Effect of Freestream-Plume interaction on launch vehicle aerodynamics

The pitch and yaw plane characteristics of a launch vehicle due to interaction of hypersonic freestream (Mach 5) with supersonic plumes (Mach 3.2) were experimentally studied on a scaled model through wind-tunnel tests. Towards this, a model was designed to accommodate a conventional strain-gauge balance to measure aerodynamic coefficients due to interaction alone. A finite element analysis was carried out to ascertain the design is proper. Schlieren images were captured to understand the complex flow features. In the pitch plane, C_N,C_m(nose),and CA, were reduced by 11.3, 24.3, and 69% owing to freestream-plume interaction. A stabilizing effect was observed as a result of increasing angles of attack, irrespective of whether the plume is on or off. At discrete angles of attack, the introduction of plumes resulted in destabilizing effects. In the yaw plane, the freestream-plume interaction reduced CS and C_n(nose)by 9.1 and 15%. An increase in the sideslip angle and the introduction of plumes resulted in a stabilizing effect.