THE LAST OF NASA’S FUEL

Abstract

STORMS ON JUPITER, Saturn’s spectacular rings, and even the outer reaches of the solar system have all been glimpsed thanks to the radioactive warmth of plutonium-238. That’s because the substance is at the heart of radioisotope power supplies that generate electricity for the spacecraft that journey to places where sunlight is faint—essentially anything past Mars. But a shortage of 238 Pu threatens to make historic missions such as Voyager, Cassini, and New Horizons the last of their kind. The U.S. hasn’t produced 238 Pu since the late 1980s, and the remaining stockpile—both from U.S. production and from purchases from Russia—has already been allotted to a handful of missions. Since 1994, scientists at NASA and the Department of Energy have tried to restart 238 Pu production, says Stephen G. Johnson, director of Space Nuclear Systems & Technologies at Idaho National Laboratory (INL), in Idaho Falls. None of these efforts, however, has managed to get ...