Enhancing the Regression Rate of Hydroxyl-Terminated-Polybutadiene-Based Mixed Hybrid Rockets

This study has identified potential hydroxyl-terminated-polybutadiene (HTPB) based fuel compositions that provide a high-density specific impulse but do not burn like a solid propellant. Due to low solid loading in these fuel compositions, precuring the HTPB and isophorone diisocyanate mixture is necessary to get uniform density and composition across the length of the grain. Nearly 7 h of precuring gave the best results in terms of uniformity of the propellant composition. This study also discusses the effect of available burn rate modifiers for ammonium perchlorate and a type of aluminium on the enhancement of regression rate in mixed hybrid rockets. Finally, the hybrid propellants developed had an oxidizer mass flux index close to 0.5, which is desirable.