Design and Experimental Validation of a Gallium Field Emission Electric Propulsion Thruster

Field Emission Electric Propulsion (FEEP) thrusters use a liquid metal ion source (LMIS) to generate thrust. They are desirable due to their compact and simple architecture and instantaneous sub-μN-scale throttling capabilities. Gallium is advantageous over many common propellants such as indium and cesium due to its combination of low melting temperature (85.6 °F), limited reactivity, and low toxicity. Presented is the design, manufacturing, and validation of a low-cost, gallium-fueled, slit-type FEEP thruster. Measurements of plume current distribution, plume energy spectra, thruster mass flow, and emitter/extractor voltage and current were conducted alongside visible spectrum imaging. This allowed for accurate characterization of the thrust, specific impulse, and thrust efficiency of the Gallium FEEP Thruster (GFT). This study indicates that compact FEEP architectures can be fabricated using 3-axis machining and can be used effectively with gallium as a propellant, leading to lower operation temperatures than indium FEEP thrusters and higher system safety than cesium FEEP thrusters. The thruster was experimentally measured to produce 100 ± 40 μN of thrust, with a specific impulse of 10,000 ± 4,000 seconds and a power draw, including heating, of 14 ± 2 W.