Investigation of the Effects of Facility Background Pressure on the Performance and Operation of the High Voltage Hall Accelerator

Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Spektor, Rotislav

doi:10.2514/6.2014-3707

Cited by 25 publications

(30 citation statements)

References 10 publications

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“…However, as the Hall thruster power and efficiency increase, a significant departure from predicted on-orbit operation based on ground test and simulation data has brought into question the validity of established pressure limits for thruster qualification. Typical pressures seen in research and development vacuum facilities during thruster operation are ∼1-5 × 10 −5 torr, with world-class test and evaluation facilities such as the NASA John H. Glenn Research Center's Vacuum Facility 5 approaching low 10 −6 or middle 10 −7 torr, depending on the propellant flow rate of the thruster [8]. Even these lower pressures are orders of magnitude higher than the less than 1 × 10 −10 torr seen at geostationary orbit.…”

Section: Introductionmentioning

confidence: 99%

Background Pressure Effects on Ion Velocity Distributions in an SPT-100 Hall Thruster

MacDonald-Tenenbaum

Pratt²,

Nakles³

et al. 2019

Journal of Propulsion and Power

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Increased background pressure in vacuum chamber test facilities as compared to on-orbit operation has been shown to influence the operation of electric propulsion devices such as Hall thrusters. This study aims to elucidate the impact of pressure on the ionization and acceleration mechanisms in a stationary plasma thruster, model SPT-100 Hall thruster, using time-averaged and time-resolved laser-induced fluorescence velocimetry. The results are compared for the thruster operating at an applied 300 V (∼4.25 A), with vacuum facility background pressures ranging from 1.7 × 10 −5 to 8.0 × 10 −5 torr. Time-averaged measurements reveal that, in general, an upstream shift in the position of the ionization and acceleration regions occurs as the facility pressure is increased above the nominal 1.7 × 10 −5 torr. Time-resolved measurements, implemented using a sample-hold scheme with 1 μs resolution, emphasize that similar acceleration profiles are present within the Hall thruster discharge channel regardless of background pressure. Measurements taken at 3.5 × 10 −5 torr, where the facility background neutral density is similar to the neutral density emitted from the thruster, unexpectedly show increased ion acceleration over the next highest pressure condition at 5.0 × 10 −5 torr. These results indicate a not-yet well defined balance of the impacts of neutral ingestion, classical and turbulent electron transport on thruster operation, and that the ratio of the background to thruster neutral density is a more relevant benchmark than background pressure alone when evaluating Hall thruster operation.

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Section: Introductionmentioning

confidence: 99%

Background Pressure Effects on Ion Velocity Distributions in an SPT-100 Hall Thruster

MacDonald-Tenenbaum

Pratt²,

Nakles³

et al. 2019

Journal of Propulsion and Power

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show abstract

“…15 During the test, thrust, current-voltage (I-V) characteristics, and a number of plasma diagnostics were implemented to study the effect of varying the facility background pressure on thruster operation. 16 These diagnostics include thrust stand, Faraday probe, ExB probe, and retarding potential analyzer. 17 The test results indicated a rise in thrust and discharge current with background pressure.…”

Section: High Voltage Hall Acceleratormentioning

confidence: 99%

Status of propulsion technology development under the NASA In-Space Propulsion Technology program

