Hall-Effect Thruster--Cathode Coupling, Part I: Efficiency Improvements from an Extended Outer Pole

Sommerville, Jason D.; King, Lyon B.

doi:10.2514/1.50123

Cited by 34 publications

(36 citation statements)

References 9 publications

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“…Since the discharge current must be conserved across magnetic field lines, if the backpressure is a major contributor to the plume mobility, we would expect as pressure decreases for the electric field to extend further downstream along with higher electron temperature through Joule heating. Indeed, as pressure decreases, studies have shown that the electric field extends further downstream [8,11,15,17,18,38,39]. The reasons for this though however are not clear, since in this region of the plume the contribution of the neutrals to the cross-field electron mobility is very small compared to the effective mobility, which approaches or exceeds the Bohm value [56,57].…”

Section: On Neutral Ingestion and Cathode Position In Hall Thrustmentioning

confidence: 91%

“…Possible examples include: the ingestion of neutrals from the cathode, the creation of currents in the near-field beam that stream radially without producing thrust, charge exchange in the near-field plume, discharge current oscillations, electron mobility in the near-field plume related to cathode coupling, or shifts in the ionization and acceleration zones in the discharge. Among these, a preponderance of evidence now implicates shifts in the spatial distribution of the plasma properties as being important contributors to the apparent level of ingestion [8,11,15,17,18,38,39]. These studies, which have been conducted on unshielded Hall thrusters using externally mounted hollow cathodes, have demonstrated how the backpressure can alter the spatial distribution of the plasma properties and affect the performance.…”

Section: On Neutral Ingestion and Cathode Position In Hall Thrustmentioning

confidence: 97%

“…The other two locations were outside the magnetic circuit of the thruster, referred to as externally mounted configurations, at either the near location of R/R m = 2.64 or the far location at R/R m = 4.90. With both external mounts being outside the separatrix [38,39] of the magnetic circuit where the field is weak, the electrons are not magnetized and their coupling with the discharge is impeded [16,38,39,[58][59][60][61][62][63]. …”

Section: A H6ms Hall Thrustermentioning

confidence: 99%

“…The approach has seemingly worked well in commercial applications, as demonstrated by the hundreds of Hall thrusters operating at 1.5 kW or less that have flown in space since the 1970s [30][31][32][33][34][35][36][37]. Interest in the development of high-power Hall thrusters operating at greater than 10 kW for NASA applications has renewed interest in understanding ground test facility effects at a more fundamental level since finite pressure effects can alter the distribution of plasma properties in the discharge chamber [8,11,15,17,18,38,39]. Besides changing performance, such variations could impact thermal margins, discharge stability, and most critically, lifetime.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, studies of Hall thrusters with internally mounted cathodes have shown this is the most energetically favorable configuration and provides for a high-level of performance primarily through decreased plume divergence and improved cathode coupling [16,38,39,[58][59][60][61][62][63]. Visual observations, shown in Figure 3, also reveal that thrusters with external cathodes are typically surrounded by a "halo" as the electrons collide with background gases causing neutral emission [58].…”

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confidence: 95%

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Finite Pressure Effects in Magnetically Shielded Hall Thrusters

Hofer¹,

Anderson²

2014

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

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We describe the effects of finite pressure in a large vacuum facility on a magnetically shielded Hall thruster using internally and externally mounted cathodes. A numerical model of the pumping system was first used to guide the placement of an ionization gauge and an auxiliary propellant injector used for increasing the backpressure. The laboratory model H6MS Hall thruster was operated at 300 and 800 V discharge voltage, 2-20 A discharge current, and 0.6-9.0 kW discharge power at pressures calibrated for xenon from 2.4 to 100 uTorr-Xe. The hollow cathode was located in three positions: internally mounted on thruster centerline and two external mounts outside of the magnetic circuit. Performance variations exceed that expected from ingestion of background gas in all configurations but were still consistent with prior studies of unshielded Hall thrusters. Magnetic field strength, cathode location, and magnitude of discharge oscillations can greatly affect the apparent level of ingestion, which suggests that mechanisms other than ingestion of background gas affect the pressure sensitivity of the discharge. In particular, cathode location is shown to have a profound influence on the measured performance and stability. When the internally mounted cathode is used, the plasma response is shown to be much less sensitive to pressure changes than when an externally mounted cathode is employed. Our results suggest that high-power Hall thrusters using internally mounted cathodes minimize the effects of finite pressure on performance and stability, providing a path for reliably correlating ground tests with flight performance.

