Single-String Integration Test Measurements of the NEXT Ion Engine Plume

Abstract

Measurements were made of a 40 cm ion-thruster plume as part of the single-string-integration-test (SSIT) activity of Phase I of the NASA's Evolutionary Xenon Thruster (NEXT) project. The NEXT ion engine incorporates design improvements that extend NSTAR power levels and efficiencies. During SSIT, an engineering model (EM2) 40 cm engine was operated using an advanced xenon propellant system in combination with either a GRC power console or advanced power processing unit. Integral goals of the single-string phase were to characterize engine performance over the full input power range and to detail thruster operation within the specification of the NEXT throttle table. Plume diagnostics measurements of relative Xe + and Xe ++ currents were made using near-field and far-field ExB probes. Planar geometry faraday probes were used to obtain beam current density profiles. This paper reports on the characterization of the EM2 plume over a range of SSIT operating conditions, first with the advanced propellant management system teamed with the GRC power console and then with the power-processing unit. I. IntroductionThe need for advanced ion propulsion system capabilities has been demonstrated through in-space propulsion technology assessment analyses conducted by NASA. A higher power, higher throughput capability 25 kW ion propulsion system targeted for robotic exploration of the outer planets was identified as an enabling technology. This power level is an order of magnitude greater than that used on the Deep-Space 1 spacecraft 1 developed and flown under the NASA Solar Electric Propulsion Technology Applications Readiness (NSTAR) program.The NASA Headquarters Office of Space Science, Solar System Exploration Division, selected Glenn Research Center (GRC) to develop NASA's Evolutionary Xenon Thruster (NEXT) under the Next Generation Ion (NGI) Thruster Technology NASA Research Announcement. The NEXT team is composed of NASA GRC, the Jet Propulsion Laboratory (JPL), Aerojet Redmond Rocket Center, and Boeing Electron Dynamic Devices (BEDD), with significant participation by the Applied Physics Laboratory, University of Michigan (UM) and Colorado State University (CSU).The Next Generation Electric Propulsion (NGEP) Project, managed by the NASA Marshall Space Flight Center, is a technology development project within the In-Space Propulsion Technology Program. The primary objective of NGI is to significantly increase performance for primary propulsion to planetary bodies by leveraging NASA's ion propulsion program for low thrust applications. The NEXT system is targeted for robotic exploration of the outer planets using 25kW-class solar-powered electric propulsion. The team will develop thruster, advanced power processing, xenon propellant management and gimbal technologies that will advance the ion propulsion state-of-art to meet the needs of such missions. 2 Component performance was demonstrated over a one-year duration of NEXT phase I, which was completed in August 2003. These components included engineering model...

Multi-Axis Plasma Profiling System for Characterization of Plasma Thruster Plumes

“…1,2 In an ideal beam, ions would exit uniformly across the face of an ion or plasma source, however, due to imperfect plasma production and extraction as well as processes that occur within the beam plasma such as charge exchange and scattering, a real ion beam displays complexly varying current density behavior as a function of position. Current density, along with ion energy, plays a major role in determining the effects of an ion beam when (1) it is directed onto the surface of a material and (2) in applications requiring fine control of thrust. Because of this, it is useful to measure and understand how current density varies at locations downstream of an ion or plasma source.…”