Aerodynamic Interactions of Reaction Control System Jets on Mars Entry Aeroshells

Abstract

The uid interactions produced by a sonic reaction control system (RCS) thruster for a Mars-entry aeroshell are investigated using computational uid dynamics (CFD). The study uses a scaled Mars Science Laboratory (MSL) aeroshell at a 20 angle-of-attack in Mach 12 ow of I2-seeded N2 gas. The RCS jet is directed either parallel or transverse to the freestream ow in order to examine the e ects of the thruster orientation with respect to the center of gravity of the aeroshell. The results show that both the parallel and transverse RCS jets obstruct the ow around the aeroshell and impinge on the surface, which increase the overall pressure on the aftbody. As a result, the RCS jet decreases both the drag and lift forces, and the moment acting on the aeroshell, particularly at relatively large RCS thrust conditions. The results also indicate that the uid interactions produced by the parallel and transverse jets a ect the control e ectiveness of the RCS. The performance of the parallel RCS thruster is close to ideal due to relatively small aerodynamic interference induced by the jet. However, the relatively large aerodynamic interference produced by the transverse RCS jet causes a de cit of control authority. The physical accuracy of the computational method is assessed by comparing the numerical results with experimental visualizations.