Progress in Experimental Research of the Vasimr Engine

The Advanced Space Propulsion Laboratory (ASPL) of NASA's Johnson Space Center is performing research on a Variable Specific Impulse MagnetoPlasma Rocket (VASIMR). The VASIMR is a high power, radio frequency (RF) driven magnetoplasma rocket, capable of very high exhaust velocities, > 100 km/s. A NASA-led research team involving industry, academia and government facilities is pursuing the development of this concept in the United States. The ASPL's experimental research focuses on three major areas: helicon plasma production, ion cyclotron resonant frequency (ICRF) acceleration and plasma expansion in a magnetic nozzle. The VASIMR experiment (VX-10) performs experimental research that demonstrates the thruster concept at a total RF power on the order of 10 kW. A flexible four-magnet system, with a 1.3 Tesla maximum magnetic field strength, allows axial magnetic field profile shape effects to be studied. Power generated at 10 – 50 MHz with about 3 kW is used to perform helicon plasma source development. A 3 MHz RF transmitter capable of 100 kW is available for ICRF experiments. The primary diagnostics are: gas mass flow controllers, RF input power, Langmuir probes, Mach probe, retarding potential analyzers (RPA), microwave interferometer, neutral pressure measurements and plasma light emission. In addition, many thermocouples are attached inside the vacuum chamber to measure heat loads around the plasma discharge.

Helicon research has been done with hydrogen, deuterium, helium, nitrogen, argon, xenon and mixtures of these gases. Optimization studies have been performed with the magnetic field axial profile shape, antenna geometry, gas flow rate, gas tube geometry and RF frequency. ICRF experiments have begun, primarily using a high density (> 10¹⁸/m³) helium helicon discharge as a target. Over 6 kW of power has been applied using a simple antenna array. The latest results of helicon and ICRF experiments will be presented.