NASA needs advanced power-conversion technologies to improve the efficiency and reliability of power conversion for space exploration missions. We propose to develop a Stirling generator to meet NASA needs. Our Stirling generator adapts technology we have developed for high-reliability long-life (> 10 years) space-based Stirling-cycle cryocoolers and proprietary compressor and expander technology. Our compressor and expander technology enables near-isothermal compressions and expansions, which allow our Stirling generator to achieve a high percentage of the Carnot thermal efficiency. In Phase I, we will generate a preliminary design of our Stirling generator and project its efficiency. In Phase II, we will build and demonstrate a prototype Stirling generator and deliver the prototype to NASA for functional and environmental testing. In Phase III, we will build and sell Stirling generators for many government and private-sector applications.