Studies on Thrust Density in Ionic Liquid Electrospray Thrusters
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corrado-mcorrado-phd-aeroastro-2026-thesis.pdf
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Author(s)
Corrado, Matthew Nicholas
Advisor(s)
Lozano, Paulo C.
Date Issued
May 2026
Publisher
Massachusetts Institute of Technology
Abstract
Electrospray thrusters are a type of in-space propulsion technology operating on the principle of electrostatic acceleration of ions. Alluring for long-duration missions or low-thrust maneuvers due to their ability to achieve high specific impulse relative to chemical thrusters, electrosprays also feature several benefits over alternative forms of high-specific-impulse electric propulsion (EP). However, one key drawback to electrospray thrusters, their relatively low areal thrust density, has prevented their widespread adoption and utilization outside of academic settings. Widely accepted theoretical limits for thrust density in electrospray propulsion are much greater than the levels that have been achieved in practice, so many attempts at increasing thrust density through design have been undertaken in recent years. Despite these attempts, meaningful forward progress in electrospray thrust density has shown to be elusive, hinting at the existence of factors affecting thrust density that have been improperly neglected in the estimation of theoretical limits. Here, we seek to identify and characterize those factors to encourage more thoughtful consideration of the effects that influence electrospray thruster performance and foster smarter strategies for improving upon the state of the art.
This work begins with a computational investigation of the flow through and emanating from an array of porous electrospray emitter tips. The internal flow is governed by fluid dynamics through porous media. We develop a numerical model for computing the flow rate of ionic liquids through a porous electrospray emitter that depends on geometries and material properties. We subsequently define scaling relationships for changes in those geometric and material properties with changes in density, allowing us to computationally expand and contract the density of a notional thruster for the purpose of evaluating trends in the fluid dynamics with changes in density. The external flow is governed by electrodynamics of ion beams. A kinetic plume simulation based on the particle-in-cell (PIC) method is built to study the dynamics of electrospray plumes, especially as density is scaled. Much like in the case of the porous flow models, the strategy of numerical simulation enables investigation of extremely high-density devices, illuminating the effects that increasing density has on plume dynamics. Both the porous flow and plume kinetics models yield similar findings, though for fundamentally different reasons. Namely, we find that the previously-accepted scaling rule for thrust density in electrospray thrusters is a poor approximation. Both of the factors studied here have significant limiting effects on thrust at elevated density levels, underscoring that there are several important factors that must be carefully considered in the pursuit of high-density electrospray propulsion.
This work concludes with an experimental study of thrust density in electrospray propulsion, including the development of a family of small-pore electrospray emitters suitable for fabrication into high-density arrays. Versions of these thrusters are tested at varying levels of density, a range including the current state of the art and expanding into high-density levels previously unexplored experimentally. We find that at current (450 µm pitch) and moderately elevated (225 µm pitch) densities, limiting factors do not yet have significant effects and the previously accepted scaling rule approximates both the experimental results and the numerical models well. In doing so, we showed test results from a porous, pure-ion electrospray thruster with record-breaking density. Still yet to be seen are experimental studies at significantly elevated density levels at which the emergence of limiting effects are predicted by the models, an area that we recommend for continued future study.
MIT Department
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
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