The proposed innovation is a very lightweight fuel cell that uses passive techniques to move reactants into the fuel cell and remove the byproduct water and heat from the fuel cell. When coupled with a state-of-the-art composite cryogenic reactant tanks, the overall energy density of the fuel cell power system is projected to be approximately 1,000 watt-hr/kg which is 10X the current state-of-the-art lithium batteries. Such a dramatic increase in energy density is a disruptive and much needed breakthrough in energy storage for NASA's portable power needs. The cross section of the UED fuel cell shows the fuel cell bipolar assembly and the membrane electrode assembly. The stack of cells are provided H2 and O2 on perpendicular faces of the stack. The water is separated from the incoming oxygen by micro-grooved plates that wick the water to the oxygen manifold and ultimately to the water exit of the stack where a high bubble-point gas/liquid membrane separator allows the water to leave the stack, but prevents incoming oxygen from escaping with the water. To minimize mass, the bipolar plates are expected to be made of plastic doped with an electrically conductive filler laminated with pyrolytic graphite for heat conduction, and the endplates structures are expected to be stiff corrugated plastic.