NEXT Ion Engine 2000 Hour Wear Test Plume and Erosion Results

Kamhawi, Hani; Soulas, George C.; Patterson, Michael J.; Frandina, Michael M.

doi:10.2514/6.2004-3792

Cited by 19 publications

(34 citation statements)

References 11 publications

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“…5 indicate that 45 mm downstream from the ion optics, peak current density at the thruster ion beam current of 1.2 A was 1.53 mA/cm 2 which is within 1 percent of the peak current density of 1.54 mA/cm 2 which was measured during the 2000 h wear test. 11 Also, results in fig. 5 indicate that 45 mm downstream from the ion optics, peak current density at the thruster ion beam current of 3.52 A was 3.97 mA/cm 2 which matches the value measured during the 2000 h wear test 11 As both figures demonstrate, the shape functions of the ion current density profiles were similar at all beam currents evaluated.…”

Section: A Near-field Radial Beam Current Density Profilesmentioning

confidence: 99%

“…11 Also, results in fig. 5 indicate that 45 mm downstream from the ion optics, peak current density at the thruster ion beam current of 3.52 A was 3.97 mA/cm 2 which matches the value measured during the 2000 h wear test 11 As both figures demonstrate, the shape functions of the ion current density profiles were similar at all beam currents evaluated. Integration of the radial beam current density profiles (assuming azimuthal symmetry) yielded beam currents that were higher than the measured beam current by as much as 15 percent.…”

Section: A Near-field Radial Beam Current Density Profilesmentioning

confidence: 99%

“…11 Comparing the NEXT and NSTAR flatness parameters indicated that the NEXT EM1 ion engine beam flatness parameters were 45 to 85 percent higher than those of the NSTAR ion engine. 5,12 Higher flatness parameters apparently correspond directly with increased electron backstreaming limits, and are speculated to have contributed to increases in ion optics perveance and screen grid ion transparencies relative to those of the 30 cm ion optics on an NSTAR engine.…”

Section: A Near-field Radial Beam Current Density Profilesmentioning

confidence: 99%

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

Snyder

Kamhawi

Patterson³

et al. 2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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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...

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Section: A Near-field Radial Beam Current Density Profilesmentioning

confidence: 99%

Section: A Near-field Radial Beam Current Density Profilesmentioning

confidence: 99%

Section: A Near-field Radial Beam Current Density Profilesmentioning

confidence: 99%

See 1 more Smart Citation

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

Snyder

Kamhawi

Patterson³

et al. 2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

Self Cite

View full text Add to dashboard Cite

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“…In the 2000 hour wear test of the NEXT ion thruster 6 , a large amount of erosion was observed in the apertures at the edge of the extraction grids compared to the central regions 7 . The erosion was in the form of irregular star patterns in general, and occurred past the 15.1 cm radius point on the grids.…”

Section: Outer Radial Aperture Erosion Studymentioning

confidence: 99%

Progress In NEXT Ion Optics Modeling

Emhoff

Boyd

2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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“…35 It experienced a slight decrease in diameter from sputter material deposition, but the measured decrease was approximately equal to its uncertainty. 36 As long as the orifice plate is protected by the keeper, minimal wear is anticipated. The cathode orifice diameter decreased slightly from deposited materials, but is not expected to change much over the life of the thruster.…”

Section: Cathode Orifice Plate Wear/keeper Shortingmentioning

confidence: 99%

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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NEXT Ion Engine 2000 Hour Wear Test Plume and Erosion Results

Cited by 19 publications

References 11 publications

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

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

Progress In NEXT Ion Optics Modeling

Lifetime Assessment of the NEXT Ion Thruster

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