NASA is running out of nuclear fuel needed for its deep space exploration.
The end of the Cold War's nuclear weapons buildup means that the U.S. space agency does not have enough plutonium for future faraway space probes — except for a few missions already scheduled — according to a new study released Thursday by the National Academy of Sciences.
Deep space probes beyond Jupiter can't use solar power because they're too far from the sun. So they rely on a certain type of plutonium, plutonium-238. It powers these spacecraft with the heat of its natural decay. But plutonium-238 isn't found in nature; it's a byproduct of nuclear weaponry.
The United States stopped making it about 20 years ago and NASA has been relying on the Russians. But now the Russian supply is running dry because they stopped making it, too.
The Department of Energy announced on Thursday that it will restart its program to make plutonium-238. Spokeswoman Jen Stutsman said the agency has proposed $30 million in next year's budget for preliminary design and engineering. The National Academy's study shows why it is needed, she said.