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Skyler4856

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Anybody know where the "best" part of the atmosphere to renter is (or at least best place to burn off the most velocity)?   Is it the mesopause (lowest temperature, about 200K) or the stratopause (higher temperature ~275K, but more than twice the pressure).  I suspect the stratopause, considering that all that heat comes from adiabatic heating.  If they reach nearly the same pressure, you will be cooler in the stratopause (don't know if they will reach the same pressure).   Or do you often have somewhere between each the "best" place?

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2 hours ago, wumpus said:

Anybody know where the "best" part of the atmosphere to renter is (or at least best place to burn off the most velocity)?   Is it the mesopause (lowest temperature, about 200K) or the stratopause (higher temperature ~275K, but more than twice the pressure).  I suspect the stratopause, considering that all that heat comes from adiabatic heating.  If they reach nearly the same pressure, you will be cooler in the stratopause (don't know if they will reach the same pressure).   Or do you often have somewhere between each the "best" place?

Depends. Are you more worried about g-loading or shedding heat?

If it's heat you are worried about, go steep and get to the thicker air ASAP, but accept you will get massive g-loading. You'll dump your energy quickly, which will mean you shed your heat before a lot of it can transfer to the re-entry vehicle.

If g-loading is a concern, go shallow. But in that case, you'll experience a much longer time in the heating window, which will transfer more heat to your re-entry vehicle (so you need better heat shielding).

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On 1/28/2020 at 4:29 PM, wumpus said:

Anybody know where the "best" part of the atmosphere to renter is (or at least best place to burn off the most velocity)?   Is it the mesopause (lowest temperature, about 200K) or the stratopause (higher temperature ~275K, but more than twice the pressure).  I suspect the stratopause, considering that all that heat comes from adiabatic heating.  If they reach nearly the same pressure, you will be cooler in the stratopause (don't know if they will reach the same pressure).   Or do you often have somewhere between each the "best" place?

Re-entry is so energetic that temperature of atmosphere makes almost no difference at all. Only density. All of the interesting things are happening in the shockwave, and its temperature is basically determined by density and speed of the craft. Shape also plays a role there, but maintaining a dense, slow moving (relative to the craft) shockwave far ahead of the shield is more important, so blunt shapes are practically universal. @mikegarrison covered the rest in his reply.

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