What is isotope? They have extra neutrons and they become radioactive, releasing protons, neutrons, and energy in a process called decay. This is a much different technique than that used by nuclear power stations on Earth. Nuclear reactors generate heat by fission, a process in which atoms are split by a bombardment of neutrons. In an RTG, heat is generated only by the natural radioactive emissions of the isotope contained in it.

After the heat is obtained by radioactive decay of isotope, how does the heat convert into electricity? This can be done by thermocouple. Thermocouple is made of two kinds of metal that can both conduct electricity. They are connected to each other in a closed loop. If the two metals are at different temperatures, an electric potential will exist between them. When an electric potential occurs, electrons will start to flow, making electric current. This is called the Seebeck effect.

Radioisotope thermoelectric generators employ radioactive materials to produce heat and make use of a principle of electrics known as Seebeck effect.

 

This generator has no moving parts. RTGs have been used as power sources in satellites, space probes, and unmanned remote facilities such as a series of lighthouses built by the former Soviet Union inside the Artic circle. 

 

RTGs are usually the most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit.

 

The RTG was invented in 1954 by Mound Laboratories scientists Ken Jordan and John Birden. They were inducted into the National Inventors Hall of Fame in 2013. Jordan & Birden worked on an Army Signal Corps contract (R-65-8- 998 11-SC-03-91) beginning on January 1, 1957, to conduct research on radioactive materials and thermocouples suitable for the direct conversion of heat to electrical energy using Polonium-210 as the heat source. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg Ohio, under contract with the United States Atomic energy Comission. The project was led by Dr. Bertram C. Blanke. 

The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, aboard the Navy Transit 4A spacecraft. One of the first terrestrial uses of RTGs was in 1966 by the US Navy at uninhabited Fairway Rock in Alaska. 

By: Putri Annur Khaleeda

1)    New Horizons

2)    Voyager 1 and Voyager 2

3)    Cassini-Huygens

4)    Galileo