Multiscale Modeling of Hall Thrusters

Multiscale Modeling of Hall Thrusters Hall thrusters are efficient space propulsion devices that produce thrust by accelerating quasineutral plasma. The thruster consists of a channel with one end open to the ambient environment. The neutral propellant is injected at the closed end and is ionized by electrons produced by an externally mounted cathode. A radial magnetic field is applied across the channel to restrict the electron flow and increase the ionization efficiency. The magnetic field also become lines of constant potential and induce an electric field that accelerates the ions out of the device. This thesis introduces a novel approach for modeling these devices. Hall thrusters have been operated in space for over 40 years, yet no code yet exists that can selfconsistently predict their operation and lifetime. This shortcoming is to a large extent driven by the presence of significantly different spatial scales that dominate the internal plasma dynamics. One such a scale is the microscopic scale of an electron orbiting about a magnetic field line. This scale determines the rate with which electrons diffuse across the field line which becomes an important parameter in modeling the internal thruster discharge. It is not numerically feasible to include electron motion when dimensions of a thruster are considered. As such, Hall thruster codes typically utilize a hybrid approach in which electrons are modeled as a fluid with electron transport given by an analytical expression. These expressions do not correctly capture the experimentally-observed behavior. In this work, a kinetic code was developed to de-