Anode sheath contributions in plasma thrusters
By: John F. Riggs
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1994
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 97
Description: Contributions of the anode to Magnetoplasmadynamic (MPD) thruster performance are considered. High energy losses at this electrode, surface erosion, and sheath/ionization effects must be controlled in designs of practical interest. Current constriction or spotting at the anode, evolving into localized surface damage and considerable throat erosion, is shown to be related to the electron temperature's (T sub e) rise above the gas temperature (T sub o) . An elementary one-dimensional description of a collisional sheath which highlights the role of T sub e is presented. Computations to model the one- dimensional sheath are attempted using a set of five coupled first-order, nonlinear differential equations describing the electric field, as well as the species current and number densities. For a large temperature nonequilibrium (i. e., T sub e > > T sub o), the one-dimensional approach fails to give reasonable answers and a multidimensional description is deemed necessary. Thus, anode spotting may be precipitated by the elevation of T sub e among other factors. A review of transpiration cooling as a means of recouping some anode power is included. Active anode cooling via transpiration cooling would result in (1) quenching T sub e, (2) adding 'hot' propellant to exhaust. and (3) reducing the local electron Hall parameter. However significant technical problems remain. Distribution Limitation(s):
Notes: Thesis advisor(s): Oscar Biblarz.

"March 1994."

Thesis (Degrees of Aeronautical & Astronautical Engineer and M.S. in Astronautical Engineering) Naval Postgraduate School, March 1994.

Includes bibliographical references.

Approved for public release; distribution unlimited.

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US Navy )USN) author.