Study on the modes transformation and emission characteristics of Ionic Liquid Electrospray Thrusters

Abstract

Ionic Liquid Electrospray Thrusters (ILETs) exhibit distinct emission characteristics when operating in different emission mode under different conditions, which can significantly impact their performance. Therefore, to optimize the performance of ILETs and make them suitable for a wide range of space missions, it is necessary to investigate the emission mode characteristics of ILETs. In this study, the ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-Im) was used to conduct experiments at varying supply voltage and flow rate conditions. The emitted current was measured and the liquid surface was imaged using a high-speed camera. The emission mode was estimated using algebraic calculations. Experimental results revealed that ILETs operate in the Ion-droplet Mixed mode at low flow rates, while the emission mode transforms into the Droplet mode as the flow rate increases. Similarly, as the supply voltage increases, the emission mode transforms from the Droplet mode to the Ion-droplet Mixed mode. The liquid surface height decreased with the supply voltage increase in each mode, and it increased with the flow rate in the Droplet mode. Notably, the liquid surface height in the Ion-droplet Mixed mode was similar to that in the Droplet mode at the lowest flow rate. Furthermore, the ion ratio significantly affected the thrust and specific impulse of ILETs.