Hi argargreg,
I'm not entirely clear about what you want to test but...
Orbiter simulates orbital dynamics and aerodynamics (not material physical properties as such).
Orbiter's model of Mars atmosphere is pretty good I think, but I can't see any documentation about it in the Orbiter docs.
You could, for example, specify properties of your "Rover EDL Capsule" such as mass, cross section area, lift and drag coeffiecients. Orbiter will then be able to return such data as airspeed, altitude, atmospheric pressure/density, dynamic pressure, etc. You could calculate heating,stress,etc. on the basis of this I think.
However, you would need to program your own "Vessel" or "MFD" .dll to record and output the values.
Take a look at the Orbiter/OrbiterSDK/Doc/API_Guide.pdf to get an idea of how it works.
If English is your native language, you may like to inquire about this on the Anglophone forum
www.orbiter-forum.comRegards,
Brian