.. - A Radioisotope Thermoelectric Generator (RTG) is a type of nuclear battery that uses the heat generated by the natural radioactive decay of plutonium-238 to produce electrical power[2][5]. The heat is converted into electricity by an array of thermocouples, which are devices that convert thermal energy directly into electrical energy[3][5]. The RTGs are lightweight, compact, and extraordinarily reliable, making them ideal for use in spacecraft power systems[1].
The RTGs consist of three critical components: the radioactive isotope, the thermocouples, and the thermal insulation[6]. The radioactive isotope is central to the RTGs design and provides the heat from which the rest of the design produces electricity[6]. Most designs use Plutonium-238, Strontium-90, or Americium-241 for their power density, half-life, and radioactive shielding requirements[6]. The thermocouples are connected to each other in a closed loop and generate an electric current when the two metals are at different temperatures[3][5]. The thermal insulation is used to minimize heat loss and maximize the temperature difference between the hot fuel and the cold environment of space[6].
RTGs have been used to power more than two dozen U.S. space missions, including the Cassini probe, Voyager probes, New Horizons, and Curiosity rover[5][6]. They are capable of producing heat and electricity under the harsh conditions in deep space for decades without any maintenance[5].
Citations:
[1] Radioisotope Thermoelectric Generators (RTGs) | Cassini - NASA Solar System Exploration https://solarsystem.nasa.gov/missions/cassini/radioisotope-thermoelectric-generator/
[2] Radioisotope thermoelectric generator - Wikipedia https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator
[3] What are radioisotope thermoelectric generators? https://www.qrg.northwestern.edu/projects/vss/docs/power/1-what-are-rtgs.html
[4] An Overview of Radioisotope Thermoelectric Generators - Stanford University http://large.stanford.edu/courses/2013/ph241/jiang1/
[5] What is a Radioisotope Power System? - Department of Energy https://www.energy.gov/ne/articles/what-radioisotope-power-system
[6] Radioisotope thermal generator - Energy Education https://energyeducation.ca/encyclopedia/Radioisotope_thermal_generator