By Matt Dozier
â€‹NASAâ€™sÂ New Horizons spacecraftÂ just accomplished one of the most exciting feats in the history of space exploration. After a 9.5-year, 3-billion-mile journey, the missionâ€™s historic flyby of Pluto has provided us with our first-ever closeup views of the frozen world at the edge of the solar system. Itâ€™s a remarkable achievement, one that wouldnâ€™t have been possible without careful planning, ingenuityâ€”and a little help from the U.S. Department of Energy.
In 2006, when NASA engineers were designing New Horizons, they knew that it would need aÂ long-lasting, compact and incredibly reliable power sourceÂ to survive the cold, dark reaches of outer space.
Solar power was out of the question. The spacecraftâ€™s itinerary would take it billions of miles from the center of the solar system into the realm of Pluto and the Kuiper Belt. That far out, the Sun shines with just a tiny fraction of the intensity we see here on Earthâ€”scarcely brighter than the stars in the night sky. Other options like batteries or fuel cells wouldnâ€™t last long enough.
For New Horizons, the answer lay in the power of plutonium.Â Specifically, in aÂ radioisotope thermoelectric generator, or RTG. This simple form of nuclear power, developed by the Energy Department, takes heat from the radioactive decay of plutonium-238 and converts it into electricity using devices called â€œthermocouples.â€ The RTG provides about 200 watts of electricity to the spacecraft.
Used by the United States in space exploration since the 1960s, RTGs are rugged and reliable, with no moving parts to wear out or break. That durability made an RTG the perfect candidate to power a deep-space mission like New Horizons. To build it, NASA turned to DOE’s national labs.
The heat-producing ceramic â€œfuel pelletsâ€ of plutonium dioxide for the RTGâ€”designed and safety-tested by Energy Department scientistsâ€”were manufactured atÂ Los Alamos National LaboratoryÂ in New Mexico, with special iridium and graphite shielding provided byÂ Oak Ridge National LaboratoryÂ in Tennessee. The plutonium-238 itself came from theÂ Savannah River SiteÂ in South Carolina, which produced nuclear fuel for NASA’s spaceÂ missions forÂ nearly three decades.
The final product was assembled atÂ Idaho National LaboratoryÂ in September 2005, just three years after the Energy Department decided to relocate its RTG program there in 2002. Thatâ€™s especially impressive when you consider that an entirely new facility needed to be constructed before the team could even begin to build and test the RTG for New Horizons.
New Horizons has now captivated the world with its breathtakingly detailed images of Plutoâ€™s surface, but it isnâ€™t done exploring. Through the Kuiper Belt and beyond, its RTG will keep it warm and watchful as it ventures into the outer reaches of our solar system.
The Energy Department is thrilled to be part of this momentous journey and to witness these groundbreaking discoveries. Weâ€™re ready to support NASAâ€™s exploration of our universeÂ wherever it takes us.
To learn more about the Energy Departmentâ€™s role in the U.S. space program, check out our interactiveÂ timeline of nuclear-powered NASA missionsÂ through history.
- New Horizons traveled more than 3 billion miles over 9.5 years to reach Pluto.
- At that distance, power sources like solar energy, batteries, and fuel cells fall short.
- Nuclear technology from the Energy Department gave New Horizons the heat and power it needs to explore Pluto and beyond.
See story on DOE website here.
Matt DozierÂ is a digital content specialist in the U.S. Department of Energy’s Office of Public Affairs.
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