The Oxygen Generation Subsystem (OGS), using the Hamilton Standard SPE®, has been successfully tested as a part of the Life Support System Integration Facility (LSSIF) phase II of the Early Human Testing (EHT) Initiative at NASA's Johnson Space Center (JSC).Analysis of the OGS test was conducted. Correlations for oxygen and hydrogen current efficiencies and cell stack voltage with respect to various operating parameters were developed using the LSSIF test data. Analyses of the performance of the two-phase flow air-cooled heat exchanger and the heat loss of the components of the subsystem have also been conducted.A stand-alone OGS model and a simulation model using the CASE/A (Computer Aided System Engineering and Analysis) computer simulation tool have been developed and verified successfully. Both models complement each other to reach the objectives of supporting the analysis of the Life Support System Integration Facilities (LSSIF) performance and as general tools for future system performance analyses.Development of both models, including the transient thermal behavior and electrolysis mechanism of the cell stack, is presented in this paper. Comparison of the simulation results against the LSSIF test data shows that both models can predict the OGS performance reasonably well.An optimization analysis of the OGS operating parameters to maximizes the O2 and H2 production yields and to minimize the power consumption has been conducted. The optimum cell stack operating temperatures for various OGS input currents are included in this paper.