The lateral surface drag coefficient of cylindrical spacecraft in a rarefied finite temperature atmosphere

In the present determination of the free molecule flow drag coefficient for a cylindrical spacecraft flying parallel to its principal axis, the lateral surface effects of thermal motion are explicitly included in terms of the average impact angle of the incident gas momentum vector. Kinetic theory is used to characterize self-shadowing, as well as to obtain an expression for the lateral surface coefficient in terms of the average impact angle of the incident momentum vector and the fractional momentum transfer along the line of impact. It is found that, for a length/diameter ratio of about 5, the lateral surface contribution to the drag coefficient is comparable to that of the front face.