Hot fragment conductive ignition of nitramine-based propellants

Hot fragments generated during the impact of shaped-charge jets may penetrate the cartridge casing and induce propellant ignition. The major objective of this study is to acquire a better understanding of hot fragment conductive ignition behavior of nitramine-based XM39 and M43 propellants. The confinement effect of the cartridge is simulated by an enclosure within which the pyrolysis products can accumulate and significantly increase pressure. Both theory and experiments showed that the ignition threshold was a strong function of confinement. At low pressures, the XM39 propellant was more susceptible to ignition, because its binder decomposition is more exothermic than that of the M43 propellant. At highly confined conditions, which allow for chamber pressurization, the M43 ignition threshold became lower than that of XM39 propellant. The reduction of the ignition threshold is caused mainly by exothermic reactions between CH2O and NO2 species, which are enhanced under gas accumulation conditions.