I. Funaki, H. Kuninaka, K. Toki, Y. Shimizu, K. Nishiyama, Y. Horiuchi
Journal of Propulsion and Power, 18(1) 169-175, Jan, 2002 Peer-reviewed
An ion beam optics for a 10-cm-diam 400-W-class microwave discharge ion thruster was fabricated and its applicability to a long-term space mission was demonstrated. The optics consists of three 1-mm-thick flat carbon-carbon composite panels with approximately 800 holes that were mechanically drilled and positioned with ±0.02-mm accuracy. When mounted on an aluminum ring, spacing for the three grids was kept at 0.5 mm by three sets of spacers. The thruster produced an ion beam current of 140 mA with a microwave power of 32 W for plasma generation and a total acceleration voltage of 1.8 kV. Although the grid is sputtered by the impingement of slow ions produced in charge-exchange collisions between fast beam ions and neutral atoms leaking from the engine, the grid showed only slight damage even after an 18, 000-h endurance test. Also, other qualification tests including a mechanical test under launch conditions as well as a thermal vacuum test simulating the spacecraft thermal environment were successfully completed. Hence, the grid system was qualified for spacecraft propulsion. © 2002 American Institute of Aeronautics and Astronautics, Inc.