Radioactive substances such as plutonium-238 oxide naturally generate heat as they spontaneously transform into other elements.
NASA engineers are harnessing this heat to develop the next generation of spacecraft batteries called radioisotope thermoelectric generators, or RTGs.
RTGs have powered NASA’s twin Voyager probes since their launch in 1977; more than 16 billion kilometres away, the Voyagers are the most distant spacecraft from Earth and are still going.
RTGs have also enabled many other missions that have sent back a wealth of science results, including NASA’s Mars Curiosity rover and the New Horizons mission, which flew by Pluto in 2015.
NASA scientists have proposed a next-generation power system called an eMMRTG, which stands for Enhanced Multi-Mission Radioisotope Thermoelectric Generator.
The system relies on materials called skutterudites, which have unique properties that make them especially useful for power systems. They conduct electricity like metal, but heat like glass.
An eMMRTG would provide 25% more power than Curiosity’s generator at the start of a mission, according to current analyses.
And since skutterudites naturally degrade more slowly that the current materials in the MMRTG, a spacecraft outfitted with an eMMRTG would have at least 50% more power at the end of a 17-year design life than it does today.
“Having a more efficient thermoelectric system means we’d need to use less plutonium,” said Sabah Bux, a technologist at NASA’s Jet Propulsion Laboratory who works on thermoelectric materials.
“We could go farther for longer and do more.”
Hear more from Bux in the video above.