THERMOCHEMICAL NONEQUILIBRIUM EFFECTS ON THE AEROTHERMODYNAMICS OF AEROBRAKING VEHICLES

A three-dimensional computational fluid dynamics algorithm is develope d to study the effect of chemical and thermal nonequilibrium on blunt body aerodynamics. Both perfect gas and five species air reacting gas models are used to compute the flow over the Apollo command module. Th e reacting gas air mixture is assumed to be governed by a translationa l-rotational temperature and a vibrational temperature. The Navier-Sto kes computations are compared to wind-tunnel and flight-aerodynamic da ta from the Apollo missions. The effects of chemical reaction and vibr ational excitation on lift-to-drag ratio and trim angle are investigat ed. It is shown that including real gas effects results in a lower tri m angle and L/D than predicted by nonreacting gas wind-tunnel simulati ons. The reacting gas numerical results are consistent with flight dat a from the unmanned Apollo AS-202 mission, whereas the perfect gas com putations agree with the extrapolated preflight wind-tunnel results.