Combustion of RDX/AP composite propellants at low pressures

Abstract

The burning rate characteristics of RDX (cyclotrimethylene trinitramine)/AP (ammonium perchlorate) composite propellants were intermediate between the characteristics of RDX and AP composite propellants. Fine thermocouple traverses in the combustion zones revealed that the flame structure of the RDX/AP propellants consists of two types of flames: one type is the diffusion flame streams produced by the decomposed gases of the AP particles and the binder; the other type is the premixed flame produced by the decomposed gases of the RDX particles and/or the binder. Thus, the flame structure above the burning surface appeared to be very heterogeneous. The heat feedback from the gas phase to the burning surface was significantly reduced by the reduced reaction rate of the RDX premixed flame. Therefore the burning rate of the RDX/AP propellants was lower than that of the AP propellants. The burning rate of the RDX/AP propellants was also affected by the type of binder used. The effect of the binder on the physical and chemical processes of the RDX/AP propellant burning was the alteration of the burning surface structure and the alteration of the burning rate of the AP particles in the propellants.