Emission Characteristics of Passively Fed Electrospray Microthrusters with Propellant Reservoirs

The characterization of a miniaturized ionic liquid electrospray thruster for nanosatellite applications is presented. The thruster investigated features an emitter array of 480 emitter tips per square centimeter and a 1 cm3 propellant tank with an entirely passive propellant supply; it is operated at a power level of less than 0.15 W. The paper presents energy- and mass-resolving beam spectroscopy of the packaged thruster system, as well as two independent thrust measurements. This allows derivation of thruster performance parameters under realistic firing conditions, including individual thruster efficiency contributions, specific impulse, and thrust. The total thruster efficiencies of 36%; specific impulse of ∼760 s, including all losses; and thrust of 11–12.5 μN are presented at emission currents of 150 μA for a device of ∼1 cm2. The current emission data without current decay of ∼90 h are presented with a maximum of 172 h.