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  • 1
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    Uncertainty in Inverted Pendulum Thrust Measurements (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: An uncertainty analysis of a common configuration of electric propulsion thrust stand is presented. The analysis applies to inverted pendulum thrust stands operating in a null-coil configuration with in-situ calibration. Several sources of bias and precision uncertainty are discussed, propagated, and combined to form conservative estimates of the relative and absolute thrust uncertainties. A case study of the NASA Glenn Research Center Vacuum Facility 6 thrust stand is presented. For the thruster investigated, the uncertainty was estimated to be 6.9mN over the entire span of thrust. This uncertainty represents a maximum instrument bias introduced by the thrust stand. The paper does not address repeatability of actual thrust measurements, as this is generally beyond the influence of the thrust stand and can be dependent on a large number of factors.
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN59049 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Update on the Nested Hall Thruster Subsystem for the NextSTEP XR-100 Program (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Under the NextSTEP program led by Aerojet Rocketdyne in collaboration with NASA Glenn Research Center the University of Michigan, and the Jet Propulsion Laboratory, the XR-100 100 kW Electric Propulsion system is being developed to Technology Readiness Level (TRL) 5. As part of this program, the X3, a Nested Hall Thruster (NHT) designed to operate at powers up to 200kW, is being further developed through parallel modeling and experimental efforts with the ultimate goal of supporting a 100kW-100hr system test in the final year of the NextSTEP program. Recent developments for the X3 subsystem are presented including a summary of testing and modeling results and design updates in anticipation of a risk reduction test scheduled for the summer of 2018.
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN58707 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH
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    NASA TECHNICAL REPORTS
  • 3
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    Update on the Nested Hall Thruster Subsystem for the NextSTEP XR-100 Program (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Under the NextSTEP program led by Aerojet Rocketdyne in collaboration with NASA Glenn Research Center the University of Michigan, and the Jet Propulsion Laboratory, the XR-100 100 kW Electric Propulsion system is being developed to Technology Readiness Level (TRL) 5. As part of this program, the X3, a Nested Hall Thruster (NHT) designed to operate at powers up to 200kW, is being further developed through parallel modeling and experimental efforts with the ultimate goal of supporting a 100kW-100hr system test in the final year of the NextSTEP program. Recent developments for the X3 subsystem are presented including a summary of testing and modeling results and design updates in anticipation of a risk reduction test scheduled for the summer of 2018.
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN57834 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
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    NASA TECHNICAL REPORTS
  • 4
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    Preparation for Hollow Cathode Testing for the Advanced Electric Propulsion System at NASA Glenn Research Center (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA Glenn Research Center is performing activities to support the unique needs of hollow cathode development and testing for the Advanced Electric Propulsion System (AEPS). Three existing vacuum facilities have been outfitted as cathode test facilities, and each will serve a different role in upcoming testing. Vacuum Facility 67 is being developed to serve as a long-duration test facility for the Engineering Development Unit cathode, which is to be delivered by the AEPS contractor. It will feature a thruster-like magnetic field simulator and cold-cycle capability via a liquid nitrogen-cooled cold plate. Vacuum Facility 17 is being developed as a test facility for short- to medium-duration experiments in order to provide auxiliary support for the long-duration testing. It will feature a magnetic field simulator but not cold-cycling. Finally, Vacuum Facility 1 will be a high-pumping speed cathode development environment, and will feature an array of plasma and temperature diagnostics. In addition to the facility preparation work, a new cathode, referred to as the Mark II, has been designed. The Mark II is an evolution of the Technology Demonstration Unit cathodes that better evokes the geometry, fabrication, and construction of the forthcoming Engineering Development Unit. This cathode serves as a transition between the Technology Demonstration Unit cathodes used during early thruster development and the forthcoming Engineering Development Unit cathodes. It will be used as a means of verifying the new test facilities prior to arrival of Engineering Development Unit hardware. Details of the Mark II design and key features are presented, as well as details of future work to be performed.
    Keywords: Spacecraft Propulsion and Power
    Type: AIAA-2018-4425 , NASA/TM-2018-219954 , GRC-E-DAA-TN59236 , 2018 Joint Propulsion Conference; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
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  • 5
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    High-Power Performance of a 100-kW Class Nested Hall Thruster (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Operations of a three-channel 100-kW class nested Hall thruster at total power levels from 5 to 102 kW and discharge currents from 16 to 247 A were successful. The thruster was operated in all seven available channel combinations at discharge voltages of 300, 400, and 500 V and at current densities that were 0.60 and 0.95 of the nominal value. Additional test points were also collected at 1.20 the nominal current density. The thruster was throttled through a total of forty-six unique operating conditions. At each condition, thruster performance was measured using a high-power thrust stand designed to measure up to 8 N of thrust. From these thrust measurements, specific impulse and efficiency were calculated. All seven channel combinations showed similar performance at a given discharge voltage and current density. The largest thrust recorded was 5.42 N at 99 kW, 400 V discharge voltage. Total efficiency values 0.54 to 0.67, and total specific impulse ranged from 1800 seconds to 2650 seconds. Discharge current oscillations were also measured. Generally these oscillations increased on the inner and middle channels during multi-channel mode but stayed roughly a constant fraction of the channel discharge current for the outer channel in both single- and multi-channel operation. We also found that the thrust of the three channels firing together was not significantly higher than the sum of each channel _ring individually, a result that differs from what was found previously for nested Hall thrusters.
