The thermal analysis of component elements of space radiators is described. Elements include rectangular and circular plates of uniform thickness, triangular and trapezoidal fins, and constant temperature-gradient fins. A complete condenser and a radiator are analyzed and illustrative examples given. The thermal analyses produced relationships between the physical properties and dimensions, element and environmental temperatures, and rates of heat transfer. These are shown graphically for all types of elements. The optimum proportions of space radiator elements having the greatest ratio of heat radiation rate per pound of weight are also indicated graphically, and procedures for their calculation are shown. The discussions on condensers and radiators include dimensional-thermal relationships and weight-optimizing procedures for complete units.