Plasma expansion in a paraxial magnetic nozzle

Summary form only given. Several space propulsion systems have been proposed that could possibly realize mass efficiency gains over prior systems. These propulsion systems utilize magnetic nozzles with strong magnetic fields to shape a plasma flow into a directed jet. The ability of strongly magnetized plasma to break free from the confining field in these systems is critical for efficient momentum transfer to the plasma exhaust. MHD theory and simulation each predict that momentum will be transferred once the flow kinetic energy density WK is greater than WB the magnetic field energy density. An experiment is being conducted at NASA Marshall Space Flight Center which tests this theory. Multiple plasma sources and feed gasses are being used including hydrogen plasma in both a washer gun and helicon source. A paraxial magnetic nozzle guides the plasma with straight diverging field lines to the nozzle aperture. High flow velocities at the nozzle aperture suggest that the flow is super-Alfvenic at this point (WK > WB). Diagnostics used in the experiment to verify the effects of super-Alfvenic detachment include measurements from Hall probes, Langmuir probes, RF interferometer and flux loops