LAUSR

Thrust and current-voltage characteristics of pulsed cathodic arcs operating in vacuum and ambient air are presented and analyzed. In near vacuum conditions the thrust is proportional to the pulse duration, whereas in atmospheric pressure air the thrust reaches a maximum at a pulse duration of ~5 s and then decreases for longer durations. A thrust model is developed based on contributions from two sources: fast ions and local pressure gradient. According to the model, for a sufficiently short pulse, the arc generates a positive local overpressure that produces additional thrust. Good agreement is obtained between the model and measurements. These results suggest that an optimal arc pulse duration exists for effective momentum transfer to the background gas.