Plasma ignition and combustion of JA2 propellant

Experiments were performed to investigate the effects of various parameters on plasma-driven ignition and combustion of a double-base propellant under closed-chamber conditions. The parameters varied include input electrical energy, nozzle length and inner diameter, nozzle exit to propellant distance, as well as propellant sample thickness. Chamber pressure was measured to determine the ignition delay and to deduce the regression rate. High-speed images of the plasma jets and combustion event were also recorded. At low plasma energies, rapid, plasma-driven burning occurred, but self-sustained burning was not achieved. With moderate plasma energies, combustion of the propellant exhibited a two-stage burning behavior: one stage of plasma-driven rapid burning that occurred during the plasma pulse and a second stage of slower self-sustained burning that occurred with a clear delay after the first stage. When plasma energy was increased further, the two-stage behavior became less distinct and eventually disappeared, leaving only one stage of burning. Nozzle length and diameter affected the ignition and combustion characteristics as a result of energy losses from the plasma as it flows through the nozzle. The propellant burning behavior is also affected by both nozzle-sample distance and sample thickness. High-speed images revealed vigorous motion of gases in the closed chamber, which was induced by the plasma jet. Also, the images showed what appeared to be JA2 fragments; this observation was confirmed by recovery of fragmented propellant after some of the tests.