Researchers have tested a small prototype of a nuclear-reactor engine design that could one day power deep-space exploration probes.
The proposed design is based on a Stirling engine – an engine first invented in the 19th century that uses hot pressurized gas to push a piston. It would use a 50-pound nuclear uranium battery to generate heat that is then carried to eight Stirling engines to produce about 500 watts of power.
Source: Wired. Read full article. (link)