Ignition evaluation of monopropellant blends of HAN and imidazole-based ionic liquid fuels

Potential dual-mode monopropellant/electrospray capable binary mixtures of hydroxyl ammonium nitrate with ionic liquid fuels [Bmim][NO₃] and [Emim][EtSO₄] are synthesized and tested for monopropellant ignition capability in a micro reactor setup. The setup is benchmarked using 30% hydrogen peroxide solution decomposed via silver catalyst. Results show similar trends, but variance in the quantitative data obtained in literature. A parametric study on the geometry of the sample holder that contains the catalyst material in the reactor shows a large variance leading to the conclusion that quantitative data may only be compared to the exact same geometry. Hydrazine decomposition was conducted on unsupported iridium catalyst. The same trends in terms of pressure rise rate during decomposition (∼160 mbar/s) are obtained with unsupported catalyst, but at 100°C instead of room temperature for tests conducted on supported catalysts in literature. Two catalyst materials were tested with the novel propellants: rhenium and iridium. For the [Bmim][NO₃]/HAN propellant, rhenium preheated to 160°C yielded a pressure slope of 26 mbar/s, compared to 14 mbar/s for iridium and 12 mbar/s for no catalyst at the same temperature. [Emim][EtSO₄]/HAN propellant shows slightly less activity at 160°C preheat temperature, yielding a pressure slope of 20 mbar/s, 4 mbar/s, and 2.5 mbar/s for injection onto rhenium, iridium, and the thermal plate, respectively. Final results indicate that desirable ignition performance may potentially be obtained by using a supported rhenium catalyst, since the pressure slopes obtained with the new propellants on unsupported catalyst lie between that of hydrazine on iridium at 50°C and room temperature.