Erosion Processes of the Discharge Cathode Assembly of Ring-Cusp Fridded 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.
A. D. Gallimore et al., "Erosion Processes of the Discharge Cathode Assembly of Ring-Cusp Fridded Ion Thrusters," Journal of Propulsion and Power, American Institute of Aeronautics and Astronautics (AIAA), Jan 2007.
The definitive version is available at http://dx.doi.org/10.2514/1.27897
Mechanical and Aerospace Engineering
Keywords and Phrases
Electrostatic Probe Diagnostic Technique; Ion Thruster; Probe Positioning System
Article - Journal
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