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The manifestation of Alfven's hypothesis of critical ionization velocity in the performance of MPD thrustersThe role of Alfven's critical ionization velocity in the performance of the self-field MPD thruster has been investigated. The existence of a well defined characteristic velocity can be attributed to an ionization process involving the production of a population of suprathermal electrons by an electrostatic instability. It is shown that for the MPD thruster plasma, suprathermalization of electrons via this electrostatic instability can only happen if ions are initially accelerated to velocities larger than the Alfven critical ionization velocity. When this occurs the mechanism will be initiated and the ions decelerated to velocities near the critical velocity. This mechanism ceases to be limiting when all neutrals are ionized. A model of MPD thruster terminal behavior, incorporating Alfven's hypothesis, is presented. Experiments with three different propellants reveal that operation at values of the current squared to total mass flow ratio corresponding to the Alfven critical velocity is marked by a transition wherein low frequency voltage oscillations and a notable change in the voltage-current dependence occurs. One major result of this study is the demonstration that the Alfven critical velocity is not a fundamental limitation on MPD exhaust velocity.
Document ID
19860026254
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Choueiri, E. Y.
(Princeton Univ. NJ, United States)
Kelly, A. J.
(Princeton Univ. NJ, United States)
Jahn, R. G.
(Princeton University NJ, United States)
Date Acquired
August 12, 2013
Publication Date
September 1, 1985
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
AIAA PAPER 85-2037
Accession Number
86A10992
Funding Number(s)
CONTRACT_GRANT: JPL-954997
Distribution Limits
Public
Copyright
Other

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