How a plutonium shortage may hobble future deep-space missions.
The end of the Cold War is obviously a good thing, but one of its unintended side effects is starting to sting NASA in a big way: They’re running out of nuclear fuel. Sending spacecraft farther than Mars severely limits the practicality of using solar panels, and most of the missions to the outer planets have relied on radioisotope thermoelectric generators (RTGs) for their power. These compact devices generate up to 300 watts of electricity through the decay of plutonium-238 (Pu-238), and a mere 8 pounds of fuel can power a space probe for decades. Voyager 1 and 2, Cassini, Galileo and the Viking landers on Mars all used RTGs. In fact, such a device is being used on the new Mars rover, Curiosity, which will eliminate the issues Spirit and Opportunity had with dusty solar panels, battery degradation and the long, dark Martian winters.
Pu-238 is a non-weapons-grade isotope that generates heat as it decays. It hasn’t been produced in the United States since the late 1980s, and NASA has been purchasing its supply from Russia since 1993. The problem is that Russia is getting stingy with its increasingly pricey plutonium reserves. Efforts have been made to restart domestic plutonium production, but there are obstacles, both political and economic. Plus, for technical reasons, it would take at least seven years from the date of funding before production could begin. NASA currently has enough Pu-238 for perhaps two new missions before it’s all gone.”