The design of a space power system yielding maximum performance is a laborious task requiring implicit knowledge of many criteria. The labor involved with previous techniques is not conducive to the analysis of systems employing novel fluids. To circumvent these problems, a new method of analysis of saturated and superheated Rankine cycles is presented. The approach employed equates maximum performance with the minimum radiating area which can then be linked to a particular cycle through thermodynamic relationships. The analysis is concluded by utilizing a semiempirical technique to determine turbine efficiencies. The new approach which is applicable to all fluids is then used to evaluate three typical cycles.