Recent Advances in Hall Thruster Scaling Methodology

The past two decades have seen an increasing role of Hall thrusters in space propulsion thanks to their favorable performance characteristics with respect to a wide variety of missions of current and future interest. In addition, the recent development of magnetic shielding has led to a significant extension of their operational life potential. But the physics underlying the behavior of Hall thrusters remains very complex and not fully understood yet. Consequently, models attempting to describe the involved physical processes based on first principles have always proved difficult to develop and scarcely useful as tools that could guide the design process. Fortunately enough, modern Hall thrusters were developed through of a lengthy process of gradual refinement in which the main physical processes involved were brought to a satisfactory trade-off. The design of new thrusters can therefore be based on the capability to describe how the thruster characteristics could change with respect to a reference device based on suitably defined scaling criteria. The aim of this work is to propose an improved scaling methodology, especially intended for high-power Hall thrusters, which explicitly includes the effects of magnetic shielding. In the following, we firstly introduce a phenomenological model for the functioning of magnetically shielded Hall thruster. Then, after a quick review of mathematical formalism behind scaling, we describe the scaling procedure. The results obtained by its application are in excellent agreement with the empirical data collected in a specially created high-power Hall thruster database. Lastly, the possibility to obtain performance maps at constant discharge power and use them as a designing tool is described.