NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test Results

• Published in: Journal of propulsion and power 2012-05, Vol.28 (3), p.625-635
• Main Authors: Herman, Daniel A, Soulas, George C, Van Noord, Jonathan L, Patterson, Michael J
• Format: Article
• Language: English
• Subjects: Evolutionary; Failure; Ion thrusters; NASA; Propellants; Solar electric propulsion; Thrusters; Xenon
• ISSN: 0748-4658; 1533-3876
• DOI: 10.2514/1.B34321

NASA's Evolutionary Xenon Thruster program is developing the next-generation solar-electric ion propulsion system to provide future NASA science missions with enhanced in-space propulsion capabilities. As part of a comprehensive thruster service life assessment using both testing and analyses, a long-duration test was initiated in June 2005 to verify the thruster service life modeling and to demonstrate the thruster propellant throughput capability. In July 2010, the NASA's Evolutionary Xenon Thruster long-duration test surpassed 30,352 h of operation, processed more than 495 kg of xenon propellant, and demonstrated greater than 18.2MN s18.2MN·s total impulse. The purpose of this paper is to provide an overview of NASA's Evolutionary Xenon Thruster long-duration test results up to 30,352 h of operation, when it surpassed the NASA Solar Electric Propulsion Technology Application Readiness ion thruster total hours demonstrated. Discussion will include the demonstrated metrics, thruster performance, and observed component erosion. NASA's Evolutionary Xenon Thruster has set records for total hours of operation, total propellant throughput processed, and total impulse demonstrated for any ion or Hall thruster. NASA's Evolutionary Xenon Thruster design improvements have successfully mitigated several ion thruster lifetime-limiting mechanisms, including the first failure mode of the NASA Solar Electric Propulsion Technology Application Readiness ion thruster, namely, failure to prevent electron backstreaming. Thruster performance has been steady with negligible degradation throughout the test. Measured thruster component erosion rates compare favorably to pretest predictions verifying thruster service models. Assuming full-power operation for the remainder of the test, thruster life models and extrapolated erosion measurements both predict penetration of the accelerator grid grooves after greater than 45,000 h of operation and processing more than 800 kg of xenon propellant. Groove penetration is not a failure mechanism in and of itself, but it anticipates thruster failure due to degradation of the accelerator grid structural integrity. [PUBLISHER ABSTRACT]