ABSTRACT
This chapter provides in-depth coverage of the radioisotope thermoelectric generator (RTG) as a spacecraft power source in long-duration missions far away from the sun. The fundamentals of thermoelectric (TE) converters are first discussed, followed by single-stage unicouple and multistage multicouple TEs and their construction and assembly details. The RTG’s electrical models and the current-voltage-power and efficiency characteristics are illustrated. The optimum operating voltage to extract the maximum possible output power from an RTG is established to be one-half of the open-circuit voltage. The effects of temperature and radioactive decay (aging) on the maximum power output and the TE conversion efficiency are reviewed. Various types of RTGs—established and advanced—are evaluated for their applicability. A special application of TE for cooling inside a very small and delicate part is briefly presented.
