Low Pressure Burning of Ammonium Perchlorate Composite Propellants

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Abstract
The combustion wave structure of ammonium perchlorate (AP) composite propellants was observed by microphotographs and the heat transfer process from the gas phase to the con-densed phase was determined by microthermocouples. Since the thickness of the combustion wave increased with decreasing pressure, the experiments were conducted at low pressures below I atm in order to examine the structure as detailed as possible. It has been determined that the reaction zone in the gas phase consists of heterogeneous flamelets produced by the decomposed AP monopropellant flames and the decomposed gases of polymeric fuel binder. The thickness of the reaction zone decreases with decreasing the concentration of binder at a constant pressure. The heat feedback from the gas phase to the condensed phase and the heat release at the burning surface are very dependent on the type of binder used. The reaction rate in the gas phase is greater and the heat release at the burning surface is smaller for the binder (HTPE) which contains higher oxygen concentration in its structure when compared with the binder (HTPB) which contains lower oxygen concentration in its structure.