Performance Evaluation Of Combustion-Controllable 0.1-N-Class Solid Propellant Microthrusters Using Laser Heating

Conventional solid-propellant thrusters do not require tanks or valves and, accordingly, have high reliability and simple structures. Nevertheless, thrusters have not been applied to the attitude or station control of satellites because of problems with throttling. We therefore propose a new combustion-controllable, solid propellant microthruster using laser heating. The proposed thruster uses combustion-controllable, hydroxyl-terminated polybutadiene/ammonium perchlorate solid propellant where combustion is maintained only while the burning surface is heated with a laser. Therefore, combustion is started and stopped by switching the laser heating. In a previous study, laser-switching was used to start and stop thrust production. Stable thrusts and combustion chamber pressures with a thrust and specific impulse I-sp of 0.02N and 95 s, respectively, were obtained. However, firing tests showed an ignition delay of approximately 3 s. In this study, to shorten the ignition delay, the diameter of carbon black (C) used to absorb the laser beam was reduced from 50 to 20 mu m. Thrust measurements showed that a phi 20-mu m C was comparable to a phi 50-mu m C in terms of the maximum I-sp, and reduced ignition delay. Using a phi 20-mu m C produces a shorter ignition delay and 120-s-class I-sp by adjusting the laser-head traverse velocity.