Radioisotope thermoelectric generator

A power source that converts heat released by radioactive decay into electricity through the Seebeck effect. It has no moving parts and can supply power for decades.

Seebeck effect: The production of voltage across a material when its ends are held at different temperatures. A temperature difference across thermoelectric materials produces the generator’s electrical output.
Voyager program: NASA’s pair of robotic probes launched in 1977 to explore the outer planets and interstellar space. Voyager’s generators have powered instruments and communications far beyond the reach of useful solar power.
Radioisotope heater unit: A compact device that uses radioactive decay heat to warm spacecraft components without generating electricity. It uses the same heat source but provides warmth rather than electrical power.
Nuclear safety: The practices and systems used to prevent nuclear accidents and limit harm from radioactive materials. Generator fuel must remain contained during handling, launch accidents, and mission operations.
Thomas Johann Seebeck: A German physicist who discovered in 1821 that a temperature difference between conductors can produce an electrical current. His discovery underlies the thermoelectric conversion used in these generators.
Thermoelectric material: A material that converts temperature differences into electrical voltage or electrical current into heating or cooling. Its thermoelectric properties determine how efficiently decay heat becomes electricity.
Cassini–Huygens: A NASA–European Space Agency mission that studied Saturn, its rings, and its moons from 2004 to 2017. Cassini used radioisotope generators to operate far from the Sun.
Dynamic radioisotope power system: A radioisotope power system that converts decay heat to electricity using moving machinery, such as a Stirling engine. Dynamic systems can be more efficient but add moving components absent from thermoelectric generators.
Radiation shielding: Materials and structures used to reduce exposure to ionizing radiation. Shielding limits radiation reaching spacecraft instruments and, during preparation, personnel.
Radioisotope power system: A device or system that uses radioactive decay to provide electrical or thermal power. The thermoelectric generator is a prominent electrical design within this broader family.

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