Model for Melt-Layer Front in Ammonium Perchlorate Propellant Combustion

In solid rocket-propellant combustion, the dynamic phase change from condensed to gas occurs across the melt layer. During the surface burning, liquid and gas phases are mixed in the intermediate zone between the propellant and the flame to form microscale bubbles. The known thickness of the entire melt layer is approximately 1 μm at 10 5 Pa and 0.1 μm at approximately 10 7 Pa for ammonium-perchlorate/hydroxy-terminated polybutadiene propellant. In this paper, a model of the melt-layer front between the condensed and gaseous phases and the dynamic motion of the melt-layer front derived from the classical phase-field theory is presented. The model results show that the melt-layer front grows and propagates uniformly according to exp(―1/T s ), with T, being the propellant surface temperature.