Suppression of Hard Start for Nontoxic Hypergolic Thruster Using H2O2 Oxidizer

The present paper describes the phenomenon of hard start observed from a demonstrator of 500N scale nontoxic hypergolic thruster using high-test peroxide as an oxidizer. When 90% concentration of hydrogen peroxide was used, the hard start was observed even under the fuel lead operation. To effectively suppress the occurrence of hard start phenomena in the startup phase of the thruster, oxidizer-to-fuel mass ratio and concentration of hydrogen peroxide have been individually considered. In drop tests, the ignition delays of hypergolic reactions became longer in the oxidizer-rich condition than those measured in the fuel-rich condition. By regulating oxidizer-to-fuel mass ratio with deliberate control of the oxidizer mass flow rate, the thruster operated smoothly even using 90% high-test peroxide in the fuel-rich environment. Furthermore, without the utilization of the flow control device, the thruster successfully operated when higher concentrations of high-test peroxide (95 and 98%) were used under the fuel-rich condition.