Atmospheric penetration of exhaust plumes under rarefied flow conditions

The interaction of a low-density atmosphere with the exhaust gases produced by the steady firing of a rocket motor moving at hypersonic speed is studied using the kinetic theory of gases. The Krook collision model is employed in conjunction with a simple representation of the exhaust gas distribution to derive analytical and numerical solutions for the atmospheric gas density as it penetrates the rocket plume. The atmosphere gas is composed of an initially unscattered beam, which is attenuated as it collides with the much denser exhaust plume, and a scattered component, which is convected away from the motor by the expanding jet. These processes are illustrated by the computed results for both an axially symmetric and a three-dimensional flow.