In the late 1960's, the SPE water electrolyzer project was spun off from the SPE fuel cell project when the first chemically stable, long life, perfluorocarbon ion exchange membranes became available. Since that time a variety of SPE water electrolyzer products have been developed and put into production. One of these products was developed for the production of life support oxygen in nuclear submarines. Over 30 systems containing SPE water electrolyzers have been delivered to the U.K. Royal Navy. Successful U.S. Navy sea trials have recently been completed on the SPE water electrolyzer system and that system is about to go into production for the U.S. Navy nuclear submarine fleet. Overviews of these two programs will be provided.The identical cell structure used in the nuclear submarine SPE water electrolyzer programs has recently been incorporated into a life support water electrolyzer for the Space Station Freedom microgravity application for the Boeing Aerospace and Electronics Company. This system design features microgravity liquid/gas static phase separators and the use of processed hygiene water as the feedstock. A top level system schematic will be provided along with details of the static phase separators and a summary of overall electrolyzer performance.