Erosion processes of the discharge cathode assembly of ring-cusp gridded ion thrusters

An ion-thruster discharge-cathode-assembly erosion theory is presented based on near-discharge-cathodeassembly NSTAR plasma measurements and experimental results for propellant flow rate effects on ion number density. The plasma-potential structures are used in an ion-trajectory algorithm to determine the location and angle of bombarding ions at the discharge-cathode- assembly keeper. These results suggest that the plasma-potential structure causes a chamfering of the discharge-cathode-assembly keeper orifice. Results from tests with an instrumented discharge-cathode assembly show that increasing propellant flow rate causes a decrease in keeperorifice ion number density, most likely due to charge-exchange and elastic collisions. Combining these two results, the known wear-test and extended-life-test discharge-cathode-assembly erosion profiles can be qualitatively explained. Specifically, the change in the wear profile from the discharge-cathode-assembly keeper downstream face to the keeper orifice for the extended-life test may be a result of the reduction in discharge-cathode-assembly propellant flow rate when the thruster operating point is changed from TH 15 to TH 8. Copyright © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Duke Scholars

Author Alec Gallimore Thomas Lord Department of Mechanical Engineering and Materia ...