A major safety requirement imposed by the AEC on the utilization of radioisotopes as heat sources in direct cycle thrustors is that the fuel temperature will never exceed its melting temperature. This design condition implies low thrustor thermal efficiency. One promising concept for recovering some of this energy loss is a combined thrustor and thermoelectric generator. Analytical investigations indicate that this combined unit powered by four kilowatts of radioisotope heat source can produce typically 0.1 pound thrust at specific impulses greater than 750 seconds and an electrical power output of 50 watts. Under no propellant flow (zero thrust) conditions, the same unit can provide 150 watts of electric power.