Parameterization of magnetic nozzle flow physics for an in-space propulsion application

摘要

The efficiency of a magnetic nozzle in converting thermal energy into directed axial energy is dependent on several factors, most notably on how and where the plasma separates or "detaches" from the nozzle. A detailed knowledge of the physics of this detachment process is presently lacking, but is necessary in order to optimize magnetic nozzle design for in-space applications. In an effort toward studying detachment computationally, we wish to first establish an appropriate mathematical model for the nozzle flow physics. In this work, we perform an order of magnitude analysis of the Boltzmann equation in terms of characteristic length scales for an Argon plasma. From this analysis, we create a parameter map of the relevant Argon physics in terms of temperature and density. We apply our analysis to examine the magnetic nozzle flow physics of the latest VASIMR rocket, the VX-200. We conclude that a fluid approximation is an appropriate mathematical model for the VX-200 system. This conclusion is valid if at least tensorial resistivity is included in the model near the exit plane of the rocket and further downstream local electric field effects are also included.