Interactions of Single-Nozzle Sonic Propulsive Deceleration Jets on Mars Entry Aeroshells

Abstract

The effects of the propulsive decelerator (PD) jet Mach number on the flowfield, surface, and aerodynamic properties of a Mars entry aeroshell are investigated in Mach 12 laminar fl ow of I 2-seeded N2 gas. This is achieved using the computational fluid dynamics (CFD) code LeMANS, as well as the planar laser-induced iodine fluorescence (PLIIF) experimental technique. The results show that the flowfield features, such as the standoff distance of the bow and jet shocks, are all affected by the PD jet Mach number. The results also show that as the thrust coefficient increases, the flow around the aeroshell approaches a jet-only, no freestream configuration due to a PD jet shield. Therefore, the effects of the PD jet Mach number on the surface properties and the drag coefficient increases. As a result, the difference in the drag coefficient between the supersonic and sonic jets increases to as much as 25%. However, since the drag is inversely proportional to the nozzle thrust, the total axial forces for the supersonic and sonic jets are in close agreement, with a maximum difference of 4%. This result indicates that the overall deceleration performance of the aeroshell is only slightly affected by the PD jet Mach number for these particular conditions. The study also shows that propulsive deceleration with central PD jets may only be beneficial for thrust coefficients greater than 1.5 for both sonic and supersonic jets; a result that appears to be independent of the jet exit Mach number. Finally, qualitative comparisons between LeMANS and PLIIF show overall good agreement in the bow shock profile and standoff distance.