Continuum and Kinetic Simulations of Orion (CEV) Atmospheric Re-entry in High Altitude Flight Conditions

The high Knudsen number aerothermodynamics and the evaluation of effects of gas rarefaction in prediction of the main aero-thermal loads of Crew Exploration Vehicle (CEV) is presented and analyzed. The focus of this investigation is to provide information where overlap between continuum approach and particle one occurs. It is well known that the Navier-Stokes equations fail in rarefied regimes and a molecular approach such as the Direct Simulation Monte Carlo method (DSMC) is necessary. Slip flow boundary conditions have been implemented in CIRA CFD code H3NS in order to verify the extension of validity of a continuum method in the transition flow regime. Sensitivity of results to surface boundary conditions is presented.