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Section: On Neutral Ingestion and Cathode Position In Hall Thrustmentioning

confidence: 91%

Section: On Neutral Ingestion and Cathode Position In Hall Thrustmentioning

confidence: 97%

Section: A H6ms Hall Thrustermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 95%

See 3 more Smart Citations

Finite Pressure Effects in Magnetically Shielded Hall Thrusters

Hofer¹,

Anderson²

2014

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

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Electrical characteristics of a Hall effect thruster body in a vacuum facility testing environment

et al. 2022

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The operational characteristics of Hall effect thrusters are altered by conductive surfaces in vacuum facilities. Conductive surfaces alter charge distribution in the plume by providing pathways for electron-ion recombination that do not exist in the spaceflight environment. Charge recombination pathways impact thruster performance and plume behavior through mechanisms that are not entirely understood. The incomplete understanding of the relationship between charge recombination pathways and thruster behavior limits the ability to characterize thruster performance through ground testing. This paper quantifies the effect of polarity and magnitude of body-to-cathode voltage on coupling between the thruster body and the local plasma environment. The effort operates the T-140 Hall thruster at a single, fixed operating condition of 300 V, 3.5 kW, with anode and cathode xenon flow rates of 11.6 ± 0.03 mg/s and 1.61 ± 0.12 mg/s, respectively. During data collection, the chamber was maintained at a pressure of 8.7 × 10–6 Torr-Xe. The thruster body-to-ground voltage is manipulated by varying body-to-ground resistance. Results show the thruster pole face and body circumference couple to the local plasma environment through distinct sheaths. The polarity of the body-to-cathode voltage determines the characteristics of these sheaths. Therefore, the body-to-cathode voltage controls the interaction between the thruster body recombination pathway and the local plasma environment.

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Demonstration and experimental characteristics of a water-vapor Hall thruster

et al. 2023

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Water is an attractive candidate for condensable propellants owing to its availability, handleability, and sustainability. This study proposes the use of water vapor as a propellant for a low-power Hall thruster, and experimentally demonstrates the feasibility of this proposal. Based on the performance estimation from the plume diagnostics, a thrust-to-power ratio of 19 mN/kW, specific impulse of 550–860 s, and anode efficiency of 5–8 % were obtained at an anode power of 233–358 W. From further efficiency analysis, the mass utilization efficiency of water was found to be the most deteriorated among the internal efficiencies compared to the conventional xenon propellant, which was consistent with the expectations from a small discharge current oscillation, large beam divergence, and increase in low-energy ions. Moreover, additional power loss via reactions unique to polyatomic molecules was indicated by evaluation of the ionization cost. In this experiment, the mass utilization efficiency was improved with an increase in the anode voltage from 200 to 240 V without degradation of the power utilization. This suggests that operating at a higher voltage is more suitable for a water-vapor Hall thruster.

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Hall-Effect Thruster--Cathode Coupling, Part I: Efficiency Improvements from an Extended Outer Pole

Cited by 34 publications

References 9 publications

Finite Pressure Effects in Magnetically Shielded Hall Thrusters

Finite Pressure Effects in Magnetically Shielded Hall Thrusters

Electrical characteristics of a Hall effect thruster body in a vacuum facility testing environment

Demonstration and experimental characteristics of a water-vapor Hall thruster

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