Cathode Current Sharing in Parallel Discharges (Past)

Lauren Chu Steve Synder (JPL) Dan Goebel Richard Wirz

High power solar electric propulsion capabilities have the potential for significantly decreasing the mass and cost of many future NASA exploration missions. Reducing the spacecraft’s mass and complexity of power processing by utilizing Direct Drive power technology will save mission cost, as suggested by studies of high power systems.

Multiple-thruster Direct Drive systems place the thrusters and cathodes parallel in the circuit. The plasma physics of parallel cathode operation is crucial for enabling Direct Drive system technology development, but is presently not well understood. This effort isolates the cathode physics with a thruster-less experiment and aims to investigate basic plasma physics phenomena causing and affecting current-sharing between parallel cathodes.

A small vacuum facility has been set up at the Jet Propulsion Laboratory with two nearly-identical BaO laboratory cathodes in parallel. Preliminary dual cathode tests have demonstrated various degrees of cathode-sharing behavior by changing the cathodes' mass flow rates. In progress are efforts to use electrostatic probes to obtain 2D maps of plasma properties downstream of the cathodes, such as electron temperature, plasma potential, and plasma density.