Monte Carlo Simulation for Ambient Scatter of Outgassing Molecules from Cylindrical Spacecraft Surfaces

Abstract

The test particle Monte Carlo (TPMC) method for the prediction of the ambient scatter of outgassing molecules from spacecraft surfaces is presented, with a test case of an outgassing sphere to validate the method developed here. Then, the TPMC method is applied to a simplified cylindrical spacecraft outgassing surface, to investigate the effects of geometrical, freestream and outgassing conditions on the ambient-scatter returned flux ratio (RFR). It is observed that the returned molecules distribute mainly over the windward part of the side surface of the cylindrical surface. Besides, the variation of RFR takes on various numerical behaviors with different freestream and outgassing conditions, and it can be concluded that the length-to-radius ratio of the cylinder has a significant effect on the RFR.