| Hybrid rocket fuels typically exhibit lower regression rates than comparable solid rocket motors, though benefits in safety and operability are evident. Lower rates necessitate large internal grain ports and poor volumetric loading of the fuel. Three formulations of a mixed oxidizer hybrid propellant were evaluated with gaseous oxygen to determine performance improvements over pure hydroxyl-terminated poly-butadiene hybrids using a 12 inch long, 1.5 inch diameter center-perforated motor. Experimental grain formulations included ammonium perchlorate (oxidizer) and iron oxide (catalyst) at levels set by application of a quadratic mixture study. Results suggest that improvements in regression rate up to are possible compared to pure hydroxyl-terminated poly-butadiene when a level of 27.5% oxidizer and 2.5% catalyst are employed. Start/stop capability was maintained with all formulations tested, though smoking was observed under some conditions. Combustion instabilities were noted during operations at high chamber pressures and are likely due to grain chuffing. |
