A significant proportion of the total weight in a large spaceborne electrical power plant is associated with the radiator. The belt space radiator offers a concept in the rcjcctdon of heat in a space environment that may theoretically reduce the radiator weight by more than 60% if thermal contact resistance between the revolving belt and heat source drum is sufficiently small. A theoretical analysis of thc effects of contact resistance on optimum weight applicable to a revolving belt radiator with a stationary condenser drum, as well as to a system with revolving condenser drum and geometrically stationary belt configuration for,a 1-megawatt power output system, is given. It is found that the effective contact heat transfer film coefficient must be approximately 400 Btu/hr-ft/sup 2/- deg F to realize significant weight savings. If this value of film coefficient can be obtained, the belt radiator must be considered as a replacement for conventional header and tube radiators for spaceborne power plants. (auth)