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™S£"«TjZTl^l 0 ? ? Wor T a,i°n is estimated lo average 1 hour per response, including the time tor reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Recorts (0704-01881 1215 Jefferson Davis H,ghway. Suite 1204. Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no personal besubletTanyZ°t^Z)^1^ Zl collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) TITLE AND SUBTITLE REPORT TYPE Technical Paper AUTHOR(S) PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSORING /MONITORING AGENCY NAME(S) AND ADDRESS(ES)Air Force Research Laboratory (AFMC) AFRL/PRS 5 Pollux Drive Edwards AFB CA 93524-7048 DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited. AbstractThree different types of sub kilowatt class Hall thrusters for on-board propulsion of small to mid size satellites are being developed at Busek. This paper describes their performance focusing on plasma behavior outside of the thrusters end contrasts the typical Hall thruster plasma with that encountered in MHD generators and accelerators researched In the past and familiar to the plasmadynamlc community. A Bimple performance predicting analytical model, applicable to all sizes of thrusters also Is presented. It adequately matches the measured thrust and specific Impulse expressed in terms of primary electron loss parameter, and an overall voltage loss which includes the loss In the plasma bridge between the external cathode and the thruster. The external plasma plume was surveyed using a Faraday cup and an emissive probe to measure the beam current and the plasma potential. These measurements, together with the model support our visual observation that the plume, of a well performing thruster. forms at its center a highly conductive jet with sharply defined cone shaped boundaries. These boundaries were tentatively identified as an ion acoustic shock. The preliminary data and analysis indicate that the plasma downstream of the ion acoustic shock is at least partially responsible for the widely reported correlation between increasing test tank pressure Bnd an increase in performance of Hall thrusters.

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