Ion Dynamics in Porous Emitter Ionic Liquid Electrospray Thrusters

Abstract

We report on the effect of feeding the propellant on the ion beam in porous ionic liquid electrospray thrusters and discuss it in the context of the ion dynamics in the ionic liquid. Ionic liquid electrospray thrusters are a promising, game-changing electric propulsion system that enables high ∆V even for small spacecraft. Especially, a porous emitter is beneficial for storing ionic liquids and is widely used in the development of electrospray thrusters. However, there are no guidelines for the design of propellant feeding in porous emitters. This is one of the bottlenecks in improving the thruster technology. To understand the effect of the pressure of the feeding, we applied feeding pressure to the emitter using a liquid column, using gravity to make it an actively fed system. This active feeding with positive pressure enhanced the emitted current. Based on the theoretical model in [Takagi et al., J. Appl. Phys, 135 (2024), 244502], applying feeding pressure increased the ion transport driven by the ion pressure gradient, resulting in an increase in the emitted current. The importance of controlling the feeding pressure for the porous emitter is thus clarified.