NASA is investigating advanced turboelectric aircraft propulsion systems that utilize superconducting motors to drive a number of distributed turbofans. In an early-stage concept, two superconducting turbine generators, mounted on each of the wing tips, are used to supply electrical power to 16 superconducting motors. Conventional electric motors are too large and heavy to be practical for this application, and so superconducting motors are required. These would operate at a temperature near that of liquid hydrogen, between 20 and 65 K. In order to improve maneuverability of the aircraft, variable speed power converters would be required to throttle power to the turbofans. The low operating temperature and the need for lightweight components that place a minimum of additional heat load on the refrigeration system opens the possibility of incorporating extremely efficient cryogenic power conversion technology. A complete study of cryogenic power conversion equipment for use in this application is the focus of this proposal. MTECH has designed, built, and tested a number of cryogenic inverters for different applications, and will adapt the cryogenic power technologies it has developed to the NASA application in this program.