In order to address the NASA lunar mission, DESC proposes to develop a proton exchange membrane (PEM) closed-loop pure oxygen fuel cell for application to lunar surface exploration, building upon DESC's expertise and fundamental demonstrations in closely related technology. Building upon the Phase I project, the static feed fuel cell hardware will be scaled up approximately three times in active area. The single-cell performance of the larger cell will be compared against the smaller cell. Sub-scale stacks will be tested for durability. The number of cells per stack will be increased as the thermal management and mass transport phenomena permit. Thermal modeling will be conducted to predict the level of heat removal required by scaled-up stacks. Thermal management techniques will be investigated to permit effective scale-up. Flight cell stack and system design will be undertaken at the concept level.