Figure 1. Plasma lens design: Magnetic field topography (numerically simulated) of the NASA-173Mv1 at several internal trim coil currents and constant inner and outer coil currents of 5 A. (From ref. 2).
Figure 2. Photograph of the 6-kW Hall thruster during operation at nominal conditions of 300 V and 20 mg/s (6 kW). (From ref. 4.)
Figure 3. Anode flow uniformity design: FLUENT simulations of the mass flux at the anode exit for the NASA-173M and 6-kW Hall thruster (from ref. 4).
The exact power level that qualifies as "high-power" in Hall thrusters is a shifting target.
In the 1990s anything over a kilowatt would have been considered high power, yet with the advent of thrusters like the 50-kW NASA 457M and more recently nested thrusters like the X2, the bar has shifted and now it would be fair to say that "high-power" begins in the 5-10 kW range, if not higher.
This increase in electrical power is largely driven by a decrease in the cost of onboard electrical power for spacecraft and the ever-present desire for increased thrust, which requires an increase in mass flow rate and thus electrical current as each propellant atom is ionized and ejected.
In contrast the voltage range of Hall thrusters has remained surprisingly steady over the past few decades, residing generally in the 300 V range up until the early 2000s, when research at PEPL outlined improved magnetic circuit designs for efficient operation at higher voltages (see ref. 2).
While Hall thrusters are still often run in the low hundreds of volts, operation at high efficiency up to 1000 V has been demonstrated at PEPL, approaching a domain traditionally reserved for gridded ion thrusters.
For the last decade PEPL has designed, built, and extensively researched a family of 5-6 kW single channel thrusters, beginning with the 5-kW class P5 (co-developed with the AFRL, see ref. 1), followed by the 5-kW class NASA 173Mv1 and v2 (co-developed with NASA Glenn, see ref. 2), and more recently with a 6-kW laboratory model Hall thruster (co-developed with the AFRL and NASA JPL, see ref. 3).
These thrusters have demonstrated improvements in magnetic field design and anode flow uniformity (see ref. 4) that push anode efficiencies up to nearly 70%. Development and testing of high power nested channel Hall thrusters such as the X2 and the X3 are further pushing the boundaries of high power Hall thrusters.
Selected Relevant Publications
Gulczinski, F. S., "Examination of the Structure and Evolution of Ion Energy Properties of a 5 kW Class Laboratory Hall Effect Thruster at Various Operational Conditions,"
Ph.D. Dissertation, University of Michigan, 1999.
Hofer, R. R., "Development and Characterization of High-Efficiency, High-Specific Impulse Xenon Hall Thrusters,"
Ph.D. Dissertation, University of Michigan, 2004.
Haas, J. M., Hofer, R. R., Brown, D. L., Reid, B. M., and Gallimore, A. D., "Design of a 6-kW Hall Thruster for High Thrust/Power Investigation,"
Presented at the 54th JANNAF Propulsion Meeting, Denver, CO, May 14-17, 2007.
Reid, B. M., "The Influence of Neutral Flow Rate in the Operation of Hall Thrusters,"
Ph.D. Dissertation, University of Michigan, 2009.