Ionic Liquid Dual-Mode Spacecraft Propulsion Assessment

Abstract

Analytical and numerical investigations of the performance of a series of potential dual-mode propulsion systems using ionic liquids are presented. A comparison of the predicted specific impulse of ionic liquids with hydrazine and unsymmetrical dimethylhydrazine shows that ionic liquid fuels have a 3–12% lower specific impulse when paired with a nitrogen tetroxide oxidizer. However, when paired with hydroxylammonium nitrate oxidizer, the specific impulse of the ionic liquids is 1–4% lower than that of hydrazine and unsymmetrical dimethylhydrazine paired with nitrogen tetroxide. Analytical investigation of an electrospray electric propulsion system shows that ion extraction in the pure ion regime provides a very high specific impulse, outside the optimum range for potential missions. Results suggest a deceleration grid, a lower ion fraction, or emission of higher solvated states is required. Analysis of a dualmode ionic-liquid-propelled spacecraft shows that the electric propulsion component determines the overall feasibility comparedwith current technology. Results indicate that the specific power for an ionic liquid electrospray systemmust be at least 15 W=kg in order for a dual-mode ionic liquid system to compete with traditional hydrazine and Hall thruster technology.