NASA plans to produce cryogenic oxygen and hydrogen to power regenerative fuel cells for lunar surface exploration. The oxygen and hydrogen will be produced by electrolysis of water from In Situ Resource Utilization reactors. The electrolysis products will be warm high-pressure gases, requiring significant cryocooler power to achieve the desired storage conditions. This power can be reduced by expanding the gases adiabatically from the electrolysis pressure to storage pressure. We propose to develop innovative turboalternators to maximize this effect and convert the extracted fluid power into useful electric power. Small flow rates and high fluid densities require turbine rotors that are extremely small and operate at high speeds. Cryogenic gas bearings and miniature rotor fabrication techniques are key features that create high efficiency in our approach. The gas bearings also enable reliable, long-life, maintenance-free operation. The proposed development will leverage decades of Creare experience with cryogenic gas-bearing turbomachines. In Phase I, we will develop optimized turboalternator designs by conducting trade studies, specifying design details, analyzing performance, and demonstrating bearing operation with two-phase rotor flow. During Phase II, we will fabricate a prototype turboalternator and measure its performance at representative operating conditions.