Synergistic effect of a hybrid additive for hydrogen peroxide-based low toxicity hypergolic propellants

Abstract Hypergolic bipropellants based on high-test peroxide (HTP, >85% H2O2) have traditionally emerged as low-toxicity propellants for space applications. However, the late-ignition performance of HTP-based fuel restricts its potential use in particular applications, such as high-precision auxiliary response thrusters. In this study, the synergistic effects of new hybrid additives (reactive additive: catalytic additive), NaBH4:NaI, and NaBH4:NH4I were, for the first time, demonstrated to improve the ignition performance of low-toxicity fuels with 95 wt.% H2O2. The effect of changes in the weight percentage ratios of the reactive and catalytic additives on the ignition performance was investigated. The fuels without additives were non-hypergolic with 95 wt.% H2O2. However, at specific concentrations, the hybrid additives in fuels markedly lowered the ignition delay time (IDT) to less than 3 ms. Notably, ethylenediamine containing 10 wt.% hybrid additives of NaBH4:NaI and NaBH4:NH4I at a specific additive weight ratio (6.5:3.5) yielded an average IDT of 2.75 and 2.69 ms, respectively. Thermal analysis revealed that the hybrid additive improved the thermal stability of the fuels. The theoretical vacuum-specific impulse of these fuels was calculated using the NASA-CEA code. The results of this study confirm the validity of our approach for developing relatively low-toxicity hypergolic fuels for space propulsion.