AAE450 Senior Spacecraft Design

Atul KumarPresentation Week 3: February 1st , 2007

Aerodynamics Team

Re-Entry vehicle analysis - Lifting body

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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)

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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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