Experiments relating to the combustion of ammonium perchlorate-based propellants

Abstract

Experiments designed to examine certain features of the combustion mechanism of ammonium perchlorate-based propellants are briefly discussed in relation to a currently accepted model. New experimental evidence on the gasification process of ammonium perchlorate burning under a very wide variety of conditions shows that the dissociation is generally better represented by a kinetic decomposition law (with an activation energy of about 30 kcal/mole) then by an equilibrium law. During combustion, some exothermic redox reaction in the condensed phase probably accompanies dissociation of the salt. At low pressures, the burning rates of composite mixtures of ammonium perchlorate with organic fuels are little affected by fuel-binder properties, other than heat of combustion, but at high pressures the converse is true. Possible reasons for this have been explored experimentally. At constant final-flame temperature, the volumetric loading of a binder appears to be more important than its thermal stability, and the idea of a fuel “barrier” hindering propagation of the ammonium perchlorate monopropellant flame at high pressures is supported. Rates of flame travel along ammonium perchlorate binder interfaces are not very different from the burning rates of the corresponding composite propellant, and does not now seem to be a rate-controlling feature.