TRANSTAGE INJECTOR FROSTING INVESTIGATION UNDER VACUUM CONDITIONS

This report is concerned with the effects of propellant frosting of large space engine injectors under vacuum conditions. This effect is a result of propellant valve leakage into the injector assembly at various injector temperatures, during an engine coast period. A transtage injector was used for the subject investigation and the tests were conducted at altitudes between 400,000 and 500,000 feet. The test propellant was 50% UDMH - 50% N2H4 and the valve leakage rate was 100 cc/sec. The analysis of data derived from this effort has clearly shown that the rate and amount of propellant frost accumulation within the injector assembly, as well as on the face of the injector and baffles, increases with decrease in the initial injector assembly temperature. In addition, this frost accumulation is further magnified when the leakage duration is increased. (Author)