Analysis of Teflon Pulsed Plasma Thrusters using a modified slug parallel plate model

The Pulsed Plasma Thruster (PPT) is a reliable, relatively simple and low cost electric propulsion thruster that has been used widely in space flight mission. Numerical simulation is an important part of the overall research and development process for PPTs. To provide physical insights and guidance toward design of consistently efficient PPTs, a modified slug model for parallel-plate PPTs is presented in this paper. This new model is formed on the basis of electromechanical model (i.e. slug model), which has been published by American Worchester Polytechnic Institute. Different from common slug model, this new model assumes that after the plasma slug is formed there is additional mass accumulated to the plasma as it accelerates down the discharge chamber and force within the PPT comes from an gas dynamics due to build up of pressure within the thruster chamber and a magnetic acceleration from the Lorentz force. So the modified slug model can calculate the ablated mass per discharge and can describe the electromagnetic acceleration and aerodynamic efficiency in the process of plasma flow. The late time ablation (LTA) is sublimation of propellant that takes place after the main discharge, due to the propellant, temperature being above its sublimation point, and LTA is considered as one of the main contributors for PPT's low efficiency. Thus the new model also analyze the impact of LTA for the performance of PPT according to the velocity of decomposed mixture of neutral atoms, monomers and free-radical chains of molecules ("slurry") after the main discharge. Finally, influences of variations of electric parameters and configuration parameters on thruster performance are studied by numerical simulation.