Numerical Study of Facility Pressure Effects on Micronozzles for Space Propulsion.

This study used a direct simulation Monte Carlo approach to investigate the effects of facility pressure on micronozzles for the propulsion systems of microspacecraft. The simulations quantitatively evaluated the effect of background pressure on the micronozzle performance in nozzle flows ranging up to a throat Reynolds number of 220. The results showed that the background pressure could reduce total thrust by more than 50% as the inverse of the nozzle pressure ratio increases from 0 to 5.0×10-3. The primary cause identified was the gas depletion created by the collision of the nozzle plume with the background gas, which creates a negative thrust on the wall surface surrounding the nozzle. The trend of the background-gas-pressure effect differed at each Reynolds number. The wall size also affected the thrust in finite background pressure. Furthermore, this study emphasized the critical role of test-facility conditions in accurately predicting the performance of micronozzles and provided the knowledge necessary to properly predict their performance during space operations. [ABSTRACT FROM AUTHOR]