HYBRID MOTOR CONCEPTS (II)-DEVELOPMENT OF A TANDEM SOLID-HYBRID MOTOR FOR ZONING DEMONSTRATION,

A single-chamber rocket motor containing both a hybrid fuel grain and a solid propellant charge has been developed to demonstrate that termination of the hybrid motor can provide accurate missile zoning. The hybrid fuel charge was in tandem with and forward of the solid propellant charge which provided the minimum impulse of the unit and a minimum missile range. The volume vacated by the solid charge served as a mixing chamber for more efficient hybrid combustion. A baffle plate separated the two grains and provided additional mixing. The solid propellant charge burned for 2.2 seconds providing a total impulse of 1100 lbf-sec the maximum operating time of the unit was 9 seconds with 4000 lbf-sec of total impulse. The average pressure was 700 psia and thrust was 500 lbf. Using IRFNA and an inert aluminized binder as hybrid propellants, specific impulses of 235 lbf-seclbm were delivered, which was approximately 93 of the theoretical equilibrium specific impulse. A piston expulsion system for the oxidizer was built and tested with the hybrid motor in a series of firings to determine reproducibility. Standard deviation of total impulse for eight firings was 0.9. Development of the motor is complete and flight tests are awaiting completion of a flight test vehicle. Author