Laser-Assisted Combustion of Solid Propellants at Low Pressures

Abstract

This paper describes experimental work on laser-assisted combustion and its use to control solid propellants. Burning rates of hydroxyl-terminated polybutadiene and ammonium perchlorate composite solid propellants were measured at pressures up to 90 kPa under laser irradiation, and propellant-preheat temperature distribution was measured by thermography. Combustion control, including ignition and interruption by laser irradiation, was feasible with custom-made (fuel-rich) non-self-combustible solid propellants with a burning rate coincident with Vieille's law and a pressure exponent of approximately 0.5. Consequently, this combustion-control concept seems to be applicable to a microsatellite thruster. The heat balance on the burning surface evaluated at a laser power density of 1.4 W ·mm -2 at 50 kPa produced the following results: chemical reaction was endothermic at a heat flux of -0.7W mm -2 , heat was supplied to the solid phase of the propellant at a heat flux of 3.7 W ·mm -2 , and heat-feedback rate to the burning surface was 3.0 W ·mm -2 , which suggests that approximately 70% of the energy transferred to the burning surface was provided by combustion itself, and the laser supplied supplementary heat flux to compensate for the heat insufficiency to sustain combustion.