Challenges in the development and verification of first-principles models in Hall-effect thruster simulations that are based on anomalous resistivity and generalized Ohm’s law*

Since the inception of the Hall-effect thruster more than five decades ago, many theories have been proposed about the source(s) of the anomalous cross-field transport that is known to occur in these devices. Yet, none of these theories has been implemented in two-dimensional (2D) ( r – z ) simulations and successfully predicted the behavior of the discharge and the erosion of a thruster over different operating conditions and geometries. We present results from numerical experiments with a 2D ( r – z ) axisymmetric hydrodynamics code that show the plasma solution is relatively insensitive to very large variations in the anomalous transport in some regions of the discharge channel and near-plume. Because the changes of the plasma properties in these regions can be too small or impossible to detect in the laboratory by conventional diagnostics, the verification of a transport model becomes very challenging. Hence, without more advanced diagnostics and improved numerical models, comparisons between plasma measurements and simulation results can lead to wide-ranging theories and scalings of the anomalous resistivity.