Initiation of Deflagration Waves at Surfaces of Ammonium Perchlorate—Copper Chromite—Carbon Pellets

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Abstract
A study was made of the initiation of a deflagration wave at the surface of ammonium perchlorate—copper chromite—carbon pellets in nitrogen at 25 atm. The relationship between energy flux density I and exposure time τI, describing the boundary conditions necessary for initiation, was measured. Integration of the governing partial differential equation using experimentally determined chemical and physical parameters and the boundary conditions gave the temperature T(0, τI) of the initiating surface at the moment τI of cutoff of the energy pulse, and a lower bound for the minimum thermal ignition time τim. T(0, τI) for ammonium perchlorate with 5% copper chromite was 380±31°C. It was drastically lowered when carbon was added, the amount of lowering being proportional to carbon concentration. It ranged from 300° to 215°C for carbon percentages ranging from 0.5 to 4. For given composition T(0, τI) was independent of flux density over the range 9 to 63 cal/cm2·sec. Initiation occurred substantially before the calculated minimum thermal ignition time τim. The results provide support for the view that thermal ignition of the solid material is not a prerequisite for initiation of a deflagration wave.

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