Electrospray of an Energetic Ionic Liquid Monopropellant for Multi-Mode Micropropulsion Applications

The multi-mode chemical-electric propulsion capable energetic ionic liquid propellant [Emim][EtSO4]-HAN is electrosprayed in a 100 μm capillary emitter to test the electricmode performance of the propellant. The ionic liquid exhibits stable electrospray emission in both cation and anion extraction modes at a nominal extraction voltage of 3400 V. Near field measurements of current and mass flow rate distribution are taken at flow rates from 0.19 nL/s to 3.06 nL/s. Total emission current, as measured by Faraday cup and integrated, increases from 754 nA to 3195 nA for cation emission and from 552 nA to 2012 nA for anion emission. The thrust and specific impulse at 0.19 nL/s flow rate is 1.08 μN and 412 seconds, respectively, with a beam power of 2.22 mW. At 3.06 nL/s, the thrust is 8.71 μN and the specific impulse is 204 seconds with a beam power of 8.85 mW. Extrapolation of the current data shows that specific impulse in excess of 1000 seconds is achievable through optimized feed system and emitter design.