Flexible Three-Dimensional Modeling of Electric Thrusters in Vacuum Chambers.

摘要

A national team of researchers is developing a software system, COLISEUM, which performs calculations of plasma propagation and interaction with arbitrary 3D surfaces. The applications of COLISEUM are wide-ranging, hut include simulating engine test configurations inside vacuum chambers and predicting sputtering and re-deposition on spacecraft surfaces. COLISEUM allows users to easily define complicated 3-D geometries using off the shelf CAD software, then select from a set of plasma expansion models of varying fidelities and numerical complexity to perform the solution. Once the object surfaces are created, the user can run different types of simulations for the same geometry. With this system, low fidelity models can he used to verify the geometry and boundary conditions, and to obtain first-order predictions. Higher fidelity models are then used to obtain more accurate predictions with greater cost in computation time. This paper describes the simulation of a Hall thruster firing inside a vacuum chamber, and the execution of two types of simulations for the same geometry: one in which the equilibrium sputter and deposition rates are calculated, and another in which the Hall thruster plume expansion is calculated. The sputter and deposition calculations are made with an iterative ray tracing algorithm which takes into account re-sputtering of deposited material. The plume expansion calculations are performed with a particle-in-cell (PIC) algorithm which includes wall collisions and wall recombination. Techniques are incorporated that decrease the computation time required for the PIC simulation to relax to steady state.