Combustion mechanism of an RDX-based composite propellant

The combustion mechanism of a composite propellant having the nominal compo sition 84% RDX + 16% HTPB has been investigated experimentally. The followi ng steady combustion parameters were collected over the pressure range 0.1 to 8.21 MPa: burn rates, burn surface temperatures, thermal gradients, heat release in the condensed phase, heat feedback from the gas phase, first an d second (or final) flame temperatures. In general, for the tested RDX.HTPB mixture,values smaller than the corresponding AP.HTPB parameters are found , while the burning rate pressure exponent is larger. Likewise, the measure d values are smaller than the corresponding pure RDX parameters when HTPB b inder is added; a notable exception is the heat release in the condensed ph ase, which is larger. The obtained dependence of burn rate on burn surface temperature fits the unified gasification law for nitramines. Thus, RDX see ms to dictate its macrokinetics law upon the HTPB gasification. The main pr ocesses taking place simultaneously at the burn surface are: gasification a nd thermal decomposition of RDX, as well as oxidation of part of the HTPB b inder, probably due to liquid-phase mixing between molten ingredients. (C) 1999 by The Combustion Institute.