Giner Electrochemical Systems (GES) proposes to develop a cathode liquid feed, proton-exchange membrane electrolyzer stack and system capable of producing 3,600 psi oxygen. We propose to subcontract Hamilton-Sundstrand Human Space Systems (H-S) to share unique state-of-the-art technologies that provide the best path to meeting program objectives. GES will share their data and expertise with high balanced pressure electrolyzers and H-S will contribute their data and expertise in high differential pressure electrolyzer systems. Based on the high pressure anode design concept developed in Phase I, GES will further develop the electrolyzer cell and stack design. In parallel, H-S will develop the key subsystem and control components for a brassboard balance of plant. The program will culminate in the fabrication, assembly, and demonstration of a brassboard high oxygen pressure generation system.