
ture
, K
Altitude, m0 2000 4000 6000 8000 10000 12000
300
400
500
600
700
800
900
1000
Pre
ssur
e, P
a
Altitude, m0 2000 4000 6000 8000 10000 12000
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Den
sity
, kg
/m3
Altitude, m
Variation of temperature, pressure and density in Mars atmosphere with altitude
MARS AtmosphereVariation of Temperature, Pressure and Density of the Mars atmosphere
with altitude
AAE450 Senior Spacecraft Design
Computer codes
Code to compute the properties of Martian Atmosphere. Pressure, temperature, density and acceleration due to gravity as functions of height.
AAE450 Senior Spacecraft Design
Plots
Deceleration of the vehicle versus flight path angle
Well sustained crew can withstand a maximum deceleration of 12 g’s for a short period of time. And for a deconditioned crew this limit is between 3.5- 5g’s.
- Too little deceleration can cause the vehicle to skip off the planet’s atmosphere like a bouncing rock and too much deceleration can cause excessive heating and can damage the vehicle and jeopardize the crew’s safety.
AAE450 Senior Spacecraft Design
0 10 20 30 40 50-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Angle of Attack, AOA (deg)
Coe
ffic
ient
of
lift,
Cl
0 10 20 30 40 500.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
Angle of Attack, AOA (deg)
Coe
ffic
ient
of
drag
, C d
Plots for variations of coefficients of drag and lift with angle of attack
Plots
AAE450 Senior Spacecraft Design
Equation used to computeCl and Cd
Equations taken from the book Re-entry Aerodynamics, ref 1
AAE450 Senior Spacecraft Design
Contd
AAE450 Senior Spacecraft Design
Drawings
Different types of aerodynamic ManeuversFigure based on book by Larsonand Pranke et al. ref 2
AAE450 Senior Spacecraft Design
Drawings
Entry CorridorFigure based on book by Larsonand Pranke et al. ref 2
AAE450 Senior Spacecraft Design
References• Hankey, Wilbur L., Re-Entry Aerodynamics Chapter-3 Hypersonic Aerodynamics, pgs 70, 71, 72 & 73
• Larson, Wiley J., Pranke Linda K. Human Spaceflight Mission Analysis and Design, pgs 279, 314-315• Schneider, Steven P Methods for analysis of preliminary Spacecraft Designs, September 19th 2005
• Lessing, Henry C. Coate, Robert E., A Simple Atmosphere Reentry Guidance Scheme For Return From The Manned Mars Mission
• Griffin, Michael D. , French, James R. Space Vehicle Design, Chapter 6- Atmospheric entry, section -1, pg 231
• Anderson, John D., Jr. Fundamentals of Aerodynamics, chapter 14.
• Technical overview of the space shuttle orbiter http://www.columbiassacrifice.com/&0_shttlovrvw.htm
• Mars Fact sheet www.spds.nasa.gov/planetary/factsheet/marsfact.html+surface+density+of+mars&hl=en&gl=us&ct=clnk&cd=
• NSTS 1988 News Reference manualhttp://science.ksc.nasa.gov/shuttle/technology/sts-newsref/stsref-toc.html
• Wikipedia, www.wikipedia.org
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