Advances in High Power Beamed Plasma Propulsion

Magnetic nozzles offer the ability to provide highly collimated plasma streams that increase thruster efficiency by maximizing conversion of thermal energy into directed energy. However, in order to ensure that the plasma becomes detached from the field lines, the plasma must become super-Alfvenic as it traverses the nozzle. If the plasma is also supersonic, self-focusing of the plasma can occur due to the modification of the magnetic field by induce plasma currents that cause the magnetic field lines to be dragged outwards with the plasma. In so doing the subsequent plasma encounters a more convergent magnetic field configuration as it leaves the nozzle, enhancing the collimation. These processes are demonstrated through computer simulations and verified using a high power helicon for the thruster. Increase in transit times of a factor of 33% are demonstrated with the density being substantially enhanced along the axis of the magnetic nozzle. The plasma beam is used to beam power into a distant system at the end of the chamber. This remotely powered thruster is shown to be able to support very high densities and with excellent collimation, albeit at reduced specific impulse but without any onboard power. This experiment demonstrates the ability of using a beamed plasma system to power the propulsion of a remote spacecraft. Such systems could substantially reduce the cost of orbital transfers from low Earth orbit to geosynchronous orbit and even for planetary transfer orbits.