3D NUMERICAL SIMULATION OF THE FEEP THRUSTER PLUME

A three-dimensional numerical model of the linear slit FEEP thruster was recently developed at Alta. The code is based on a Particle-In-Cell simulation technique, with solution of the Poisson’s equation achieved by a hybrid method resulting from the joining of the Boundary Element Method and the iterative Multigrid method, so that the simulation can be extended to regions very close to the electrode surfaces. Motion of the particles is simulated both in the inter-electrode region and in the post-accelerator, downstream region, with seamless transition between the different domains. The code also allows simulation of the simultaneous firing of multiple thrusters with overlapping plumes, including the effects of electrostatic and collisional interactions between the ion beams. Additional computational modules have been implemented to address the phenomena related to the formation of charge-exchan ge (CEX) ions. Frequency and density distribution of CEX ions in the plume is computed using a Direct Monte Carlo Simulation method. The probability of CEX ions collision with the spacecraft walls is computed and the collision energy is evaluated using direct simulation of the impingement events. In the paper, the computational model architecture is illustrated and the results of several simulation runs in different thruster operating conditions are presented. A simple case of combined thruster / spacecraft simulation is shown, addressing the CEX backflow effects on the impinged surfaces.