Pulse Performance Analysis of a 45 Newton Additively Manufactured Bipropellant Thruster

Abstract

This paper describes the testing and pulse performance analysis of a 45 N thruster, designated A45, using a 19.78% monomethylhydrazine–80.22% hydrazine fuel blend with mixed oxides of nitrogen containing 3% nitric oxide as the oxidizer. The thruster components are fabricated using additive manufacturing (AM), which enabled fine design features on injectors to achieve fast response times. The main focus of this work is to demonstrate precise and repeatable pulse performance and combustion stability and to compare thruster performance with theoretical predictions from NASA CEA across the chosen test matrix. As part of the pulse performance analysis, impulse produced by each pulse of a given 50 Hz pulse train is characterized, thereby illustrating that true pulse repeatability on such thrusters only starts with the third pulse. This is caused by the priming of the injector manifold at the start of a pulse train. Specific impulse as functions of pulse ON and OFF times are also characterized for a 50 Hz duty cycle and dry injector manifold operation. This method of per-pulse performance characterization aids guidance, navigation, and control teams in thrust/impulse control for attitude control. Overall, the specific impulse, characteristic velocity efficiency, and response times demonstrated by this additively manufactured thruster are similar to those fabricated by traditional methods and support wider use of AM in the aerospace industry.