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Integrity of the Plasma Magnetic NozzleThis report examines the physics governing certain aspects of plasma propellant flow through a magnetic nozzle, specifically the integrity of the interface between the plasma and the nozzle s magnetic field. The injection of 100s of eV plasma into a magnetic flux nozzle that converts thermal energy into directed thrust is fundamental to enabling 10 000s of seconds specific impulse and 10s of kW/kg specific power piloted interplanetary propulsion. An expression for the initial thickness of the interface is derived and found to be approx.10(exp -2) m. An algorithm is reviewed and applied to compare classical resistivity to gradient-driven microturbulent (anomalous) resistivity, in terms of the spatial rate and time integral of resistive interface broadening, which can then be related to the geometry of the nozzle. An algorithm characterizing plasma temperature, density, and velocity dependencies is derived and found to be comparable to classical resistivity at local plasma temperatures of approx. 200 eV. Macroscopic flute-mode instabilities in regions of "adverse magnetic curvature" are discussed; a growth rate formula is derived and found to be one to two e-foldings of the most unstable Rayleigh-Taylor (RT) mode. After establishing the necessity of incorporating the Hall effect into Ohm s law (allowing full Hall current to flow and concomitant plasma rotation), a critical nozzle length expression is derived in which the interface thickness is limited to about 1 ion gyroradius.
Document ID
20100000017
Document Type
Technical Publication (TP)
Authors
Gerwin, Richard A. (Los Alamos National Lab. NM, United States)
Date Acquired
August 25, 2013
Publication Date
December 1, 2009
Subject Category
Spacecraft Propulsion and Power
Report/Patent Number
NASA/TP-2009-213439
E-14974
Funding Number(s)
CONTRACT_GRANT: NASA Order C-32057-G
WBS: WBS 22-973-90-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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