A 15,000-hour cyclic endurance test of an 8-centimeter-diameter electron bombardment mercury ion thruster

A laboratory model 8-cm thruster with improvements to minimize ion chamber erosion and peeling of sputtered metal was subjected to a cyclic endurance test for 15,040 hours and 460 restarts. A charted history of several thruster operating variables and off-normal events are shown in 600-hour segments at three points in the test. The transient behavior of these variables during a typical start-stop cycle is presented. Performance and operating characteristics were nearly constant throughout the test except for a change in the accelerator back-streaming limit. Findings of the post-test inspection confirmed most of the expected results. Charge-exchange ions caused normal accelerator grid erosion. The workability of the various design features have been substantiated, and attainable improvements in propellant utilization efficiency should significantly reduce accelerator erosion.