It’s often an afterthought, but the energy source needed to keep a spacecraft running years after we launch it into space is arguably one of the most important pieces of the equation. So, with supplies almost tapped, the U.S. government is producing Plutonium-238 for the first time in decades.
The problem is an interesting one, and had NASA and the DOE not started work now, it could’ve potentially stalled space exploration across the next decade and beyond. Plutonium-238 is typically produced as a byproduct of making nuclear bombs, so when the world governments agreed to stop making the bombs, NASA’s stockpile of battery material started drying up. Currently, there are only 35 pounds of usable material available, which isn’t all that much looking long-term.
Batteries crafted from the hazardous material are currently running the New Horizons probe the just passed Pluto, as well as the Curiosity rover currency ripping around on the Red Planet. It was also used during the Apollo missions. But, there’s only enough left to launch approximately three more spacecrafts. That’s why NASA and the U.S. Department of Energy are working to make some more, though the process is decidedly slow-going. They’ve managed to make 50 grams in two years, but the typical space probe can require as much as 8-9 pounds of the stuff. So, the team will keep churning along.
“This significant achievement by our teammates at DOE signals a new renaissance in the exploration of our solar system,” John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington, said in a statement. “Radioisotope power systems are a key tool to power the next generation of planetary orbiters, landers and rovers in our quest to unravel the mysteries of the universe.”
Though the process can be similar, Popular Science notes Plutonium-238 is different from plutonium used in nuclear weapons and power stations. It’s so useful as a power source because, as plutonium-238 decays into Uranium-234, it gives off massive amounts of heat, which can be harnessed as electric energy in NASA's radioisotope thermoelectric generators (RTGs). Along with producing energy, the heat is also to keep all those fragile electronics from freezing to death in the deeper recesses of space.
As debates rage on over exactly what NASA might do next on its quest to get humans to Mars (and beyond), there’s no denying we’ll need a stockpile of Plutonium-238 to pull it off. It’s encouraging to think we’ll (hopefully) have enough set aside once we finally figure it all out.