Combustion characteristics of HAN-based liquid propellant

A new composition of Hydroxyl Ammonium Nitrate (HAN) based solution containing Ammonium Nitrate (AN), Methanol, and Water (H2O) was developed for a monopropellant of reaction control system (RCS) as an alternative to conventional Hydrazine. Burning rate of the solution is moderate at operating pressures of RCS thruster. Comparing this solution with hydrazine, Isp is 20%higher, the density is 1.4 times, the freezing point is much lower, and the toxicity is low, which make this solution promising for RCS propellant. Combustion mechanism of this solution was investigated. Burning behavior was observed using a medium speed camera, and temperature profile of combustion wave was measured with a fine φ2.5 microns thermocouple. From these results, the instability of liquid interface may trigger jumping of burning rate to violently high region, and methanol was found to be effective to reduce the bubble growth rate in the solution.