We propose a reservoir cathode to improve performance in both ion and Hall-effect thrusters. We propose to adapt our existing reservoir cathode technology to this purpose. Reservoir cathodes are the only emission sources that are capable of providing the necessary current density (>5.0 A/cm2) and life (>100,000 hours) for next generation high-power thrusters. More powerful thrusters are needed for interplanetary and lunar missions, including earth escape and near-earth space maneuvers. Reservoir cathodes are able to provide sufficient new barium to the cathode surface to overcome the high barium removal rates in ion engines. We have many years' experience developing reservoir cathodes. The key challenge is the stresses exerted on the cathode tube due to differential expansion and large temperature excursions. These lead to fracturing and weld failure. Our innovation solves this problem. In Phase I, a prototype is built and tested. In Phase II, we optimize for specific ion engines.