Results of the mission profile life test

Bechtel, R. T.; Trump, G. E.; James, E. L.

doi:10.2514/6.1982-1905

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…Life test data obtained with the J-series mercury engines indicated a possible small decrease in propellant efficiency with run time. 12 The present control algorithm would maintain the propellant efficiency constant in the face of the engine wear, and the change in engine performance would manifest itself as an increase in eV/ion. This may be preferable on a spacecraft with a finite supply of propellant.…”

Section: Performance Curvementioning

confidence: 99%

Computer-controlled xenon ion engine operation

Brophy

1989

Journal of Propulsion and Power

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The development and testing of a computer control system for a 5-kW xenon ion engine is described. The computer system controls all aspects of the engine operation including startup, steady-state operation, throttling and shutdown of the engine and neutralizer, as well as operation of the valves in the propellant storage and distribution system. The most important engine control algorithms are described. These control algorithms provide flexibility in the operation and throttling of ion engines that has never before been possible. This flexibility is made possible in large part through the use of flow controllers that maintain the total flow rate of propellant into the engine at the proper level. Data demonstrating the throttle capabilities of the engine and control system are presented.

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Section: Performance Curvementioning

confidence: 99%

Computer-controlled xenon ion engine operation

Brophy

1989

Journal of Propulsion and Power

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“…This thruster had previouslybeen operated with mercury for about 820 hr in endurance tests (thrusterJ2 in ref. 8). The thruster was mod|fled, as described in reference12, for use with xenon.…”

Section: Apparatus Thrustermentioning

confidence: 99%

“…Significant endurance test data existfor mercuryIon thrusters with diameters between5 and 30 cm (refs.4 to 8) and powerlevelsup to about3 kW (ref. 8). Predictive analyseshave been generated (refs.9 to 11),but require information suchas valuesof plasmapotential and sputtering yleldnear threshold energies.…”

Section: Introductionmentioning

confidence: 99%

Internal erosion rates of a 10-kW xenon ion thruster

Rawlin

1988

24th Joint Propulsion Conference

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SUMMARYA 30 cm diameterdivergent magneticfieldion thruster, developed for mercuryoperation at 2.7 kN, was modifiedand operatedwith xenonpropellant at a powerlevelof lO kH for 567 hr to evaluatethrusterperformance and lifetime. The majordifferences betweenthis thrusterand its baselineconfiguration were elimination of the threemercuryvaporizers, use of a maln discharge cathode witha largerorifice,reduction In discharge bafflediameter, and use of an Ion accelerating systemwith largeraccelerator grid holes. At a xenonion beamcurrentof 5 A the engineproduceda thrustof 0.33 N at a specific Impulseof 4220 sec and an efficiency of 6B percent. Therewas no measurable _r screengrid erosion. However,grid thickness measurement uncertainties, com-,,', binedwlthestimates of the effectsof reactiveresidualfacilitybackground gasesgavea minimumscreengrid lifetime of 7000 hr. Discharge cathodeorificeerosionrateswere measuredwith threedifferent cathodeswith different initialorificediameters.As the initialorificediameter was Increased from thatof the baselinevalue,the erosionrate decreased to near zero_ Threepotential problemswere identified duringthe wear test. Flrst,the upstream sideof the discharge baffleerodedat an unacceptable rate,nearly two ordersof magnitude greaterthanthat of the baselinemercurythruster. Second,two of the main cathodetubesexperienced oxidation, deformation, and failureafter227 and 243 hr of thruster operation.Thesefailuresare believed to be relatedto the cathodestartingtechnique.Third,the accelerator gridimpingement currentwas more than an orderof magnitude higherthan thatof the baseline mercurythruster, implyinga greatererosionrate. The impingement currentincreaseis primarily due to a greaterchargeexchangeIon currentresulting from the higherbeam current; operation at a higherneutral atom lossrate and; to a lesserextent,the higherfacilitypressure.. The chargeexchangeion erosionwas not quantified in this test. Therewere no measurable changesin the accelerator grid thickness or the accelerator grid ho]ediameters. INTRODUCTIONInertgas ion thrustersystemsare beingconsidered for primarypropulsion for near-Earth, cislunar, and interplanetary missions(refs.I to 3). To reducethe specific mass and complexity of ion propulsion systems,it is deslrableto increase the thrustproducedby each thruster. Thls can be accomplished by increasing the ion beam current(propellant flow rate)and/orthe beam voltage (propellant velocity).Increasing the beam voltageincreases the thrust and specificimpulse, but, It also reducesthe ratioof outputthrustto input power. Therefore, it is oftendesirable to increasethe ion beam curr,_nt as muchas possiblewith minimalincreases in the beam voltage. However,unless changesin otheroperating conditions can be made to offsetthe increased beam This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

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“…From the mission profile life tests, it was observed that the major life-limiting mechanism is the formation of flakes of sputtered material which might be of sufficient size to cause electrical shorts or arcing in the discharge chamber [2]. The internal surfaces of the discharge chamber where the erosion is most severe are subjected to bombardment by ions having energies less than 100 eV, assuming that up to triply charged ions exist in the plasma potential of 32 V within the discharge chamber where the ions are generated.…”

Section: Introductionmentioning

confidence: 99%

Low-energy sputtering of cobalt by cesium ions

Ray

Mukherjee

Handoo

1989

Nuclear Instruments and Methods in Physics Research Section B:

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An experimental facility to investigate low energy (_:500 eV) sputtering of metal surfaces with ions produced by an ion gun is described. Results are reported on the sputtering yield of cobalt by cesium ions in the 100 to 500 eV energy range at a pressure of i x 10 "6Torr. The target was electroplated on a copper substrate. The sputtered atoms were collected_on a cobalt foil surrounding the target. STCo was used as a tracer to determine the sputtering yield._ _ i

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Results of the mission profile life test

Cited by 10 publications

References 6 publications

Computer-controlled xenon ion engine operation

Computer-controlled xenon ion engine operation

Internal erosion rates of a 10-kW xenon ion thruster

Low-energy sputtering of cobalt by cesium ions

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