ABSTRACT
Typically, long-duration space missions to the outer planets require the use of nuclear-powered electrical and heat sources for the spacecraft. The Cassini spacecraft (launched on the Titan IV/Centaur launch vehicle) carries three radioisotope thermal-electric generators (RTGs), as illustrated in Figure 8-1. An RTG, pictured in cutaway in Figure 8-2, converts the energy from nuclear decay (predominately alpha decay) into heat and then electricity. As shown in Figure 8-2, an RTG has an aluminum housing that contains (1) heat-source modules of radioactive plutonium dioxide (PuO2) surrounded by graphite and (2) components needed for thermoelectric conversion of energy generated by decay of the radioactive PuO2. An RTG is generally cylindrical, with a diameter of about 0.43 m and a length of about 1.17 m.
