VASIMR Vx-100: High Power Electric Propulsion for Space Transportation Beyond LEO

Abstract

(Abstract) 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 resonance 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. 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 opportunities and challenges of this situation will be reviewed. VASIMR™ was originally designed to serve as the sustainer engines for the manned Mars mission, for which it remains one of the leading candidate systems. A number of other uses of the VASIMR™ have been studied in some detail, including robotic missions to the outer planets, ISSO reboost, station keeping and sustained maneuvering of robotic craft in Earth orbit, and lunar cargo hauling. We will explore the latter in this paper. A number of studies have illustrated the cost and mass efficiency of solar-electric propulsion as an alternative to chemical propulsion for hauling cargo from low Earth orbit to low lunar orbit; recent studies considered the Hall thruster in this application. Here, we present the results of a payload vs. specific impulse trade study for a six-month Earth-Moon transit time, and compare the technical and economic features of the VASIMR™ technology to other electric thrusters for this application.