Sub-Millimeter C(f)/C Grids For High Power Ion Propulsion Engines

The high specific impulse and efficiency of ion propulsion thrusters has increased the popularity of these devices for a growing number of proposed missions, such as planetary and deep space, longer station keeping mission lifetimes, and tighter geosynchronous orbit tolerances. Grid erosion is one of the major life limiting phenomena for operating ion thrusters and carbon/carbon composite grids have shown to exhibit at least a 5 fold reduction in the erosion rate.Ceramic Composites Incorporated proposes a novel, low-cost fabrication approach for braided carbon/carbon composite grids with sub-millimeter hole sizes and narrower screen spacing. The thrust per unit beam area is directly proportional to the number of holes in the screen and accelerator grids, thus the smallest possible hole sizes and largest hole density potentially correspond to the maximum thrust density. The high thrust densities enable the accomplishment of a prescribed mission using either smaller thrusters or a smaller number of larger thrusters. A unique approach will be developed to fabricate a woven fiber preform containing sub-millimeter holes, which will be rapidly densified with pyrolytic carbon via chemical vapor infiltration. The grids will be evaluated to determine the ion extraction and other key parameters.