Skip to Main Content
Since 1961, the United States has flown 41 radioisotope thermoelectric generators (RTGs) and one reactor to provide power for 25 space power systems. Thirty-eight of these nuclear power sources on 22 space systems are still in space or on other planetary bodies. This paper summarizes the design and power performance of each of the basic RTG types that have been flown which have been based on telluride and silicon-germanium thermoelectric elements. To date, US radioisotope thermoelectric generators have successfully operated for over 24 years in space. These RTGs have met or exceeded their prelaunch requirements and in so doing they have greatly expanded humanity's knowledge of the universe.