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.

[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-50 using deuterium, neon and argon plasma during 2006. 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.

In the Advanced Space Propulsion Laboratory (ASPL) helicon experiment (VX-10) we have measured a plasma flux to input gas rate ratio near 100% for both helium and deuterium at power levels up to 10 kW. Recent results at Oak Ridge National Laboratory (ORNL) show enhanced efficiency operation with a high power density, over 5 kW in a 5 cm diameter tube. Our helicon is presently 9 cm in diameter and operates up to 10 kW of input power. The data here uses a Boswell double-saddle antenna design with a magnetic cusp just upstream of the antenna. Similar to ORNL, for deuterium at near 10 kW, we find an enhanced performance of operation at magnetic fields above the lower hybrid matching condition.

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 review 3 years of single-pass ICRH ion acceleration data. During this interval, the available power to the helicon ionization stage has increased from 3 to 20 kW. The increased plasma density has produced increased plasma loading of the ICRH antenna and significant improvements in antenna coupling efficiency and in ion heating efficiency. We explored the details of the ion dynamics in a deuterium exhaust plasma using ~19 kW of RF power to the helicon ionization stage and 1.3 kW to the ICRH acceleration stage. Owing to significant reductions in ionization cost, the total ion flux in the exhaust plasma is an order of magnitude greater than the flux obtained during the experiments that were reported as recently as November of 2004. In this high-density plasma, the available energy per ion is reduced compared to last year, but the booster efficiency of the ICRH process has increased. Ion energization of ~17 eV/ion has been demonstrated in this higher flux flowing plasma. This energy increase corresponds to a booster efficiency (ηb) of 67%, in agreement with model predictions. Results also confirm conversion of transverse ion motion to axial motion via conservation of the first adiabatic invariant.

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power, radio frequency-driven magnetoplasma rocket, capable of Isp/thrust modulation at constant power. The physics and engineering of this device have been under study since 1980. The plasma is produced by an integrated helicon discharge. However, the bulk of the plasma energy is added in a separate downstream stage by ion cyclotron resonance heating (ICRH.) Axial momentum is obtained by the adiabatic expansion of the plasma in a magnetic nozzle. Exhaust variation in the VASIMR is primarily achieved by the selective partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. However, other complementary techniques are also being considered. A NASA-led, research effort, involving several teams in the United States, continues to explore the scientific and technological foundations of this concept. The research is multifaceted and involves theory, experiment, engineering design, mission analysis, and technology development. Experimentally, high density, stable plasma discharges have been generated in Helium, Hydrogen, Deuterium, Argon and Xenon. Theoretically, the dynamics of the magnetized plasma are being studied from kinetic and fluid approaches. Plasma acceleration by the magnetic nozzle and subsequent detachment has been demonstrated in numerical simulations. These results are presently undergoing experimental verification. Plasma properties of the helicon discharge and exhaust plasma have been measured under a variety of conditions. This paper will review the steps that have been taken to increase the power level in the experimental device from 4.5 kW to 50 kW.

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine concept is an RF-powered thruster scaleable to multi-megawatt power levels. The prototype at the Johnson Space Center consists of a helicon plasma source, an ion cyclotron resonant heating system, and a magnetic nozzle. Theoretical and computational predictions of the ion cyclotron heating system's effectiveness have been validated by the experimental results presented here. At modest power levels, the prototype thruster has demonstrated a continuously variable specific impulse spanning the range of 5,000 - 12,000 seconds. An upgrade to 50 kW thruster operation is in progress.

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power, radio frequency-driven magnetoplasma rocket, capable of Isp/thrust modulation at constant power. The physics and engineering of this device have been under study since 1980. The plasma is produced by an integrated helicon discharge. However, the bulk of the plasma energy is added in a separate downstream stage by ion cyclotron resonance heating (ICRH.) Axial momentum is obtained by the adiabatic expansion of the plasma in a magnetic nozzle. Exhaust variation in the VASIMR is primarily achieved by the selective partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. However, other complementary techniques are also being considered. A NASA -led, research effort, involving several teams in the United States, continues to explore the scientific and technological foundations of this concept. The research is multifaceted and involves theory, experiment, engineering design, mission analysis, and technology development. Experimentally, high density, stable plasma discharges have been generated in Helium, Hydrogen, Deuterium, Argon and Xenon. Theoretically, the dynamics of the magnetized plasma are being studied from kinetic and fluid approaches. Plasma acceleration by the magnetic nozzle and subsequent detachment has been demonstrated in numerical simulations. These results are presently undergoing experimental verification. Plasma properties of the helicon discharge and exhaust plasma have been measured under a variety of conditions. This paper will review the ion energy and velocity measurments obtained in 2002-2004 in a continuing series of performance optimization and design development studies and will outline plan and strategies for continued research.