Numerical Investigation of Multi-Nozzle Propulsive Deceleration Jets for Mars Entry Aeroshells

摘要

The effects of peripheral propulsive decelerator (PD) jets on the deceleration performance of Mars-entry aeroshells are examined using the computational fluid dynamics code LeMANS and the planar laser-induced iodine fluorescence experimental technique. The study uses an aeroshell based on the Mars Science Laboratory with four peripheral jets in Mach 12 flow of l2-seeded N_2 gas. Sonic and supersonic peripheral jets are considered in this study. The results show that the peripheral PD jets increase the standoff distance and change the profile of the bow shock around the aeroshell. The results also show that PD jets obstruct the flow around the aeroshell, which creates a low pressure region on the surface behind the jets. The level of obstruction increases with thrust, which expands the low pressure region. As a result, the drag on the aeroshell is inversely proportional to the thrust. The PD jet Mach number, however, has a small effect on the deceleration performance, with a maximum difference of less than 2.5% in the axial force between sonic and supersonic peripheral jets. The study also compares the deceleration performance of peripheral PD jets to previously published results for central PD jets. The results show that the peripheral jets provide 3 to 8 times larger drag than central jets due to higher surface pressures. Finally, qualitative comparisons between the numerical results and experimental data show overall good agreement in the bow shock standoff distance and profile.