High Power Electric Propulsion Using VASIMR™: Results From Flight Prototypes

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR™) is a high power magnetoplasma rocket, capable of Isp/thrust modulation at constant power. The plasma is produced by a helicon discharge. The bulk of the energy is added by ion cyclotron region heating (ICRH.) Axial momentum is obtained by adiabatic expansion of the plasma in a magnetic nozzle. Thrust/specific impulse ratio control in the VASIMR ™ is primarily achieved by the partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. Ion dynamics in the exhaust were studied using probes, gridded energy analyzers (RPA’s), microwave interferometry and optical techniques. This paper will summarize results from high power ICRH experiments performed on the VX-100 using argon plasma during 2007, and technology demonstration from the VX-200. An overview of the way forward will be touched on briefly, with some emphasis on the fact that VASIMR ™ is now being developed by private enterprise. The new VX-200 machine is described. Nomenclature ηA = ICRH antenna efficienc