NASA has been testing a fission reactor for powering spacework. They are calling it “KRUSTY” (Kilopower Reactor Using Stirling TechnologY), and it is not clowning around.
*Kilopower is a small, lightweight fission power system capable of providing up to 10 kilowatts of electrical power – enough to run several average households – continuously for at least 10 years. Four Kilopower units would provide enough power to establish an outpost. …
The prototype power system uses a solid, cast uranium-235 reactor core, about the size of a paper towel roll. Passive sodium heat pipes transfer reactor heat to high-efficiency Stirling engines, which convert the heat to electricity. …
“We threw everything we could at this reactor, in terms of nominal and off-normal operating scenarios and KRUSTY passed with flying colors,” said (chief reactor designer David) Poston.*
The [sup]239[/sup]Pu they have been using for RTGs such as are powering probes like the Voyagers and New Horizons is becoming hard to come by, and the output of the RTGs is fairly limited. This compact design looks quite promising.
Of course, ten years of power does seem a bit limited, given that the Voyagers are still sending back data after more than 40 years. It is not clear whether KRUSTYs can be refueled. But this is still a big advance for unmanned as well as manned exploration.