Abstract:
Hall Thrusters are plasma propulsion devices with high potential for application in deep-space missions, in which they are required to have operating times in excess of 20,000 hours. Numerical simulations of the plasma discharge in these devices play an important role in design and pre-flight testing due to the time constraints associated with testing thrusters in vacuum facilities for extended periods of time. However, engineering codes, which track macroscopic plasma properties, have been unable to reproduce the experimentally measured specifics of the plasma discharge in Hall thrusters without the addition of a phenomenological "anomalous" term in the electron transport equations. It has been postulated by analysis and measurements that the turbulence generated by the "electron cyclotron drift instability" is the cause of the enhanced electron transport observed in Hall thrusters. We present an expression, based on kinetic theory and the notion of wave packets, for the evolution in time of the wave energy associated with the electron cyclotron drift instability as a function of position and wave number. We make reasonable assumptions to take moments of this equation with respect to the wave number and obtain a differential equation in time and space that can be solved concurrently with the motion equations implemented in our engineering code. Thus, we are able to produce for the first time a completely first-principles numerical code for the evolution of the plasma discharge in Hall thrusters. Preliminary results show that reasonable agreement with the plasma properties predicted by experimental measurements is obtained with this new code.
With Ira Katz, Ioannis G. Mikellides and Benjamin A. Jorns |