Visualization of pulse firing mode in hypergolic bipropellant thruster

Mitsubishi Heavy Industries, Komaki 485-0826, Japan Abstract The pulse firing mode of bipropellant thrusters is crucial for the precise attitude control of spacecraft. This research explains how to simultaneously measure the chamber pressure and observe the combustion dynamics in the consecutive pulse firing of the monomethylhydrazine and the mixture of nitrogen tetroxide with approximately 3% nitric oxide bipropellant thruster. This study investigated transient behaviors in the ignition and cutoff of the pulse firing mode of the thruster. There was a delay in measuring the chamber pressure for two reasons: The time needed for the propellant to fill the manifold, and the delay in the response time of the pressure-sensing system. The time needed to fill the manifold depends on the pulse number, whereas the response time of the system factor is constant. This paper also demonstrates that a fuel-rich injection in the pulse firing mode leading to explosive ignition can be realized by prompt evaporation of the oxidizer from the manifold. Acknowledgments We wish to express our gratitude to all people involved in this research, especially the thruster test team members at the Isahaya site of Mitsubishi Heavy Industries.