Hybrid Rockets as Post-Boost Stages and Kick Motors

Hybrid rockets are attractive as post-boost stages and kick motors due to their inherent safety and low cost, but it is not clear from previous research which oxidizer is most suitable for maximizing Delta V within a fixed envelope size, or what impact O/F shift and nozzle erosion will have on Delta V. A standard hybrid rocket design is proposed and used to clarify the impact of component masses on Delta V within three 1 m(3) envelopes of varying height-to-base ratios. Theoretical maximum Delta V are evaluated first, assuming constant O/F and no nozzle erosion. Of the four common liquid oxidizers: H2O2 85 wt%, N2O, N2O4, and LOX, H2O2 85 wt% is shown to result in the highest Delta V, and N2O is shown to result in the highest density Delta V, which is the Delta V normalized for motor density. When O/F shift is considered, the Delta V decreases by 9% for the N2O motor and 12% for the H2O2 85 wt% motor. When nozzle erosion is also considered, the Delta V decreases by another 7% for the H2O2 85 wt% motor and 4% for the N2O motor. Even with O/F shift and nozzle erosion, the H2O2 85 wt% motor can accelerate itself (916 kg) upwards of 4000 m/s, and the N2O motor (456 kg) 3550 m/s