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Unformatted text preview: ) () To determine the stagnation temperatures, we assume adiabatic flow and use
[ ( ) ()
()
()
()
The stagnation temperature is comparable to the boiling point (100 C) of water at sea level but much
lower than the maximum temperature (500F) of a typical home oven.
PROBLEM 3c
For a return capsule descending at M=35:
From Appendix E, for hg=150,000ft,
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()
() () To determine the stagnation temperatures, we assume adiabatic flow and use
[ ( )
()
()
() ( ( ) ) ()
The stagnation temperature is about 680 times higher than the boiling point (100 C) of water at sea level
and roughly 250 times the temperature (500F) of a typical home oven. The stagnation temperature of
the vehicle on reentry by our calculations is much higher than the temperature (5800 K) of the Sun’s
surface.
Our calculations are inaccurate. The stagnation temperature is determined with the assumption that the
flow is adiabatic. Upon reentry, the surface of the return capsule would radiate high amounts of
thermal energy. Also at high temperature the gas would dissociate or even form a plasma. Much of the
energy is absorbed by tearing molecules apart. The value calculated by assuming adiabatic flow and a
perfect gas with constant specific heats is a gross overprediction. The actual temperature at the
stagnation point will be lower than our prediction....
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 Spring '09
 COLLICOTT

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