Generation and Sustainment of a Plasma Magnetic Sail

Plasma sail propulsion based on the plasma magnet is a unique system that taps the ambient energy of the solar wind with minimal energy and mass requirements. The coupling to the solar wind is made through the generation of a large-scale ($\sim >$ 30 km) dipolar magnetic field. Unlike the original magnetic sail, the coil currents are conducted in a plasma rather than a superconducting coil with the mass of the sail is reduced by orders of magnitude. Unlike a solid magnet or sail, the plasma magnet expands with falling solar wind pressure to provide constant thrust. The plasma magnet consists of a pair of polyphase coils that produce a rotating magnetic field that drives the necessary currents in the plasma to inflate and maintain the large-scale magnetic structure. The plasma magnet is deployed by the Lorentz self-force expanding outward until the expansion is halted by the solar wind pressure. The results from the initial experiments demonstrated that the appropriate high $\beta $, high current plasma can be created and sustained in the geometry suitable for the space application of the concept. Sufficient current was generated in the plasma magnet to produce a plasma magnetosphere of sufficient pressure to push out well beyond the 30 km scale required. Work is now underway to measure the thrust imparted to the plasma magnet by a large scale surrogate solar wind source.