Performance of a cesium bombardment ion engine with a self-rectifying discharge and automatic controls.

Abstract

The concept of a self-rectifying engine is based on the fact that a probe immersed in a plasma forms a quasi-rectifying contact with the plasma. A cesium bombardment engine was modified by replacing the cylindrical anode with multiple anode segments. These segments were driven from a center-tapped transformer with the center tap connected to the engine cathode. Alternate segments functioned as the anode when they were positive with respect to the plasma. This maintained the discharge and a continuous ion beam was extracted. The efficiency of this engine was found to be the same as that of the engines previously used on the 3700 and 8200 h life tests. The necessary circuitry for starting and power control was determined, and a method for automatic discharge power control was developed which maintained engine operation at maximum efficiency while correcting for input line voltage variations as well as shifts in engine performance. Excellent stability was achieved by using an error-integrating feedrate control loop. Turn-on time from standby to full thrust was less than 60 sec.