What do spacecraft and smoke alarms have in common? A material commonly used to detect smoke on Earth could soon power robotic missions to other planets.
Previous spacecraft travelling to the outer solar system have been powered by the decay of plutonium-238. The isotope is running out, though.
The US stopped producing plutonium-238 in the 1980s and NASA has nearly used up the leftovers from that period. The US Congress has so far baulked at paying the many millions of dollars it would take to restart production.
Russia has some leftover material of its own that it could sell, but it is not yet clear if negotiations with the US will result in a deal.
This could mean that there will not be enough plutonium-238 for a joint NASA and European Space Agency mission to Jupiter and its icy moon, Europa, which is planned for launch around 2020.
ESA now plans to build up an alternative supply of americium-241. In smoke detectors, the material's decay helps to make ions that trigger an alarm when smoke particles attach to them.
"We really don't know of any other way to have an electric power supply going into the deep solar system," says David Southwood, ESA's director of science and robotic exploration.
Americium-241 decays more slowly than plutonium-238, potentially allowing for longer missions, says Ralph McNutt of Johns Hopkins University in Baltimore, Maryland, who co-authored a report on the plutonium-238 shortage in the US.
On the downside, it takes more of the stuff to supply one unit of power, which could be a drawback for space missions, in which weight must be kept at a minimum, he says. "When you're trying to do interplanetary missions, really every kilogram counts," he says.
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