Status of the NEXT Ion Thruster Long-Duration Test after 10,100 h and 207 kg Demonstrated

Herman, Daniel A.; Soulas, George C.; Patterson, Michael J.

doi:10.2514/6.2007-5272

Cited by 22 publications

(27 citation statements)

References 7 publications

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“…Both the NEXT 2000 hour test after 43 kg of propellant throughput and the NEXT LDT after 207 kg of xenon throughput and 10,100 hours of operation have shown no significant change in the electron backstreaming limit. 15,17 Due to the inability of the codes to accurately predict the change in electron backstreaming limit, the best indicators are the current wear tests. These tests indicate that failure from backstreaming electrons due to barrel erosion will not occur prior to any structural failure of the accelerator grid at the peak power throttle point.…”

Section: Barrel Erosion Resulting In Electron Backstreamingmentioning

confidence: 99%

“…17 To date, no neutralizer orifice clogging has been witnessed during the NEXT LDT. 15 The NEXT neutralizer orifice diameter is almost twice as large as the NSTAR neutralizer orifice and higher emission currents are experienced. Both of these factors should minimize the likelihood of neutralizer clogging.…”

Section: Neutralizer Orifice Clogging and Orifice Plate Wearmentioning

confidence: 99%

“…17 Based on the latest in situ measurements during the NEXT LDT, the groove is predicted to penetrate the grid's thickness between 700 to 800 kgs of propellant throughput at the peak operating power. 15 …”

Section: Structural Failure From Downstream Erosion 2000 Hour Wear Tementioning

confidence: 99%

“…5 As of 207 kg xenon throughput and 10,100 hours of operation during the NEXT LDT, the orifice and the cathode orifice plate have shown no measurable wear. 15 This indicates that the cathode orifice plate is sufficiently protected by the graphite keeper for at least 2000 kg of thruster propellant throughput and should have a lifetime many times the qualification requirement.…”

Section: Cathode Orifice Plate Wear/keeper Shortingmentioning

confidence: 99%

“…15,16 The intent of this test is to validate and qualify the NEXT propellant throughput capability at the highest power throttling point to a qualification-level of 450 kg. The operation to date has been at a beam power supply voltage of 1800 V and a beam current of 3.52 A.…”

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confidence: 99%

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Lifetime Assessment of the NEXT Ion Thruster

VanNoord

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Ion thrusters are low thrust, high specific impulse devices with required operational lifetimes on the order of 10,000-100,000 hours. The NEXT ion thruster is the latest generation of ion thrusters under development. The NEXT ion thruster currently has a qualification level propellant throughput requirement of 450 kg of xenon, which corresponds to roughly 22,000 hours of operation at the highest throttling point. Currently, a NEXT engineering model ion thruster with prototype model ion optics is undergoing a long duration test to determine wear characteristics and establish propellant throughput capability. The NEXT thruster includes many improvements over previous generations of ion thrusters, but two of its component improvements have a larger effect on thruster lifetime. These include the ion optics with tighter tolerances, a masked region and better gap control, and the discharge cathode keeper material change to graphite. Data from the NEXT 2000 hour wear test, the NEXT long duration test, and further analysis is used to determine the expected lifetime of the NEXT ion thruster. This paper will review the predictions for all of the anticipated failure mechanisms. The mechanisms will include wear of the ion optics and cathode's orifice plate and keeper from the plasma, depletion of low work function material in each cathode's insert, and spalling of material in the discharge chamber leading to arcing. Based on the analysis of the NEXT ion thruster, the first failure mode for operation above a specific impulse of 2000 s is expected to be the structural failure of the ion optics at 750 kg of propellant throughput, 1.7 times the qualification requirement. An assessment based on mission analyses for operation below a specific impulse of 2000 s indicates that the NEXT thruster is capable of double the propellant throughput required by these missions.

