Development of a static vapor feed electrolyzer utilizing an advanced bipolar plate that produces sub-saturated H2 and O2 is proposed. This novel bipolar design can greatly simplify electrolyzer systems, as it eliminates the need for water/gas phase separation, which is particularly challenging in a zero gravity environment. Maintaining water in the vapor phase greatly reduces membrane swelling which should increase durability. Finally, by keeping water in the vapor phase the MEA is not exposed to ion and other contaminants that are carried by a liquid water stream, further increasing durability and simplifying the system by reducing the need for ultra-pure water. The primary goal of this Phase I program is to demonstrate a high-pressure (1000 psi) static vapor feed electrolyzer and demonstrate that the system can operate without purge of the water feed stream for up to 100 hours.