Characteristic Motion of Entry Vehicles

Compared to (conventional) aircraft entry vehicles have not only a completely different mission profile, but also significantly different characteristics. Vehicles like the Space Shuttle, for instance, have a geometrical design that is optimised for the hypersonic flight regime, whereas the cruise characteristics in the high subsonic regime determine the configuration of conventional aircraft to a large extent. The situation for entry vehicles deviates even further if the vehicle is not aircraft-like such as the Shuttle, but a capsule such as the Apollo Command Module. The aerodynamic characteristics cannot even be compared anymore and also the means of control is completely different: Apollo only had a reaction control system (RCS) to counteract disturbances and lacks the aerodynamic control surfaces of aircraft and winged re-entry vehicles.