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Section: Barrel Erosion Resulting In Electron Backstreamingmentioning

confidence: 99%

Section: Neutralizer Orifice Clogging and Orifice Plate Wearmentioning

confidence: 99%

Section: Structural Failure From Downstream Erosion 2000 Hour Wear Tementioning

confidence: 99%

Section: Cathode Orifice Plate Wear/keeper Shortingmentioning

confidence: 99%

mentioning

confidence: 99%

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Lifetime Assessment of the NEXT Ion Thruster

VanNoord

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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An Overview of Recent Developments in Electric Propulsion for NASA Science Missions

Pencil

2008

2008 IEEE Aerospace Conference

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The primary source of electric propulsion development throughout NASA is managed by the In-Space Propulsion Technology Project at the NASA Glenn Research Center for the Science Mission Directorate. The objective of the Electric Propulsion project area is to develop near-term electric propulsion technology to enhance or enable science mission while minimizing risk and cost to the end user. Major hardware tasks include developing NASA's Evolutionary Xenon Thruster (NEXT), developing a long-life High Voltage Hall Accelerator (HIVHAC), developing an advanced feed system, and developing cross-platform components. The objective of the NEXT task is to advance next generation ion propulsion technology readiness. The NEXT system consists of a highperformance, 7-kW ion thruster; a high-efficiency, 7-kW power processor unit (PPU); a highly flexible advanced xenon propellant management system (PMS); a lightweight engine gimbal; and key elements of a digital control interface unit (DCIU) including software algorithms. This design approach was selected to provide future NASA science missions with the greatest value in mission performance benefit at a low total development cost. The objective of the HIVHAC task is to advance the Hall thruster technology readiness for science mission applications. The task seeks to increase specific impulse, throttle-ability and lifetime to make Hall propulsion systems applicable to deep space science missions. The primary application focus for the resulting Hall propulsion system would be cost-capped missions, such as competitivelyselected, Discovery-class missions. The objective of the advanced xenon feed system task is to demonstrate novel manufacturing techniques that will significantly reduce mass, volume, and footprint size of xenon feed systems over conventional feed systems. The task has focused on the development of a flow control module, which consists of a three-channel flow system based on a piezo-electrically actuated valve concept. Component standardization and simplification are being investigated through the Standard Architecture task to reduce first user costs for implementing electric propulsion systems. Progress on current hardware development, recent test activities and future plans are discussed.' 2

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Recent electric propulsion development activities for NASA science missions

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2009

2009 IEEE Aerospace Conference

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Abstract(The primary source of electric propulsion development throughout NASA is managed by the In-Space Propulsion Technology Project at the NASA Glenn Research Center for the Science Mission Directorate. The objective of the Electric Propulsion project area is to develop near-term electric propulsion technology to enhance or enable science missions while minimizing risk and cost to the end user. Major hardware tasks include developing NASA's Evolutionary Xenon Thruster (NEXT), developing a long-life High Voltage Hall Accelerator (HIVHAC), developing an advanced feed system, and developing crossplatform components. The objective of the NEXT task is to advance next generation ion propulsion technology readiness. The baseline NEXT system consists of a highperformance, 7-kW ion thruster; a high-efficiency, 7-kW power processor unit (PPU); a highly flexible advanced xenon propellant management system (PMS); a lightweight engine gimbal; and key elements of a digital control interface unit (DCIU) including software algorithms. This design approach was selected to provide future NASA science missions with the greatest value in mission performance benefit at a low total development cost. The objective of the HIVHAC task is to advance the Hall thruster technology readiness for science mission applications. The task seeks to increase specific impulse, throttle-ability and lifetime to make Hall propulsion systems applicable to deep space science missions. The primary application focus for the resulting Hall propulsion system would be cost-capped missions, such as competitivelyselected, Discovery-class missions. The objective of the advanced xenon feed system task is to demonstrate novel manufacturing techniques that will significantly reduce mass, volume, and footprint size of xenon feed systems over conventional feed systems. This task has focused on the development of a flow control module, which consists of a three-channel flow system based on a piezo-electrically actuated valve concept, as well as a pressure control module, which will regulate pressure from the propellant tank. Cross-platform component standardization and simplification are being investigated through the Standard Architecture task to reduce first user costs for implementing electric propulsion systems. Progress on current hardware development, recent test activities and future plans are discussed.

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Status of the NEXT Ion Thruster Long-Duration Test after 10,100 h and 207 kg Demonstrated

Cited by 22 publications

References 7 publications

Lifetime Assessment of the NEXT Ion Thruster

Lifetime Assessment of the NEXT Ion Thruster

An Overview of Recent Developments in Electric Propulsion for NASA Science Missions

Recent electric propulsion development activities for NASA science missions

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