Abstract
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.
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