Title: Nuclear Reactors for Space - World Nuclear Association
Headings: Nuclear Reactors and Radioisotopes for Space
Nuclear Reactors and Radioisotopes for Space
Radioisotope systems – RTGs
Fission systems – heat and propulsion
Early US programme: 1960s to 1980s
Later US programmes: 1990s on
US Project Prometheus: 2003-2007
Current US programme
Russian fission systems
Space Reactor Power Systems
Radiation in space
Notes & references
General sources
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Nuclear Reactors and Radioisotopes for Space
(Updated May 2021)
Radioisotope power sources have been an important source of energy in space since 1961. Nuclear fission reactors for space have been used mainly by Russia, but new and more powerful designs are under development in both the USA and Russia. Plutonium-238 is a vital power source for deep space missions. Nuclear power reactors use controlled nuclear fission in a chain reaction. With the use of neutron absorbers, the rate of reaction is controlled, so the power depending on the demand. Radioisotope Thermoelectric Generators (RTGs) are an alternative source of power where a chain reaction does not take place. The power depends on the initial amount of the radioisotope used as fuel and the power is provided by converting the heat generated by radioactive decay of the radioisotope into electricity using thermocouples. Most RTGs use plutonium-238. With the use of RTGs, the power generated cannot be varied or shut down so supplementary batteries need to be taken into account for the peak times. RTGs are used when spacecraft require less than 100 kW. Above that, fission systems are much more cost effective than RTGs.