Hybrid modeling of ionic emission and plume dynamics in electrospray thrusters

Electrospray thrusters, a rapidly evolving class of electric propulsion devices, hold significant potential for enhancing the efficiency and feasibility of miniaturized spacecraft. These thrusters operate by applying an electrostatic field to a liquid ion source, from which ions are extracted and accelerated, thereby generating thrust. This study presents a novel multiscale framework to model an electrospray source undergoing pure ionic emission. The model consists of a semi-empirical emission model, informed by electrohydrodynamic meniscus simulations, that is weakly coupled to a particle-in-cell/direct-simulation Monte Carlo based plume model that captures field-free fragmentation. Simulations are configured to match the geometry and operating conditions of the Air Force Electrospray Thruster Series 2 (AFET-2) developed at the Air Force Research Laboratory and are compared against measurements of emission current and thrust. Spatial characteristics of the plume, including beam intensity and current density distributions, are parameterized using a super-Gaussian profile, and their evolution with respect to extraction voltage is investigated.