Free molecular aerodynamics for satellite application

The aerodynamic actions on satellites in earth orbit are discussed. To establish the problems involved, a short summary of typical satellite geometries and the upper atmosphere's flow properties is given. Satellites are exposed to a free molecular flow of a gas mixture, the freestream molecular Mach number of the different components varying, according to molecular weight, between S sub infinity approximately equals 3 and 2O. As the flow is free molecular, each species develops its own independent flow field. Only one component of a mixture is considered. The free molecular flow theory is stated both for convex and concave structural elements of a satellite. For both cases the physical and theoretical flow behavior is investigated, and simplified solutions for limiting cases are developed. In addition, the resultant aerodynamic coefficients are calculated by exact and approximate methods for typical bodies and body elements.