Nozzle Plume Impingement on Spacecraft Surfaces: Effects of Surface Roughness (POSTPRINT)
UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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An experimental and numerical effort was undertaken to assess the effects of a cold gas T0-300 K nozzle plume impinging on simulated spacecraft surfaces. The nozzle flow impingement is investigated experimentally using a nano-Newton resolution force balance and numerically using the Direct Simulation Monte Carlo DSMC numerical technique. The Reynolds number range investigated in this study is from approximately 2 to 350 using nitrogen propellant. The thrust produced by the nozzle was first assessed on a force balance to provide a baseline case. Subsequently, aluminum plates were attached to the same force balance parallel to the plume flow to simulate spacecraft surfaces in proximity to the thruster. Three plates were used in this study, an electropolished plate with smooth surface, and two rough surface plates with equally spaced rectangular and triangular grooves. A 15 degradation in thrust was observed both experimentally and numerically for the plate relative to the free plume expansion case. The effect of surface roughness on thrust was found to be small due to molecules backscattered from the plate to the nozzle plenum wall. Additionally, the influence of surface roughness in the diverging part of the nozzle on thrust was examined numerically and found to be significant at Reynolds numbers less than 10.
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