Concept, design approaches suited to space nuclear power systems in the range of 20 kWe

Studies of 20 kWe space nuclear power systems are discussed. In addition to the fast-spectrum, liquid-metal-cooled reactor presently considered as a reference, shorter term gas- and Na(K)-cooled thermal spectrum reactors are being investigated. The need for adequate ZrH moderator temperature conditions is satisfied through a Brayton cycle conversion subsystem featuring two separate, high-temperature heat pipes and low-temperature pumped loop radiators. The penalty in efficiency and in radiator area, resulting from the desired lower reactor inlet temperature, can be limited, particularly in the case of the higher temperature, gas-cooled reactor system. A multiple, pivoting-tube, low-temperature radiator concept is proposed; it avoids an extension of the related structural support frame beyond the conversion subsystem region in flight configuration. Arrangements peculiar to small reactors and two-turbogenerator diagrams for reliability purposes are presented. Provisional, not yet optimized, thermal management mass estimates are evaluated