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Magnetic Nozzle and Plasma Detachment Scenario



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Magnetic Nozzle and Plasma Detachment Scenario Boris Breizman Mikhail Tushentsov and Alex Arefiev Institute for Fusion Studies UT Austin In collaboration with an experimental team R D Bengtson and J Meyers UT Austin D G Chavers C C Dobson and J E Jones MSFC B M Schuettpelz University of Alabama Huntsville C Deline University of Michigan Ann Arbour Research supported in part by Ad Astra Rocket Company November 12 16 2007 Orlando Florida 49th APS DPP Meeting TALK OUTLINE Plasma detachment issue MHD detachment concept and theory motivated by VASIMR project Numerical model for steady state magnetic nozzle Code testing and numerical results Experiment DDEX Marshall Space Flight Center Summary APS DPP 2007 1 PLASMA DETACHMENT PROBLEM Plasma based propulsion systems generate thrust by ejecting directed plasma flow A strong magnetic field is used to guide the plasma The ejected plasma must break free from the spacecraft to produce thrust There are two scenarios for plasma detachment Detachment from the magnetic field by breaking the frozen in constraint via recombination or some other mechanism Detachment with the magnetic field by stretching the field lines along the flow due to plasma plasma current APS DPP 2007 vacuum field lines field lines stretched by the plasma nozzle wall plasma current 2 MHD DETACHMENT CONCEPT 4 Conserved quantities Magnetic flux BS const Flow velocity V const Plasma flux niV S const 3 B 2 8 S 2 2 2 mi nV i 2 1 0 0 6 0 8 1 1 2 1 S 1 4 S S nozzle cross section Magnetic energy decreases downstream faster than plasma kinetic energy An initially sub Alfv nic flow becomes super Alfv nic downstream Plasma flow can stretch the magnetic field lines after B 2 8 drops below mi niV 2 2 E N Parker Astrophys J 128 664 1958 E B Hooper Journal of Propulsion and Power 9 757 1993 APS DPP 2007 3 MAGNETIC NOZZLE LAYOUT Plasma vacuum interface Transition to super Alfv nic flow Sub Alfv nic flow Nozzle wall Super Alfv nic flow Nozzle end Key requirements to magnetic



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