Computational modeling of electric discharge inside electric propulsion systems by a hybrid PIC-MCC/FVM approach

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Goal of the present research project is the development of a new modeling concept for plasma flows and its use for the numerical study of an arcjet thruster. This type of electric propulsion system for spacecraft enables the generation of a small and precise thrust which is in turn of vital importance for the attitude control of miniaturised satellites and for the envisioned formation flight of future satellites. The knowledge gained from the project will improve the understanding of complex plasma phenomena, such as the experimentally observed increase of electron mobility in Hall thrusters.One of the main disadvantages of the continuum-based modeling of plasma phenomena in electric propulsion systems is the necessary estimation of several physical quantities such as electric conductivity, anode temperature and transport coefficients. This estimation is often based on empiric approaches, which mainly results from the high complexity of plasma phenomena. Furthermore, full kinetic approaches, which generally avoid the estimation of transport coefficients, often exhibit prohibitively high computational requirements. In the present research project, an approach based on a hybrid model with manageable computational requirements will be pursued. To this end, charge carriers are modeled with a kinetic (PIC) approach and the neutral gas in the plasma is handled as a fluid. The results of the fluid equations are used to produce a cloud of neutral particles, which interact with the kinetic modeled electrons. Ionization and recombination rates are determined based on the kinetically obtained results and are incorporated as source terms in the fluid equations for the neutral gas. Some of the challenges regarding the description and numerical modeling of plasma phenomena in electric propulsion systems are the determination of the electric conductivity in the nozzle of an arcjet thruster without using empirical models.a nd the development of computationally efficient approaches for technical applications in which large differences of time and length scales of the physical processes exist.The main goal of the present research project is the investigation of a numerical, hybrid model that allows the accurate description of the plasma phenomena inside an electric propulsion system. In the first phase of the project, the model will be developed and validated focused on the ionization and plasma behavior inside arc jet thrusters. After conclusion of the project, a PIC-MCC/FVM-Model is available. The developed model is based on a kinetic description of electrons and enables the determination of important plasma and ionization parameters at a kinetic level.