NASA

The Voyager 1 spacecraft is among NASA's fleet powered by Plutonium-236.

By Mike Wall Space.com

NASA will now foot the entire bill for the United States' production of plutonium-238 spacecraft fuel, which recently started up again for the first time in a quarter-century.

The space agency had been splitting costs for the reboot with the U.S. Department of Energy, which actually produces plutonium-238. But NASA is the only projected user of the stuff, so the arrangement changed in the White House's federal budget request for 2014, which was unveiled earlier this month.

"Since the (Obama) administration has a 'user pays' philosophy, we are now in a position to pay for basically the entire enterprise, including the base infrastructure at DOE," NASA Chief Financial Officer Beth Robinson said in an April 10 press conference. "We'll be partnering with DOE in the next couple of months to figure out how to best do this, and how to streamline the program to produce plutonium-238."[Nuclear Generators Power NASA Probes (Infographic)]

Plutonium-238 is not a bomb-making material, but it is radioactive, emitting heat that can be converted to electricity using a device called a radioisotope thermoelectric generator. For decades, RTGs have powered NASA probes to destinations in deep space, where sunlight is too weak and dispersed to be of much use to a robot.

For example, the agency's twin Voyager spacecraft, which are knocking on the door of interstellar space, are both RTG-powered. So is the Mars rover Curiosity, whose observations recently helped scientists determine that the Red Planet could once have supported microbial life.

The DOE stopped producing Pu-238 in 1988, after which NASA began sourcing the fuel from Russia. But the agency received its last Russian shipment in 2010, and supplies have been dwindling ever since, worrying many scientists and space-exploration advocates.

So NASA and the DOE have been working together on a Pu-238 restart, which officials from both agencies have estimated will cost between $75 million and $90 million over five years.

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NASA now footing entire bill for plutonium production