    Keywords: General; Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN47556 , International Electric Propulsion Conference (IEPC); Oct 08, 2017 - Oct 12, 2017; Atlanta, GA; United States
    Format: application/pdf
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  • 6
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    Characterization of Propellant Flow and Bias Required to Initiate an Arc Discharge in a Heaterless Hollow Cathode (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Heaterless hollow cathodes provide an opportunity to reduce complexity and improve reliability in electric propulsion systems. While removal of the heater has little effect on steady-state operation of a hollow cathode, it has a considerable effect on the ignition process. To successfully integrate a heaterless hollow cathode into a spaceflight electric propulsion system, it will be necessary to establish definitive requirements for the propellant feed and electrical subsystems so that ignition of a plasma discharge can be achieved reliably. The aim of this research was to form a better understanding of these requirements by performing an investigation of the propellant flow and voltage conditions required for the ignition of a plasma arc discharge. This aim was achieved by performing discharge initiation experiments using both a specially designed experimental apparatus and a functional heaterless hollow cathode assembly. It was demonstrated that there is a distinct difference in the voltage required to initiate a plasma discharge between two common electric propulsion propellants, xenon and krypton, which suggests that the developmental testing of heaterless hollow cathodes needs to be performed with the appropriate propellant gas species. Heaterless hollow cathode ignition experiments showed that the keeper orifice diameter has a strong effect on the voltage required to ignite a plasma discharge at a given propellant mass flow rate, while the effect of keeper-cathode separation distance was only strong at flow rates below 25 sccm (Xe).
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN70748 , AIAA Joint Propulsion Conference 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    NASA TECHNICAL REPORTS
  • 7
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    High Power Demonstration of a 100 kW Nested Hall Thruster System (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The XR-100 team successfully completed high power system testing of a Nested Hall Thruster system made up of the X3 Nested Hall Thruster, a modular Power Processing Unit, and a 5 valve Mass Flow Controller as the culmination of work performed under a NASA NextSTEP program. The test campaign attained several key firsts, including highest directly measured thrust of an electric propulsion (EP) string, highest demonstrated current of an EP string, and highest power operation of an EP string at thermal equilibrium published to date. Most importantly, the XR-100 system testing demonstrated that a 100 kW-class Nested Hall Thruster system has comparable performance and behavior to current state-of-the-art mid power Hall Thrusters, validating that the heritage technology can be scaled up to 100+ kW
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN71159 , AIAA Joint Propulsion Conference 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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  • 8
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    High Power Demonstration of a 100 kW Nested Hall Thruster System (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: The XR-100 team successfully completed high power system testing of a Nested Hall Thruster system made up of the X3 Nested Hall Thruster, a modular Power Processing Unit, and a 5 valve Mass Flow Controller as the culmination of work performed under a NASA NextSTEP program. The test campaign attained several key firsts, including highest directly measured thrust of an electric propulsion (EP) string, highest demonstrated current of an EP string, and highest power operation of an EP string at thermal equilibrium published to date. Most importantly, the XR-100 system testing demonstrated that a 100 kW-class Nested Hall Thruster system has comparable performance and behavior to current state-of-the-art mid power Hall Thrusters, validating that the heritage technology can be scaled up to 100+ kW
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN71845 , AIAA Propulsion and Energy Forum and Exposition 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    NASA TECHNICAL REPORTS
  • 9
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    Model for the Increase in Thruster Efficiency from Cross-Channel Coupling in Nested Hall Thrusters (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-02
    Description: Multi-channel operation in nested Hall thrusters has been experimentally shown to enhance thruster efficiency compared to single-channel operation at constant power. This is the result of higher local neutral density due to the flow from adjacent channels, leading to two effects: neutral ingestion and decreased plume divergence. Analytical expressions for the impact of these cross-channel effects on efficiency are derived for a nested Hall thruster based on the flow of neutrals between channels. These expressions are dependent on the geometry and operation of a given thruster, as well as its performance in single-channel operation. The mass utilization efficiency increase from cross-channel neutrals is found to be primarily driven by the distance between adjacent channels. A comparison of the model predictions of efficiency to experiment also shows agreement within uncertainty. These results are discussed in the context of best practices for nested Hall thruster channel testing and optimal thruster design.
    Keywords: Spacecraft Propulsion and Power
    Type: IEPC-2019-204 , GRC-E-DAA-TN72388 , International Electric Propulsion Conference; Sep 15, 2019 - Sep 20, 2019; Vienna; Australia
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  • 10
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    Preparation for Hollow Cathode Testing for the Advanced Electric Propulsion System at NASA Glenn Research Center (2018)
    In:  CASI
    Details
    Publication Date: 2019-11-15
    Description: NASA Glenn Research Center is performing activities to support the unique needs of hollow cathode development and testing for the Advanced Electric Propulsion System (AEPS). Three existing vacuum facilities have been outfitted as cathode test facilities, and each will serve a different role in upcoming testing. Vacuum Facility 67 is being developed to serve as a long-duration test facility for the Engineering Development Unit cathode, which is to be delivered by the AEPS contractor. It will feature a thruster-like magnetic field simulator and cold-cycle capability via a liquid nitrogen-cooled cold plate. Vacuum Facility 17 is being developed as a test facility for short- to medium-duration experiments in order to provide auxiliary support for the long-duration testing. It will feature a magnetic field simulator but not cold-cycling. Finally, Vacuum Facility 1 will be a high-pumping speed cathode development environment, and will feature an array of plasma and temperature diagnostics. In addition to the facility preparation work, a new cathode, referred to as the Mark II, has been designed. The Mark II is an evolution of the Technology Demonstration Unit cathodes that better evokes the geometry, fabrication, and construction of the forthcoming Engineering Development Unit. This cathode serves as a transition between the Technology Demonstration Unit cathodes used during early thruster development and the forthcoming Engineering Development Unit cathodes. It will be used as a means of verifying the new test facilities prior to arrival of Engineering Development Unit hardware. Details of the Mark II design and key features are presented, as well as details of future work to be performed.
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN58391 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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