Electropositive surface layer MPD thruster cathodes

Conference · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5523448

Chamberlain, F R; Kelly, A J; Jahn, R G

Lithium and barium oxide have been used to generate electropositive surface layers on tungsten cathodes in low power steady state MPD thruster experiments. The electropositive surface layer decreases the cathode work function, resulting in substantial reductions in the steady state cathode operating temperature and erosion rate. Cathode temperature is reduced by 300 degrees with a lithium surface layer and by 800 degrees with a barium oxide surface layer at a 500 ampere thruster current level. These temperature reductions substantially reduce the calculated steady state evaporative erosion rate of the cathode by factors of 20 and 10,000 respectively. Cold cathode startup erosion is also reduced dramatically. The surface melting and arc cratering that is characteristic of pure tungsten cathodes does not occur with an electropositive surface layer cathode. In addition to reducing cathode erosion, the use of these materials increases thruster efficiency. 12 refs.

• OSTI ID: 5523448
• Report Number(s): AIAA-Paper--89-2706; CONF-8907118--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420200* -- Engineering-- Facilities
Equipment
& Techniques
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CATHODES
CHALCOGENIDES
ELECTRODES
ELEMENTS
EROSION
FLUID MECHANICS
HYDRODYNAMICS
LAYERS
LITHIUM COMPOUNDS
LITHIUM OXIDES
MAGNETOHYDRODYNAMICS
MECHANICS
METALS
OXIDES
OXYGEN COMPOUNDS
PLASMA
PROPULSION
SURFACES
THRUSTERS
TRANSITION ELEMENTS
TUNGSTEN