Magnetic Shielding of the Acceleration Channel Walls in a Long-Life Hall Thruster

Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.; Goebel, Dan M.; Grys, Kristi de; Mathers, Alex

doi:10.2514/6.2010-6942

Cited by 62 publications

(39 citation statements)

References 26 publications

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“…Numerical simulations performed at JPL with the Hall2De code [19] showed that the BPT-4000 had experienced erosion of the BN walls at rates typical to other Hall thrusters until a certain magnetic field topology was exposed close to the walls near the thruster exit plane that significantly reduced the energy and flux of the ions hitting the wall. This effect has been named magnetic shielding [17] and independently verified by modifying another laboratory Hall thruster at JPL to produce the required magnetic topology at the wall [20] to achieve very low erosion rates. Extensive theoretical and experimental efforts have gone into explaining magnetic shielding physics and demonstrating that this effect reduces the erosion of the BN walls by as much as a factor of 1000 [21]- [23].…”

mentioning

confidence: 97%

“…After the discovery that the erosion of the BN walls in the BPT-4000 Hall thruster designed and developed by Aerojet had essentially stopped after 5600 h of operation during lifetesting [16], an extensive investigation into the mechanism responsible for this effect was initiated at JPL [17], [18]. The erosion of the BN wall in Hall thrusters occurs due to sputtering of the surface by energetic ion bombardment from the plasma in the thruster.…”

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confidence: 99%

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Conducting Wall Hall Thrusters

Goebel¹,

Hofer

Mikellides³

et al. 2015

IEEE Trans. Plasma Sci.

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A unique configuration of the magnetic field and channel geometry near the wall of Hall thrusters, called magnetic shielding, has recently demonstrated the ability to significantly reduce the erosion of the boron nitride (BN) walls and extend the life of Hall thrusters by orders of magnitude. The ability of magnetic shielding to minimize interactions between the plasma and the discharge chamber walls in regions where erosion typically occurs has for the first time enabled the replacement of insulating walls with conducting materials without loss in Hall thruster performance. It is important to note that this is not a thruster with anode layer (TAL) where the walls are at or near cathode potential, but is a Hall thruster configuration where the walls are near the anode potential. The BN rings in the 6-kW H6 Hall thruster were replaced with graphite that self-biased to near the anode potential during operation. The thruster efficiency remained over 60% (within 2% of the baseline BN configuration) with a small decrease in thrust and increase in Isp typical of magnetically shielded Hall thrusters. The graphite wall temperatures decreased significantly compared with both shielded and unshielded BN configurations, leading to the potential for higher power operation. Eliminating ceramic walls makes it simpler and less expensive to fabricate a thruster to survive launch loads, and the graphite discharge chamber radiates more efficiently, which increases the power capability of the thruster compared with conventional Hall thruster designs.Index Terms-Hall effect devices, plasma propulsion.

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confidence: 97%

mentioning

confidence: 99%

Conducting Wall Hall Thrusters

Goebel¹,

Hofer

Mikellides³

et al. 2015

IEEE Trans. Plasma Sci.

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“…26,27 The thrusters are assumed to incorporate recently developed technologies which mitigate channel wall erosion so that no additional thrusters need to be added because of propellant throughput limitations. 28,29 The asteroid retrieval mission concept requirements for a 10-kW, 3000-s Hall thruster represent a capability that could readily be developed.…”

Section: B Electric Propulsion (Ep) Subsystemmentioning

confidence: 99%

Spacecraft Conceptual Design for Returning Entire Near-Earth Asteroids

Brophy¹,

Oleson²

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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In situ resource utilization (ISRU) in general, and asteroid mining in particular are ideas that have been around for a long time, and for good reason. It is clear that ultimately human exploration beyond low-Earth orbit will have to utilize the material resources available in space. Historically, the lack of sufficiently capable in-space transportation has been one of the key impediments to the harvesting of near-Earth asteroid resources. With the advent of high-power (or order 40 kW) solar electric propulsion systems, that impediment is being removed. High-power solar electric propulsion (SEP) would be enabling for the exploitation of asteroid resources. The design of a 40-kW end-of-life SEP system is presented that could rendezvous with, capture, and subsequently transport a 1,000-metric-ton near-Earth asteroid back to cislunar space. The conceptual spacecraft design was developed by the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team at the Glenn Research Center in collaboration with the Keck Institute forSpace Studies (KISS) team assembled to investigate the feasibility of an asteroid retrieval mission. Returning such an object to cislunar space would enable astronaut crews to inspect, sample, dissect, and ultimately determine how to extract the desired materials from the asteroid. This process could jump-start an entire ISRU industry.

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“…The second is to provide baseline data on existing thrusters prior to planned modifications that utilize a magneticallyshielded design for long life. 8 The third purpose is to provide experimental data for validation of ongoing modeling efforts at GRC and the Jet Propulsion Laboratory (JPL). 9 To accomplish these goals, an electrostatic probe array was deployed to interrogate the near-field plume of the NASA-457Mv2 Hall thruster from approximately 0.1 -2 mean thruster diameters (D T,m ) downstream of the thruster exit plane.…”

Section: Introductionmentioning

confidence: 99%

Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-457Mv2 Hall Thruster

Shastry¹,

Huang²,

Herman³

et al. 2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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In order to further the design of future high-power Hall thrusters and provide experimental validation for ongoing modeling efforts, plasma potential and Langmuir probe measurements were performed on the 50-kW NASA-457Mv2. An electrostatic probe array comprised of a near-field Faraday probe, single Langmuir probe, and emissive probe was used to interrogate the near-field plume from approximately 0.1 -2.0 mean thruster diameters downstream of the thruster exit plane at the following operating conditions: 300 V, 400 V and 500 V at 30 kW and 500 V at 50 kW. Results have shown that the acceleration zone is limited to within 0.4 mean thruster diameters of the exit plane while the hightemperature region is limited to 0.25 mean thruster diameters from the exit plane at all four operating conditions. Maximum plasma potentials in the near-field at 300 and 400 V were approximately 50 V with respect to cathode potential, while maximum electron temperatures varied from 24 -32 eV, depending on operating condition. Isothermal lines at all operating conditions were found to strongly resemble the magnetic field topology in the high-temperature regions. This distribution was found to create regions of high temperature and low density near the magnetic poles, indicating strong, thick sheath formation along these surfaces. The data taken from this study are considered valuable for future design as well as modeling validation. Nomenclature= mean thruster diameter I cap = capacitive current = anode mass flow rate P d = discharge power T = thrust T e = electron temperature η a = anode efficiency

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Magnetic Shielding of the Acceleration Channel Walls in a Long-Life Hall Thruster

Cited by 62 publications

References 26 publications

Conducting Wall Hall Thrusters

Conducting Wall Hall Thrusters

Spacecraft Conceptual Design for Returning Entire Near-Earth Asteroids

Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-457Mv2 Hall Thruster

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