Pressure oscillation amplification of pulse modulated monopropellant thruster

Abstract

Pulse modulation is a throttling method utilizing periodic open/closure of a valve to control propellant injection into the thruster. Pressure oscillation within the propellant feed line is created by the rapid operation of the valve. If surge pressure created in the previous cycle interacts with the pressure traces of the next, pressure oscillation can be amplified by acoustic resonance when operated at specific pulse conditions. This phenomenon was experimentally investigated using 50 N Hydrogen Peroxide monopropellant thruster operated at various frequency and duty cycle conditions. The results show that pulse conditions which trigger resonance can be identified using the response characteristic of the valve and the natural frequency of propellant feeding system. Under these conditions, intensified pressure oscillation within the propellant feed line induce excessive structural vibration of propellant feeding system which might lead to critical system failure.