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Status of the NEXT Long-Duration Test After 23,300 Hours of OperationThe NASA s Evolutionary Xenon Thruster (NEXT) program is developing the next-generation ion propulsion system with significant enhancements beyond the state-of-the-art in ion propulsion to provide future NASA science missions with enhanced mission capabilities at a low total development cost. As part of a comprehensive thruster service life assessment utilizing both testing and analyses, a Long-Duration Test (LDT) was initiated in June 2005, to verify the NEXT propellant throughput capability to a qualification-level of 450 kg, 1.5 times the anticipated throughput requirement of 300 kg per thruster from mission analyses. The LDT is being conducted with a modified, flight-representative NEXT engineering model ion thruster, designated EM3. As of July 2009, the thruster has accumulated 23,300 h of operation with extensive durations at the following input powers: 6.9, 4.7, 1.1, and 0.5 kW. The thruster has processed 427 kg of xenon surpassing the NSTAR propellant throughput demonstrated during the extended life testing of the Deep Space 1 flight spare ion thruster and approaching the NEXT development qualification throughput goal. The NEXT LDT has demonstrated a total impulse of 16.0 10(exp 6) N/s; the highest total impulse ever demonstrated by an ion thruster. Thruster performance tests are conducted periodically over the entire NEXT throttle table with input power ranging 0.5 to 6.9 kW. Thruster performance parameters including thrust, input power, specific impulse, and thruster efficiency have been nominal with little variation to date. The NSTAR first-failure mode, accelerator aperture erosion leading to electron backstreaming, has been mitigated in the NEXT design. The severe NSTAR discharge cathode assembly erosion has been mitigated by a graphite keeper in the NEXT thruster. Tracking of the NEXT first failure mode, charge-exchange ion impingement on the accelerator grid causing hexagonal groove erosion, is consistent with model predictions and indicates thruster life greater than or equal to 750 kg throughput. This paper presents the status, performance data, and wear characteristics of the NEXT LDT to date.
Document ID
20100002893
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Herman, Daniel A. (ASRC Aerospace Corp. Cleveland, OH, United States)
Soulas, George C. (NASA Glenn Research Center Cleveland, OH, United States)
Patterson, Michael J. (NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 25, 2013
Publication Date
December 1, 2009
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
NASA/TM-2009-215837
AIAA Paper 2009-4917
E-17097
Meeting Information
Meeting: 45th Joint Propulsion Conference and Exhibit
Location: Denver, CO
Country: United States
Start Date: August 2, 2009
End Date: August 5, 2009
Sponsors: Society of Automotive Engineers, Inc., American Inst. of Aeronautics and Astronautics, American Society of Mechanical Engineers, American Society for Electrical Engineers
Funding Number(s)
WBS: WBS 346620.04.08.02.02.01
Distribution Limits
Public
Copyright
Public Use Permitted.

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