Fabrication and Characterization of Porous Metal Emitters for Electrospray Thrusters

A repeatable method based on conventional micro fabrication techniques for creating sharpened emitters from porous tungsten has been explored. A laboratory demonstration thruster comprised of 49 of these porous tungsten emitters has been built and tested. The demonstration device operates on the electrostatic field evaporation of ions from ionic liquids. The emitters are contained in three linear emitter arrays which have been shown to support an increase in current of over an order of magnitude when compared to solid cylindrical emitters. Time-of-flight mass spectrometry has be used to show that the emitted beam is purely ionic and is comprised of two species of ions in both positive and negative modes of operation. In addition, thrust measurements conducted on a torsional balance show that the demonstration device is capable of thrusts as high as 5.6 μN at a current of 48 μA and a voltage of 2437 volts for a specific impulse of above 3500 s.