NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test as of 736 kg of Propellant Throughput

Abstract

The NASA's Evolutionary Xenon Thruster (NEXT) program is developing the next-generation solar-electric ion propulsion system with significant enhancements beyond the state-of-the-art NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) ion propulsion system to provide future NASA science missions with enhanced mission capabilities. A Long-Duration Test (LDT) was initiated in June 2005 to validate the thruster service life modeling and to qualify the thruster propellant throughput capability. The thruster has set electric propulsion records for the longest operating duration, highest propellant throughput, and most total impulse demonstrated. At the time of this publication, the NEXT LDT has surpassed 42,100 h of operation, processed more than 736 kg of xenon propellant, and demonstrated greater than 28.1 MN•s total impulse.Thruster performance has been steady with negligible degradation. The NEXT thruster design has mitigated several lifetime limiting mechanisms encountered in the NSTAR design, including the NSTAR first failure mode, thereby drastically improving thruster capabilities. Component erosion rates and the progression of the predicted life-limiting erosion mechanism for the thruster compare favorably to pretest predictions based upon semi-empirical ion thruster models used in the thruster service life assessment. Service life model validation has been accomplished by the NEXT LDT. Assuming full-power operation until test article failure, the models and extrapolated erosion data predict penetration of the accelerator grid grooves after more than 45,000 hours of operation while processing over 800 kg of xenon propellant. Thruster failure due to degradation of the accelerator grid structural integrity is expected after groove penetration.

Development and Testing of High Current Hollow Cathodes for High Power Hall Thrusters

“…More specifically, NASA GRC-developed HCAs have demonstrated in excess of 42,000 hours of operation during the NASA Evolutionary Xenon Thruster (NEXT) long duration test (LDT). 12 In the NEXT LDT, two HCAs are employed, and they include a discharge cathode assembly (DCA) and a neutralizer cathode assembly (NCA). The DCA operates at emission currents < 20 A and the NCA operates at emission currents ≤ 6.5 A.…”

Architecture for in-space robotic assembly of a modular space telescope

“…As a quantitative example, the sunshade spacecraft with a 200 second specific impulse thruster would consume 1270 kg∕year of fuel to compensate for SRP. Using the NASA Evolutionary Xenon Thruster (NEXT) with a 4170 second specific impulse 77 would consume 61 kg∕year. For the much smaller (area) metrology spacecraft, the SRP compensation would consume 22 and 1 kg∕year for the chemical propulsion system and NEXT ion thruster, respectively.…”

Status of propulsion technology development under the NASA In-Space Propulsion Technology program

“…5 The NEXT LDT life test demonstrated the largest total impulse, highest propellant throughput, and longest operating duration of any electric propulsion thruster in the history of space propulsion. 6 A collaborative test program with The Aerospace Corporation (TAC) in El Segundo, CA examines the plume, particle, and field environments of the NEXT thruster. A series of measurements was completed to verify basic characteristics of NEXT operation, and expand on the available public-domain and internal databases regarding NASA technology and its potential use on non-NASA spacecraft systems.…”