On the Microstructure of Composite Propellants

Abstract

The term composite propellant as commonly used in the solid rocket industry refers to a heterogeneous mixture of several phases of solid particles entrained in a rubberlike binder. The two principal solid phases are aluminum fuel and ammonium perchlorate oxidizer; together with a small amount of additives which control adhesive and ballistic properties, they constitute the filler. Either a branched polyurethane or crosslinked polybutadiene network serves as a typical binder. Performance calculations based on the assumption that the enthalpy of the composite balances the enthalpy of the combustion products at their flame temperature lead to the demand for a composite filled with slightly more than 88 wt. % of solid phases, about 25% of which is aluminum. At this point a little arithmetic is in order.