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Wensheng Huang

Publications and source records attributed to Wensheng Huang.

26 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Ion Velocity Characterization of the 12.5-kW Advanced Electric Propulsion System Engineering Hall Thruster

During development testing of the 12.5-kW Advanced Electric Propulsion System engineering unit Hall thruster, which is magnetically shielded, a laser-induced fluorescence test was performed. During this test, a third medium-energy ion population was found near the inner front pole cover in addition to two low-energy counter-streaming ion populations that were found in previous testing. This newly found ion population matched in characteristics with the single population found near the outer front pole cover. The measured characteristics of the medium-energy ions matched the behavior expected of them if they were energized by a plasma wave with magnetized electrons, such as a lower hybrid wave. Comparison of the data from this test to prior tests showed that this engineering thruster had very similar ion characteristics as the precursor laboratory thruster. The acceleration zone was found to move upstream with increasing background pressure, decreasing anode flowrate, and increasing magnetic field strength. For the low-energy ions, the energy of the ions arriving at the inner pole did not vary noticeably with background pressure but did increase with increasing magnetic field strength and decreasing anode flow rate. For the medium-energy ions, the energy of the ions increased with decreasing background pressure, decreasing anode flow rate, and increasing magnetic field strength. Testing at different cathode flow fraction showed that the energy of the low-energy ions from the cathode decreased with increasing cathode flow.

Electric propulsion↗
NASA NTRSDate not supplied

The Side Plume of Magnetically Shielded Hall Thrusters

A combination of near-thruster laser-induced fluorescence and far-field plasma probe measurements collected from two magnetically shielded Hall thrusters have shown that there exist an independent ion population of medium-energy (on average, 60-190 eV) exiting out the side (60° to 100° from firing axis) of the thrusters. Studying the trends with background pressure and known discrepancies between the laser-induced fluorescence and far-field plasma probe data suggest that at zero pressure the side plume is likely to exhibit higher energy and lower density than at facility background pressures. The possibility that these ions were produced by the modified two-stream instability is explored and while the agreement is good, there are areas of notable disagreement. Based on the idea that production of the side plume and channel exit striations are due to the same plasma wave actions, a theory was explored that explains why striations form under certain circumstances but not others. Another theory, based on the idea that side plume production only occurs over certain portion of the global discharge oscillation cycle, was also explored and areas of disagreement were identified. While the exact mechanism for side plume acceleration remains unclear, if the theory behind side plume production is correct, then side plume can be expected to be present in a wide range of magnetically-shielded as well as non-shielded Hall thrusters.

Hall thruster↗
NASA NTRSDate not supplied

The Side Plume of Magnetically Shielded Hall Thrusters

A combination of near-thruster laser-induced fluorescence and far-field plasma probe measurements collected from two magnetically shielded Hall thrusters have shown that there exist an independent ion population of medium-energy (on average, 60-190 eV) exiting out the side (60° to 100° from firing axis) of the thrusters. Studying the trends with background pressure and known discrepancies between the laser-induced fluorescence and far-field plasma probe data suggest that at zero pressure the side plume is likely to exhibit higher energy and lower density than at facility background pressures. The possibility that these ions were produced by the modified two-stream instability is explored and while the agreement is good, there are areas of notable disagreement. Based on the idea that production of the side plume and channel exit striations are due to the same plasma wave actions, a theory was explored that explains why striations form under certain circumstances but not others. Another theory, based on the idea that side plume production only occurs over certain portion of the global discharge oscillation cycle, was also explored and areas of disagreement were identified. While the exact mechanism for side plume acceleration remains unclear, if the theory behind side plume production is correct, then side plume can be expected to be present in a wide range of magnetically-shielded as well as non-shielded Hall thrusters.

Electric propulsion↗
NASA NTRSDate not supplied

A Facility Effect Characterization Test of the BHT-6000 Hall Thruster

During the development of the BHT-6000 Hall thruster for flight on NASA’s Power and Propulsion Element, a facility effect test campaign was performed on an engineering unit of the thruster. Testing occurred in Vacuum Facility 5 at NASA Glenn Research Center. The goal of the test campaign was to characterize the behavior of the BHT-6000 Hall thruster as functions of facility effects such that the thruster’s in-flight behavior can be reasonably bounded. In particular, the behavior of the thruster with regard to the background pressure and electrical environment was tested. The background pressure was controlled by injecting supplemental propellant flow into the environment, while the electrical environment was controlled by biasing the facility beam dump. Thrust was found to remain constant over the tested range of pressures while specific impulse was found to increase slightly (1 to 1.5% over a range of up to 20 μTorr, depending on operating point). Plasma plume properties, particularly of ions exiting the side of the thruster, were found to be highly sensitive to pressure and may require pressures of less than a few μTorr for accurate measurements. The thruster was found to operate identically with changing beam dump bias voltage to within measurement uncertainties.

Electric propulsion↗
NASA NTRSDate not supplied

A Facility Effect Characterization Test of the BHT6000 Hall Thruster

During the development of the BHT-6000 Hall thruster for flight on NASA’s Power and Propulsion Element, a facility effect test campaign was performed on an engineering unit of the thruster. Testing occurred in Vacuum Facility 5 at NASA Glenn Research Center. The goal of the test campaign was to characterize the behavior of the BHT-6000 Hall thruster as functions of facility effects such that the thruster’s in-flight behavior can be reasonably bounded. In particular, the behavior of the thruster with regard to the background pressure and electrical environment was tested. The background pressure was controlled by injecting supplemental propellant flow into the environment, while the electrical environment was controlled by biasing the facility beam dump. Thrust was found to remain constant over the tested range of pressures while specific impulse was found to increase slightly (1 to 1.5% over a range of up to 20 μTorr, depending on operating point). Plasma plume properties, particularly of ions exiting the side of the thruster, were found to be highly sensitive to pressure and may require pressures of less than a few μTorr for accurate measurements. The thruster was found to operate identically with changing beam dump bias voltage to within measurement uncertainties.

Electric propulsion↗
NASA NTRSDate not supplied

Testing the Effectiveness of Integrated Plume Shield for a Hall Thruster

Hall thrusters have been shown to exhibit side plumes with varying degree of erosive power. This article presents the concept of the integrated plume shield for the purpose of mitigating the erosive power of said side plume. A test was conducted on a low-power Hall thruster with and without integrated plume shield and the effect on thruster performance and plume characteristics were measured. Collected data shows that the thruster performed identically to within uncertainty in terms of thrust, specific impulse, and discharge oscillation characteristics. Plume measurements showed up to a 48% reduction in ion current density when averaging over 80° to 105° from the firing axis. A brief analytical study was performed to determine the advantages and disadvantages of using integrated plume shield as opposed to using spacecraft surface covering and placing thrusters on booms. The integrated plume shield was found to provide varying level of advantages in mass, design restrictions, and complexity, which are likely to lead to major cost savings in the long term.

Electric Propulsion↗
NASA NTRSDate not supplied

Extraction of Thruster Plume Ion Population Trends From Retarding Potential Analyzer Data

Characterization of ion plume impingement effects on spacecraft surfaces requires knowledge of the ion energy distributions in the thruster plume. Retarding potential analyzers are a convenient diagnostic that provide measurements of the ion voltage distributions. This work presents an attempt to extract additional information via fitting multiple Maxwellian distributions to the diagnostic traces. Tracking the trends of the fitted ion populations across varying facility pressure, angular location, and thruster operating conditions offers further insight into the makeup of the plume plasma and the behavior of the ion energies as a function of those parameters. This approach provides supporting evidence in establishing margins and building further confidence in the plume modeling validation process.

John T. Yim↗