Aerodynamic Interactions of Reaction Control System Jets on Mars Entry Aeroshells

Abstract

The fluid interactions produced by a sonic reaction control system (RCS) thruster for a Mars-entry aeroshell are investigated using computational fluid dynamics (CFD). The study uses a scaled Mars Science Laboratory (MSL) aeroshell at a 20 • angle-of-attack in Mach 12 flow of I2-seeded N2 gas. The RCS jet is directed either parallel or transverse to the freestream flow in order to examine the effects 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 flow 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 fluid interactions produced by the parallel and transverse jets affect the control effectiveness 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 deficit of control authority. The physical accuracy of the computational method is assessed by comparing the numerical results with experimental visualizations.

Numerical Analysis of Surface Chemistry in High-Enthalpy Flows

“…LeMANS can simulate twodimensional/axisymmetric flows using any mixture of quadrilaterals and triangles, as well as three-dimensional flows using any mixture of hexahedrals, tetrahedrals, prisms, and pyramids. The code has been extensively validated for hypersonic flows [30][31][32][33].…”

Planar Laser Induced Iodine Fluorescence for the Investigation of the Aerodynamics of Reaction Control System Jets on Mars-Entry Aeroshells

“…Breakdown would occur for Knudsen values >0.05. Calculating this number for the experiment conditions, the continuum assumption has been determined to be valid for the RCS jet interaction [49,107].…”

“…Ideally, this number is one, indicating the thrust performs as expected. Alkandry found that the parallel RCS jet does indeed have a control gain of 1.0, indicating ideal control effectiveness but that the transverse jet resulted in a control deficit [107,110]. For the parallel jet, the axial and normal components of thrust contribute to a net positive moment of thrust but the transverse produces one component with a positive moment and one with a negative moment, resulting in a net reduced moment from thrust, with respect to the center of gravity.…”

“…Plus, the parallel jet had a longer moment arm than the transverse jet so that the parallel jet had a more effective thrust moment [110]. Another reason the transverse jet has reduced control gain is due to the higher interference moment than the parallel jet, which augments pressures on the surface of the aeroshell, creating counteracting moments in the wake region [107,110]. At higher thrust coefficients for the transverse jet, the counteracting moments cancel each other more than at lower thrust coefficients, resulting in an improvement in control.…”

Investigation of Hypersonic Retropropulsion Using Planar Laser-Induced Iodine Fluorescence

“…Limiting factors, such as the inability to scale supersonic parachutes to adequate size, coupled with the desire to send manned missions to Mars (with landed masses estimated at 20-100 metric tons), [19][20][21][22] has prompted renewed interest in experimental and computational efforts to better understand the highly complex flow properties of SRP and HRP. 10,11,[23][24][25][26][27][28][29][30][31] Experimental efforts by validation and verification quality data and study the unsteady effects of the flow which has been reported. 10 Testing was carried out at NASA Langley's Unitary Plan Wind Tunnel for a 5-inch model at Mach 2.4, 3.5, and 4.6 using pressure taps, several of which are capable of 40 kHz measurements, thermocouples, and high speed schlieren.…”