A preliminary design of a Life Support System (LSS) has been developed as part of an ongoing comprehensive trade study of advanced processor technologies and system architectures for an Initial Lunar Outpost. The design is based on a mission scenario requiring intermittent occupation of a lunar surface habitat by a crew of four. It incorporates physiochemical process technologies that were considered for Space Station Freedom. A system-level simulation model of the design was developed to obtain steady-state material balances for each LSS processor. The mass flow rate predictions were used to obtain estimates of the LSS mass, volume, and power consumption by means of processor sizing correlations that were extrapolated from Space Station Freedom processor designs. The results were used to analyze the impacts of varying crew size, mission duration, processor operation strategy, and crew cabin loads on the LSS mass, average power consumption, volume, periodic resupply mass, and waste accumulation rates. The merits of the design were quantified relative to an open-loop LSS, and the implications of this assessment for future LSS research and technology development were identified. Finally, enhancements to the current analysis and questions to investigate during the next phase of the study were identified.