Solid propellant combustion under laser heating

This paper describes experimental work on control of solid propellant combustion with laser heating. Burning rates of HTPB/AP composite solid propellants were measured at pressures up to 200 kPa with laser power densities up to 2.1 W mm. With our (fuel-rich) non-self combustible solid propellants, the combustion control, including ignition and interruption by switching on/off the laser, was feasible, and the burning rate coincidentally obeyed Vieille’s law with pressure exponents of approximately 0.3. Hence, this combustion control with the laser irradiation seems to be applicable to space propulsion for microsatellites. The heat feedback rate from flame to burning surface, Hf, was estimated from the burning rate variation with laser power density. In case with the fuel-rich solid propellant, Hf increased from 2 to 7 W mm in keeping with back pressure from 30 to 200 kPa. This suggests that approximately 70% of the energy to the burning surface is provided by the combustion itself, and the rest 30 % is supplied by the laser as the supplementary heat flux to compensate for the heat insufficiency for combustion sustenance.