Investigation of Plasma Detachment from a Magnetic Nozzle

Abstract

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) electric space propulsion concept currently under development by the Ad Astra Rocket Company utilizes a magnetic field to confine a propellant plasma. The energetic ions in the plasma are converted into a directed exhaust flow by a magnetic nozzle. The interaction between the diverging magnetic field and the escaping plasma plume is of interest both because of its technological importance in this application and its relationship to naturally occuring phenomena in the field of space plasma physics. The research presented here was carried out at the Propulsion Research Center of Marshall Space Flight Center. The focus of this effort is the measurement of the time dependent effect of a plasma plume on the vacuum magnetic field geometry in a simulated magnetic nozzle. Data was gathered with magnetic field probes constructed at the Royal Institute of Technology in Stockholm, Sweden. This data was analyzed and compared to published theoretical descriptions of plasma detachment from a magnetic nozzle. The results of that analysis are presented here.