Electrospray Thruster Plume Dynamics: Insights from Precise PP Coulomb Field Simulation

Abstract: Electrospray thrusters are one important type of micropropulsion systems being developed for next-generation space missions, yet the primary challenge to their operational lifespan is propellant overspray resulting from wide plume angles driven by Coulomb interactions among charged droplets. While existing models often employ truncated Coulomb field approximations, such simplifications compromise accuracy in predicting divergence dynamics. In this study, a particle-particle (PP) simulation method is used to directly calculate the interactions between droplets in an electrospray plume coupled with background electric field effects for simulation. The model integrates Boris pusher for numerical integration, validated through binary collision tests verification. Parametric analysis systematically evaluates six key variables, droplet charge, droplet mass, emission interval, droplet initial velocity, and electric field components, to quantify their impacts on plume divergence. The shape of the simulated electrospray plume and the velocity of the droplets in it are analyzed. Parametric analysis demonstrate that reducing droplet charge, increasing droplet mass, extending emission time intervals, and elevating initial drift velocity collectively reduce plume half-angle. These results quantitatively establish parameter plume relationships, providing direct guidance for thruster optimization.