Combustion-mode transition of a solid propellant rocket motor by nitrogen gas injection and combustion gas release

Abstract

Some ammonium perchlorate composite propellants have an intermediate self-quenching pressure range around several MPa. When the propellant burns in a motor with an appropriate throat area, the motor changes its chamber pressure in dual combustion modes. The objective of this study is to make cyclic combustion-mode transitions and to achieve the thrust magnitude control of solid rocket motor. The transitions from the low mode to the high mode were attained by nitrogen gas injection, and those from the high mode to the low mode were done by a brief gas release with appropriate nitrogen gas injection. Without the gas injection, the transition from high mode to low mode was not accomplished and the combustion was interrupted. The timing to shut down the combustion gas release was important as well as the timing to inject the nitrogen gas. The valve timing was controlled according to the chamber pressure. Three-time cyclic combustion-mode transitions were accomplished.