Microfabricated Electrospray Thruster Array with High Hydraulic Resistance Channels

Electrospray thrusters can deliver the efficient primary propulsion and attitude control actuation needed by small satellites. The microfabricated multiemitter array is an ideal implementation of this technology because it addresses the thrust, volume, mass, and scalability requirements across the size range of small satellites. This paper describes the microfabrication and testing of an internally fed 64-emitter array. The main goal is to decouple the design and fabrication of the emitters from the need to provide a flowpath with sufficient hydraulic resistance for each emitter. The latter has traditionally been achieved by reducing the diameter of the emitter’s inner channel or by filling it with a bed of beads; whereas in this paper, individual flow-restrictive channels are etched on the back of the emitter wafer, connecting each emitter to a common distribution manifold. The source operates steadily in vacuum. Beam interception by the extractor is negligible in a wide range of flow rates and emitter potentials. The thrust, mass flow rate, specific impulse, and propulsive efficiency are calculated using the time-of-flight technique. These parameters range between 8.1 and 54.0 μN, 3.5×10−9 and 5.73×10−8 kg/s, 96 and 236 s, and 61 and 75% using the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as propellant.