Experimental status of the development of a variable specific impulse magnetoplasma rocket

The Advanced Space Propulsion Laboratory (ASPL) is developing a Variable Sp ecific Impulse Magnetoplasma Rocket(VASIMR)(1) using a Radio Frequency (RF) heated magnetic mirror operated asymmetrically. The system comprises of th ree stages: 1) plasma ionization and injection into the magnetic system; 2) ion heating by action of Ion Cyclotron Resonance Heating (ICRH); 3) plasma exhaust through a magnetic nozzle. The central experimental device is a sm all versatile tandem mirror configured system. The system can also be easil y reconfigured to operate as a simple mirror. The total length of the devic e is 3.2 m, and the maximum magnetic field is 3.0 T. The exhaust end connec ts to a 5 m(3) vacuum chamber where we are installing a 40,000 liter/second pumping capacity. Radio frequency power is available at approximately 3 MH z at up to 200 kW. A set of plasma diagnostics is being developed and insta lled, starting with two fast reciprocating probes, one quadruple Langmuir a nd one Mach(2). We are now evaluating the use of a helicon(3) RF plasma sou rce for an efficient ionization stage of the system. Initial results from e xperiments using a single double-half turn antenna are presented. In additi on, we are exploring the use of a Lorentz Force Accelerator (LFA) as a plas ma injector source.(4).