VASIMR Performance Measurements at Powers Exceeding 50 kW and Lunar Robotic Mission Applications

The University of Houston, 77004, Houston, Texas, USA


Efficient plasma production and acceleration is observed in a new high power Variable Specific Impulse Magnetoplasma Rocket (VASIMR TM) experiment, the VX-100, using argon propellant. The Radio Frequency (RF) power exceeds 50 kW. A 100 % propellant utilization is achieved with ion fluxes up to 1.7×10 21 /sec. We measure an ionization cost of 80±10 eV per ion-electron pair. Bulk argon ion flow velocities are measured up to 20 km/s. Thrust values based on plasma exhaust measurements exceed 1 N. A 200 kW superconducting device, the VX-200, and 150 m 3 vacuum facility are described. We outline the operations concept for a solar-electric lunar cargo tug whose performance is extrapolated from the VX-100 experiment results. Due to the 5,000 second specific impulse of the VASIMR engine, the fraction of the initial mass in low Earth orbit (IMLEO) that arrives in low lunar orbit (LLO) is approximately double that of a chemical propulsion system that performs at a specific impulse of only 450 seconds. The effect of space photovoltaic power cost on the economic advantage of the solar-electric system is examined.

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    • "The exhaust velocities from VASIMR are expected to reach as high as 120 km/s [3] in final prototypes. For near-term applications of VASIMR, large solar arrays are expected to generate electric power for the rocket [4]. The VASIMR engine is depicted in Figure 1. "
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    ABSTRACT: The VASIMR propulsion system is an ion propulsion system for spacecraft that uses magnetic fields to accelerate plasma to produce thrust. Undesired heat produced in the helicon section of VASIMR must be monitored and removed safely to avoid damage to system components, especially when higher power operating regimes are explored. This article demonstrates a strategy for distributed temperature estimation, based on OES measurement, and a model where the states represent the distributed temperature profile. OES provides a noninvasive measurement technique, which can be used as an output "correction" term for a state-estimation scheme. In this application, it is shown that the 2048 OES channels recorded can be accurately represented by only three principal components for temperature estimation. Use of the principal components as corrector terms in the state-space model dramatically improve model accuracy and the capability of the model to recover from unknown initial conditions and multiple system input changes.
    IEEE control systems 01/2010; 29(6-29):15 - 25. DOI:10.1109/MCS.2009.934407 · 2.09 Impact Factor
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    ABSTRACT: torr for xenon. Ion number density, electron temperature, and electron energy distribution function measurements are taken at several axial and radial locations inside the device at each operating condition with a ratio-frequency-compensated Langmuir probe. The annularheliconplasmasourceischaracterizedoverarangeofappliedradiofrequencies(2-14MHz),magnetic field strengths (0-400 G), and radio frequency forward-power settings (100-1400 W) for both argon and xenon propellants. The peak ion number density measured in the annular helicon is 2:6 10 17 m 3 for argon and 2:4 10 17 m 3 for xenon at 1000 W of radio frequency power. The annular helicon electron energy distribution function peak and shape vary with the radio frequency, from a minimum of 3.7 eV at 13 MHz to a maximum of 15.0 eV at 11 MHz for argon propellant over the preceding operating conditions. Nomenclature Pinput = input power Pjet = jet power VD = discharge voltage Vnc = neutralizer coupling voltage � = plume divergence coefficient " = ionization cost � =e f ficiency � u = propellant utilization efficiency
    Journal of Propulsion and Power 09/2009; 25(5):1013-1019. DOI:10.2514/1.41403 · 0.87 Impact Factor
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    ABSTRACT: A superconducting Variable Specific Impulse Magnetoplasma Rocket (VASIMR®) experiment (VX-200) is in operation. This device demonstrates the spaceflight relevant VASIMR® technology at the 200 kW electrical power level, from DC to plasma jet. The VX-200 is a two stage system using a helicon for plasma production and ion cyclotron heating for the primary plasma acceleration (RF booster). Five key technology elements are combined in this integrated test. The first is the efficient and light weight conversion of DC electrical power (~ 400 VDC) to RF power. The helicon RF generator operates at power levels up to 40 kW with an efficiency of about 92% and the ICH RF generator operates at power levels up to 170 kW with an efficiency of 98%. The RF generator alpha is less than 1 kg/kW. The second element is a superconducting high field (2 T) magnet that is a cryogen-free low temperature (5 K) superconductor. Though not intended to be flight-like, it is a significant step toward realizing a flight version. The third element is the high field helicon plasma source operating in a superconducting system. We have measured an argon plasma jet with an energy cost to extract an electron-ion pair of 78 ± 11 eV/ion at 32 kW and flow rate of 135 mg/s. The fourth element is the RF booster acceleration stage. A record power of 149.2 kW was coupled to an interim reduced magnetic field configuration for a test of the RF booster power train. Finally, the VX-200 operates in a large 150 m3 vacuum chamber with over 100,000 l/s of cryo-pumping to accurately measure the plasma flow properties in the plume.
    31st International Electric Propulsion Conference, University of Michigan, Ann Arbor, MI; 09/2009
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