Estimation of Errors in Calculated Liquid Rocket Injector Performance Using a Miniature Cryogenic Test Stand

Abstract

Liquid oxygen and liquid methane rocket engines are leading candidates for a variety of space missions, including the critical role of main descent propulsion of planetary landing spacecraft. Particular mission characteristics in this context may dictate the use of propulsion systems with deep-throttling capability and able to deliver good performance over the entire thrust range. A well-known injector type with favourable combustion stability, heat transfer and performance characteristics is the pintle injector. This atomizer has been tested with a variety of propellants, such as monomethyl hydrazine/nitrogen tetroxide, fluorine/methane and oxygen/hydrogen. However, characterization employing liquid oxygen and liquid methane is relatively scarce. In order to obtain relevant parametric performance data at nominal and o-nominal conditions, a miniature cryogenic test stand operating with LO₂/LCH₄ propellants was designed and built. Presented here are the results of a systematic study to determine the uncertainty of measured and calculated parameters defining pintle injector performance. The approach used for the measurement of relevant quantities such as thrust, propellant flow rates, temperature and pressures is discussed and a description of the methodology used in the error analysis is given. Final values of uncertainty in characteristic velocity eciency are presented for dierent pintle injector configurations.