Aerodynamics of the Mars Microprobe entry vehicles

The selection of the unique aeroshell shape for the Mars Microprobes is discussed. A description of its aerodynamics in hypersonic rarefied, hypersonic continuum, supersonic, and transonic flow regimes is then presented. This description is based on direct simulation Monte Carlo analyses in the rarefied flow regime, thermochemical nonequilibrium computational fluid dynamics in the hypersonic regime, existing wind-tunnel data in the supersonic and transonic regime, additional computational work in the transonic regime, and, finally, ballistic-range data. The aeroshell is shown to possess the correct combination of aerodynamic stability and drag to convert the probe's initial tumbling attitude and high velocity at atmospheric interface into the desired surface-impact orientation and velocity.