‡The plume diagnostics and erosion measurement results of the NASA Evolutionary Xenon Thruster (NEXT) 2000 h wear test are presented. This test was conducted with a 40 cm diameter engineering model ion engine, designated EM1, at a 3.52 A beam current and a 1800 V beam power supply voltage. Performance tests, which were conducted over the throttle table range of 1.1-6.9 kW throughout the wear test, demonstrated that EM1 satisfied all thruster performance requirements. The ion engine accumulated 2038 hours of operation at a thruster input power of 6.9 kW, processing 43 kg of xenon. Circular planar probes sweeps measured the ion beam current density at different axial and radial locations from the NEXT engine ion optics’ surface. Beam current density profiles did not change significantly during the wear test. Peak beam current density was 3.97 mA/cm 2 at full power 45 mm downstream of the ion optics. Over the course of the test, the beam flatness parameter was 0.61 at 1.07 kW and 0.71 at 6.85 kW. Plasma properties were also measured at different thruster operating conditions. Post-test CCD imaging of the discharge and neutralizer cathode assemblies indicated that, within the accuracy of the measurement, the discharge and neutralizer keeper and cathode orifice diameters did not change. Post-test laser profilometer surface mappings of the discharge and neutralizer downstream surfaces indicated that 17% of the discharge keeper and < 1% of the neutralizer keeper thicknesses had been eroded at the worst case locations. Results of the CCD imaging of the center and six surrounding accelerator grid apertures indicated that, within the accuracy of the measurement, the apertures’ diameters did not change. Laser profilometer mappings of the downstream surface of the accelerator grid at three ion optics’ radial locations: center, ¼-radius, and ½-radius indicated that the largest pit depth occurred around the center aperture and was 12% of the accelerator grid thickness, whereas, the largest groove depth occurred around the ¼-radius aperture and was 6% of the accelerator grid thickness.
[1]
Michael J. Patterson,et al.
PERFORMANCE EVALUATION OF 40 CM ION OPTICS FOR THE NEXT ION ENGINE
,
2002
.
[2]
John R. Anderson,et al.
Performance of the NSTAR ion propulsion system on the Deep Space One mission
,
2001
.
[3]
Michael J. Patterson,et al.
Status of the NEXT Ion Engine Wear Test
,
2003
.
[4]
Roger M. Myers,et al.
A 100 Hour Wear Test of the NASA NSTAR Ion Thruster
,
1996
.
[5]
Michael J. Patterson,et al.
NEXT: NASA's Evolutionary Xenon Thruster
,
2002
.
[6]
Michael J. Patterson,et al.
Performance of titanium optics on a NASA 30 cm ion thruster
,
2000
.
[7]
R. Cole,et al.
Factors in the electrostatic equilibration between a plasma thrust beam and the ambient space plasma
,
1970
.
[8]
Michael J. Patterson,et al.
Power console development for NASA's electric propulsion outreach program
,
1993
.
[9]
John R. Anderson,et al.
Results of an On-Going Long Duration Ground Test of the DS1 Flight Spare Engine
,
1999
.
[10]
R. Baragiola,et al.
Ion-induced electron emission from clean metals
,
1979
.
[11]
M. Carruth.
A review of studies on ion thruster beam and charge-exchange plasmas
,
1982
.
[12]
Michael J. Patterson,et al.
Design and fabrication of a flight model 2.3 kW ion thruster for the Deep Space 1 Mission
,
1998
.
[13]
M. Patterson,et al.
Plume and Discharge Plasma Measurements of an NSTAR-type Ion Thruster
,
2000
.
[14]
Michael J. Patterson,et al.
Space Station Cathode Design, Performance, and Operating Specifications
,
1998
.
[15]
John R. Anderson,et al.
An overview of the results from an 8200 hour wear test of the NSTAR ion thruster
,
1999
.
[16]
Michael J. Patterson,et al.
Next: NASA's Evolutionary Xenon Thruster development status
,
2003
.
[17]
Michael J. Patterson,et al.
NEXT Ion Engine 2000 Hour Wear Test Results
,
2004
.
[18]
James E. Polk,et al.
In-flight performance of the NSTAR ion propulsion system on the Deep Space One mission
,
2000,
2000 IEEE Aerospace Conference. Proceedings (Cat. No.00TH8484).