Attitude-control rocket exhaust plume effects on spacecraft functional surfaces

Abstract

An analytical and experimental program was conducted to identify the contaminants that form during the pulse-mode operation of a liquid-bipropellant, attitude-control rocket engine to establish whether the trace metals found in the propellants exist in sufficient quantity to cause physical damage to spacecraft functional surfaces, and to attempt to show quantitatively the geometric boundaries of the continuum and free-molecular flow regimes found in the control-rocket exhaust plume. It was found that the principal contaminant produced was monomethylhydrazine nitrate. Analysis also indicated that the trace metals found in the propellants are capable of causing severe damage to spacecraft functional surfaces, particularly to Vycor optical windows. The phase of the study devoted to flowfield analysis indicated that the interface between the continuum and free-molecular flow regimes can be quantitatively identified through a determination of the rotational and translational freezing surfaces.