Space Programs

Satellites and Spacecraft

How does an RTG work?

Radioisotope thermoelectric generators (RTGs) are not nuclear power plants in space. They are heavily shielded containers that hold several kilograms of radioactive isotopes such as plutonium-238, and include equipment that converts the heat released by the isotopes’ radiative decay into electrical power. The Cassini spacecraft, for example, carries three RTG units, each of which started off with about seventeen pounds (eight kilograms) of plutonium-238 and generated about 300 watts of electrical power.


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