Anderson

Kamhawi²,

Patterson³

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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Since 2001, the In-Space Propulsion Technology (ISPT) program has been developing and delivering in-space propulsion technologies for NASA's Science Mission Directorate (SMD). These in-space propulsion technologies are applicable, and potentially enabling for future NASA Discovery, New Frontiers, Flagship and sample return missions currently under consideration. The ISPT program is currently developing technology in three areas that include Propulsion System Technologies, Entry Vehicle Technologies, and Systems/Mission Analysis. ISPT's propulsion technologies include: 1) the 0.6-7 kW NASA's Evolutionary Xenon Thruster (NEXT) gridded ion propulsion system; 2) a 0.3-3.9kW Halleffect electric propulsion (HEP) system for low cost and sample return missions; 3) the Xenon Flow Control Module (XFCM); 4) ultra-lightweight propellant tank technologies (ULTT); and 5) propulsion technologies for a Mars Ascent Vehicle (MAV). The NEXT Long Duration Test (LDT) recently exceeded 50,000 hours of operation and 900 kg throughput, corresponding to 34.8 MN-s of total impulse delivered. The HEP system is composed of the High Voltage Hall Accelerator (HIVHAC) thruster, a power processing unit (PPU), and the XFCM. NEXT and the HIVHAC are throttle-able electric propulsion systems for planetary science missions. The XFCM and ULTT are two component technologies which being developed with nearer-term flight infusion in mind. Several of the ISPT technologies are related to sample return missions needs: MAV propulsion and electric propulsion. And finally, one focus of the Systems/Mission Analysis area is developing tools that aid the application or operation of these technologies on wide variety of mission concepts. This paper provides a brief overview of the ISPT program, describing the development status and technology infusion readiness.

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“…Previous investigations in other thrusters have observed that the acceleration zone and plasma recede further into the channel towards the anode with elevated facility pressure. 19,[28][29][30][31][32] In particular, this shift was observed to cause increased electron temperatures along the channel walls of the HiVHAc Hall thruster. 19 It is possible that a similar shift in the plasma is occurring towards the anode, resulting in slightly elevated temperatures at higher pressure.…”

Section: A Axial Profiles Under Nominal Conditionsmentioning

confidence: 99%

Near-Surface Plasma Characterization of the 12.5-kW NASA TDU1 Hall Thruster

Shastry

Huang²,

Kamhawi³

2015

51st AIAA/SAE/ASEE Joint Propulsion Conference

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To advance the state-of-the-art in Hall thruster technology, NASA is developing a 12.5-kW, high-specific-impulse, high-throughput thruster for the Solar Electric Propulsion Technology Demonstration Mission. In order to meet the demanding lifetime requirements of potential missions such as the Asteroid Redirect Robotic Mission, magnetic shielding was incorporated into the thruster design. Two units of the resulting thruster, called the Hall Effect Rocket with Magnetic Shielding (HERMeS), were fabricated and are presently being characterized. The first of these units, designated the Technology Development Unit 1 (TDU1), has undergone extensive performance and thermal characterization at NASA Glenn Research Center. A preliminary lifetime assessment was conducted by characterizing the degree of magnetic shielding within the thruster. This characterization was accomplished by placing eight flush-mounted Langmuir probes within each discharge channel wall and measuring the local plasma potential and electron temperature at various axial locations. Measured properties indicate a high degree of magnetic shielding across the throttle table, with plasma potential variations along each channel wall being ≤ 5 V and electron temperatures being maintained at ≤ 5 eV, even at 800 V discharge voltage near the thruster exit plane. These properties indicate that ion impact energies within the HERMeS will not exceed 26 eV, which is below the expected sputtering threshold energy for boron nitride. Parametric studies that varied the facility backpressure and magnetic field strength at 300 V, 9.4 kW, illustrate that the plasma potential and electron temperature are insensitive to these parameters, with shielding being maintained at facility pressures 3X higher and magnetic field strengths 2.5X higher than nominal conditions. Overall, the preliminary lifetime assessment indicates a high degree of shielding within the HERMeS TDU1, effectively mitigating discharge channel erosion as a life-limiting mechanism.

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Investigation of the Effects of Facility Background Pressure on the Performance and Operation of the High Voltage Hall Accelerator

Cited by 25 publications

References 10 publications

Background Pressure Effects on Ion Velocity Distributions in an SPT-100 Hall Thruster

Background Pressure Effects on Ion Velocity Distributions in an SPT-100 Hall Thruster

Status of propulsion technology development under the NASA In-Space Propulsion Technology program

Near-Surface Plasma Characterization of the 12.5-kW NASA TDU1 Hall Thruster

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