Ionic liquid electrospray thrusters are capable of producing micronewton precision thrust with high thrust-power ratio but have yet to demonstrate lifetimes that are suitable for most missions. Accumulation of propellant on the extractor and accelerator grids is the most significant life-limiting mechanism. In this study, we develop a life model to examine the effects of design features, operating conditions, and emission properties on the porous accelerator grid saturation time of a thruster operating in droplet emission mode. Characterizing a range of geometries and operating conditions reveals that modifying grid aperture radius and grid spacing can significantly improve thruster lifetime. Misalignment and tolerance analysis shows the potential for up to 50% lifetime reduction. In addition, examining the impact of electron backstreaming shows that increasing aperture radius produces a signifìcant increase in backstreaming current compared to changing grid spacing. A study of accelerator grid bias voltages reveals that applying reasonably strong accelerator grid potential can minimize backstreaming current to negligible amounts for a range of geometries.
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