Experimental progress towards the MicroThrust MEMS electrospray electric propulsion system

This paper describes the experimental progress towards an operational microfabricated electrospray thruster, as part of the EU FP7 “MicroThrust” Project. Microfabrication of an electrospray multiplexed thruster allows the seamless manufacturing of arrays of emitters, combining high specific impulse with sizeable thrust. The resulting thruster can thus be extremely efficient with a thrust approaching ≈100µN, depending on array size. We are working within the European FP7 project MicroThrust consortium to develop the complete MEMS electrospray array thruster for 10-100 kg class satellites to enable these small spacecraft to perform large delta-V missions (5 km/s). This includes the manufacture of MEMS Silicon electrospray emitters, and also a passive propellant feeding system, a miniaturized high voltage power supply, and the investigation of possible missions. We report here on the experimental testing of the micromachined Silicon capillary arrays, constituting arrays of either 91 or 127 emitters. A detailed description of the manufacture of the arrays will be described in a separate companion paper. To increase the specific impulse and thrust, and to reduce the plume angle, an accelerator has been integrated into the thruster Silicon chips. The thrust, and specific impulse has been measured using a Time-of- Flight (ToF) system, whilst the emitter current has been measured as the applied voltage was varied. The plume angle has been discerned using a translating Faraday cup.