An investigation of preferential interfacial reactions in nonmetalized composite solid propellant combustion

Abstract

Four nonraetalized solid propellants were burned at 500 psi in strands of 1/2 in. by 1/2 in. cross section and 2 in. length in both a dewetted and an as-cast state. Strands were burned at acceleration levels from zero to lOOOg normal and into the burning surface, and 50g and lOOOg normal and out of the burning surface. The effects of changing interfacial characteristics of the oxidizer and binder by prestressing (dewetting) were studied to determine if preferential interfacial reactions between binder and oxidizer particles provided an accurate explanation of burning rate augmentation. Preferential interfacial reactions did not exist in the propellents studied at the pressures and accelerations at which the investigation was made. Soft binders in nonmetalized propellants were found to allow oxidizer-binder Interaction at high accelerations resulting in unstable combustion and self-extinguishment. Nonmetalized composite propellants that did not contain opacifiers appeared to burn more erratically in a positive acceleration environment.