Michael Brukardt

Observations of single-pass ion cyclotron heating in a trans-sonic flowing plasma

The VAriable Specific Impulse Magnetoplasma Rocket (VASIMR®) is a high power electric spacecraft propulsion system, capable of Isp/thrust modulation at constant power [F. R. Chang Diaz et al., Proceedings of the 39th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 8–11 Jan. 2001]. The VASIMR® uses a helicon discharge to generate plasma. This plasma is energized by an rf booster stage that uses left hand polarized slow mode waves launched from the high field side of the ion cyclotron resonance. In the experiments reported in this paper, the booster uses 2–4 MHz waves with up to 50 kW of power. This process is similar to the ion cyclotron heating (ICH) in tokamaks, but in the VASIMR® the ions only pass through the resonance region once. The rapid absorption of ion cyclotron waves has been predicted in recent theoretical studies. These theoretical predictions have been supported with several independent measurements in this paper. The single-pass ICH produced a substantial increase in ion velocity. Pi...

Recent Improvements In Ionization Costs And Ion Cyclotron Heating Efficiency In The VASIMR Engine

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.

Progress Toward the Development of a 50 kW VASIMR Engine

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.

VELOCITY PHASE SPACE STUDIES OF ION DYNAMICS IN THE VASIMR ENGINE

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.

VASIMR ® VX-200: High power electric propulsion for space transportation beyond LEO

(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 (RPAs), 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.

Hall Thruster and VASIMR VX-100 Force Measurements Using A Plasma Momentum Flux Sensor

The accuracy of a plasma impact force sensor was compared to that of the more commonly used inverted pendulum thrust stand using a 5 kW Xe Hall effect thruster (HET). An improved plasma momentum flux sensor (PMFS) was designed and constructed based on a previous design. Real-time force measurements were made with both the PMFS and the inverted pendulum thrust stand. The PMFS measured the force exerted onto it from the HET exhaust plume with a resolution of 0.1 mN, and an average discrepancy of 2% compared to thrust stand measurements. Experiments were completed using a 9 m by 6 m cylindrical vacuum chamber. The total force from the HET was modulated from 34 mN to 356 mN by varying both the anode voltage, from 150 V to 500 V, and the neutral Xe gas flow rate from 5 mg/s to 15 mg/s. Initial force measurements from the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) VX-100 are analyzed and compared to RPA data.

High Power Electric Propulsion Using VASIMR (TM): Results from Flight Prototypes

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.

High Power Ion Cyclotron Heating In the VASIMR Engine

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 high power single-pass ICRH ion acceleration data, with emphasis on the most recent results.

The VASIMR(TM) VX-100 Engine: Next Step to High Power Electric Propulsion

[Abstract] The Variable Specific Impulse Magnetoplasma Rocket ( VASIMR™ ) is a high power magnetoplasm a 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 mag netic 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 interfe rometry 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 t he fact that VASIMR™ is now being developed by private enterprise. The new VX -100 machine is described. The results from recent ionization cost and ICRH experiments in the VX -100 are presented.

VASIMR(TM): A Private Enterprise Solution to Space Transportation Beyond LEO

[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.