Propulsion Deceleration Studies using Planar Laser-Induced Iodine Fluorescence and Computation Fluid Dynamics

Abstract

Future high-mass spacecraft entering the thin Martian atmosphere will require additional means of deceleration prior to deploying supersonic parachutes. Propulsive deceleration is one technology that is being considered. The interaction of the spacecraft aerodynamics with the propulsion deceleration (PD) jets has been shown to cause a decrease in drag coefficient with increasing thrust coefficient, which is not desirable for deceleration. Planar LaserInduced Iodine Fluorescence (PLIIF) images showed a lifting of the vehicle bow shock away from the aeroshell. Flowfield calculations performed using a CFD code showed that this lifting was responsible for the decrease in drag with increasing PD jet thrust. With 4 PD jets located midway between the aeroshell centerline and shoulder, PLIIF images showed that the vehicle bow shock is maintained between the jets as the thrust coefficient is increased. CFD calculations established that this bow shock was responsible for greater drag preservation with the peripheral jets. The peripheral jet drag coefficient was 4 times larger than the single jet value at a thrust coefficient of 2.0. The calculations also showed low pressure wakes located radially behind the peripheral jets which are responsible for the decrease in drag coefficient with increasing thrust coefficient and that high pressure is maintained between the jets. These results suggest that using a few peripheral PD jets located near the aeroshell shoulder would provide the greatest amount of drag preservation when using propulsive deceleration. Nomenclature