Emission Measurements and in-situ Observation of Ionic Liquid Electrospray Thrusters with Longitudinally Grooved Emitters

Abstract

An externally wetted emitter array with longitudinally grooved structures for ionic liquid electrospray thrusters has been fabricated to improve the ionic liquid transport to the emitter tips. Two grooved emitter shapes with different groove depths were successfully fabricated using micro-electro-mechanical systems process techniques. We evaluated the current-voltage characteristics and conducted in-situ observation with a high-speed microscope. The experimental results of the ion emission have shown that the absolute emission current increases compared with our previous emitter without grooves. This tendency becomes stronger with deeper grooves. In addition, the slope of the current-voltage curve for grooved emitters does not decrease even when high voltages are applied, indicating that the grooved structure improves the ionic liquid transport to the emitter tips. However, it was found that deeper grooving also increased the percentage of the current intercepted by the extractor electrode. The high-speed microscope observation has shown that too much ionic liquid deposited on the extractor causes the ion emission from the extractor to the emitter, known as backspray, and implied that no large droplets are emitted for both grooved emitter structures.