Improved Efficiency and Throttling Range of the VX-200 Magnetoplasma Thruster

Abstract

Testing of the Variable Specific Impulse Magnetoplasma Rocket VX-200 engine was performed over a wide throttle range in a 150 m 3 vacuum chamber with sufficient pumping to permit exhaust plume measurements at argon background pressures less than 1 × 10 −3 Pa (1 × 10 −5 torr) during firings, ensuring charge-exchange mean free paths longer than the vacuum chamber. Measurements of plasma flux, radio frequency power, propellant flow rate, and ion kinetic energy were used to determine the ionization cost of argon and krypton in the helicon discharge. Experimental data on ionization cost, ion fraction, exhaust plume expansion angle, thruster efficiency, and thrust are presented that characterize the VX-200 engine performance over a throttling range from 15 to 200 kW radio frequency power. A semiempirical model of the thruster efficiency as a function of specific impulse indicates an ion cyclotron heating efficiency of 85 7%. Operation at a total radio frequency coupled power level of 200 kW yields a thruster efficiency of 72 6% at a specific impulse of 4900 300 s with argon propellant. A high thrust-to-power operating mode was characterized over a wide parameter space with a maximum thrust-to-power ratio of 51 5 mN∕kW at a specific impulse of 1660 100 s for a ratio of ion cyclotron heating radio frequency power to helicon radio frequency power of 0.7∶1.

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

“…In this case, the displacement is only ∼10 −4 cm. If, however, a 0.005-cm diameter filament was used in a magnetic field of 20,000 G, such as in the variable specific impulse magnetoplasma rocket (VASIMR) [108], the displacement would be ∼3 cm, larger that the size of the probe and resulting in the probe being distorted to the point of destruction. The displacement should be approximately less than a filament diameter to ensure that distortion from the magnetic field is not significant.…”

New Low-Power Plasma Thruster for Nanosatellites

“…As mentioned before, W depends on both the propellant and the device, but values of ∼ 60 eV are typical. 18 Thus, the thruster efficiency is expected to be 10% -40%. Thrust (T ) can then be calculated as T = 2η t P rf I sp g 0…”

“…VASIMR is a 200kW thruster that uses a helicon plasma source to heat the electrons and ion cyclotron resonance to heat the ions, both of which expand through a magnetic nozzle to produce thrust. 18 This device has been designed for a next generation of spacecraft, being approximately 2 m long and requires far more power than conventional spacecraft can generate. Laboratory helicons are typically require power in the low kW range, which is on par with many established Hall thrusters and ion engines, and various groups have begun developing helicon thrusters on this scale.…”

Review of Helicon High-Density Plasma: Production Mechanism and Plasma/Wave Characteristics

“…In this system, the generated plasma is energized further by an ion cyclotron heating (ICH) RF stage [258] that uses left-hand polarized slow-mode waves launched from the high field side of the ion cyclotron resonance, and useful thrust is produced as the plasma accelerates in an expanding magnetic field [259]. In recent studies, the thruster efficiency and thrust power of a high-power VASIMR prototype have been measured at a level of 200 kW RF input power [258,[260][261][262][263].…”