Temperature-Dependent Performance of Electrospray Thrusters with ASCENT Monopropellant

Abstract

In this work, we investigate the emission characteristics and performance of a passivelyfed electrospray thruster with ASCENT (AF-M315E) monopropellant at temperatures from 20C to 60C. The current-voltage characteristics, energy spectra, beam divergence, and mass spectra of the thruster are quantified in both the positive and negative emission modes. Results show that the startup voltage of the thruster decreases as temperature increases. The average specific charge of the ion plume also decreases, more dramatically in the positive mode than the negative mode, but is offset by a decrease in energy efficiency. When incorporating these losses, we find a relatively constant thrust with increased temperature (around 6-7 uN at 100uA and 10-12 uN at 150uA) which is surprising given previous work with conventional ionic liquids. Specific impulse is found to decrease with temperature, from roughly 680 s at 20C to 580 s at 60C. Thrust-to-power is found to increase slightly with temperature due to a decrease in required power.