This proposal is responsive to NASA SBIR Topic X10.01, specifically, the need for efficient small- to medium-scale hydrogen liquefaction technologies, including domestically produced wet cryogenic turboexpanders. Future NASA missions will require hydrogen liquefaction systems for spaceport, planetary, and lunar surface operations. A critical part of these systems is the cryogenic expansion turbines, which must be designed for high-speed operation and long life, and must be robust against the pressure and momentum excursions and the surface tension effects associated with two-phase flow. On the Phase I project, we identified and optimized a liquefaction system for spaceport operations. We demonstrated by analysis the benefits of using expansion turbines in the product stream instead of the customary Joule-Thomson throttle. We designed a set of high-performance turbines for use in these systems. On this Phase II project, we will demonstrate cryogenic expansion turbines for use in hydrogen liquefiers. The expansion turbines will be reliable, compact, lightweight, and efficient and will be able to operate in a two-phase system. They will have the innovative feature of recovering the expansion work through use of an alternator instead of dissipating work through a brake wheel. This approach greatly simplifies controls, improves reliability, and reduces system mass and input power.