AAE450 Senior Spacecraft Design
Atul Kumar
Presentation Week 3: February 1st , 2007
Aerodynamics Team
Re-Entry vehicle analysis - Lifting body
1
AAE450 Senior Spacecraft Design
Mass calculations
Mass
components
Payload
Unit (M/T)
734.0506
Propellant
66.580
Structural mass
w/o heat shield
42.169
Heat shield mass
(underestimate)
Total Mass
~ 6.3085
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)
 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.
g’s experienced by the vehicle versus flight path angle
2
AAE450 Senior Spacecraft Design
Geometry of the vehicle
3-D drawing of the proposed
reentry vehicle.
Drawn by Atul Kumar
Generalized geometry of a hypersonic vehicle.
Figure based on book by Hankey, Wilbur L. Reentry Aerodynamics et al. ref 1
AAE450 Senior Spacecraft Design
Backup slides
  mtotal / Cd S
AAE450 Senior Spacecraft Design
Plots
L/D versus Angle of attack
Ballistic coefficient, β versus L/D ratio
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
Calculations
Gmax  Ve2 sin( e ) /(2eg e H s )
 e - flight path angle
e - 2.71828
ge- Gravitational constant, 9.81m/sec^2
Hs- 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
  mtotal /(Cd S )
Mtotal – total mass of the vehicle
Cd – coefficient of drag
S – Reference area
AAE450 Senior Spacecraft Design
Plots
Variation of temperature, pressure and density in Mars atmosphere with altitude
236.8
236.6
1000
0.02
900
0.018
800
0.016
236.4
236
Density, kg/m 3
Pressure, Pa
Temperature, K
236.2
700
600
0.014
0.012
235.8
500
0.01
400
0.008
235.6
235.4
235.2
0
2000
4000 6000 8000 10000 12000
Altitude, m
300
0
2000
4000 6000 8000 10000 12000
Altitude, m
0.006
0
2000
4000 6000 8000 10000 12000
Altitude, m
MARS Atmosphere
Variation 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
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.
Deceleration of the
vehicle versus flight path angle
AAE450 Senior Spacecraft Design
Plots
0.4
0.55
0.35
0.5
0.45
d
0.25
Coefficient of drag, C
l
Coefficient of lift, C
0.3
0.2
0.15
0.1
0.05
0.35
0.3
0.25
0.2
0.15
0
-0.05
0.4
0.1
0
10
20
30
40
Angle of Attack, AOA (deg)
50
0.05
0
10
20
30
40
Angle of Attack, AOA (deg)
50
Plots for variations of coefficients of drag and lift with angle of attack
AAE450 Senior Spacecraft Design
Equation used to compute
Cl 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 Maneuvers
Figure based on book by Larsonand Pranke et al. ref 2
AAE450 Senior Spacecraft Design
Drawings
Entry Corridor
Figure 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 manual
http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/stsref-toc.html
•
Wikipedia, www.wikipedia.org
7