Experimental investigation of the mini-magnetospheric plasma propulsion prototype

Mini-Magnetospheric Plasma Propulsion (M2P2) seeks the creation of a large-scale (10 km radius) magnetic wall or bubble (i.e. a magnetosphere) by the electromagnetic inflation of a small-scale (20 cm radius) dipole magnet. The inflated magnetosphere will intercept the, solar wind and thereby provide high-speed propulsion with modest power and fuel requirements due to the gain provided by the ambient medium. Magnetic field inflation is produced by the injection of plasma onto the dipole magnetic field eliminating the need for large mechanical structures and added material weight at launch. For successful inflation of the magnetic bubble a beta near unity must be achieved along the imposed dipole field. This is dependent of the plasma parameters that can be achieved with a plasma source that provide continuous operation at the desired power levels of 1 to 2 kilowatts. Over the last two years I have been developing a laboratory prototype to demonstrate the inflation of the magnetic field under space-like conditions. In this thesis I will present some of the latest results from the prototype development at the University of Washington and show that the prototype can produce high ionization efficiencies while operating in near space-like neutral background pressures producing electron temperatures of a few tens of electron volts. Plasma characteristics from the helicon source region and in the dipole equator show a beam like plasma that is generated from the helicon source. Some magnetic inflation dynamics are noted, but magnitudes are much lower than modeling predicts. It is believed that the helicon source is generating a field-aligned electron current, which adds to the plasma confinement and possibly hampering inflation. Additionally, the experimental results indicate that wall interactions with the vacuum chamber also have a negative effect. Possible solutions to overcome low plasma betas in the equatorial region are discussed.