Emission and performance characterization of ionic liquids for an externally wetted electrospray thruster
David Villegas-Prados, Javier Cruz, Mick Wijnen, P. Fajardo, Jaume Navarro-Cavallé
Abstract
Ionic liquids are the base for electrospray propulsion, yet few have been explored. The performance of an externally wetted electrospray thruster is characterized for seven different ionic liquids: 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), dicyanamide (EMI-DCA), bistrifluoromethylsulfonylimide (EMI-Im), thiocyanate (EMI-SCN), ethylsulphate (EMI-EtOSO3), triflate (EMI-OTf), and trifluoromethanesulfonate (EMI-TFA). This research marks the first time that the latter four liquids are reported for externally wetted emitters. A complete thruster assembly has been tested with each of the propellants. Using time-of-flight mass spectrometry and a Faraday cup for beam divergence, the performance of these ionic liquids has been characterized, assessing thrust, specific impulse and thrust efficiency. EMI-BF4, EMI-DCA and EMI-SCN operated in pure ionic regime while EMI-Im, EMI-EtOSO3, EMI-OTf and EMI-TFA operated in mixed regime.