Fission power plant for larger solar system probes. Bob Zimmerman

May 05, 02:00 AM


(Photo: Cassini-Huygens assembly


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Fission power plant for larger solar system probes. Bob Zimmerman

NASA has successfully completed a full test of a new small fission power plant that it hopes to use in future space missions.

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.

According to David Poston, the chief reactor designer at NNSA’s Los Alamos National Laboratory, the purpose of the recent experiment in Nevada was two-fold: to demonstrate that the system can create electricity with fission power, and to show the system is stable and safe no matter what environment it encounters. “We threw everything we could at this reactor, in terms of nominal and off-normal operating scenarios and KRUSTY passed with flying colors,” said Poston.

The Kilopower team conducted the experiment in four phases. The first two phases, conducted without power, confirmed that each component of the system behaved as expected. During the third phase, the team increased power to heat the core incrementally before moving on to the final phase. The experiment culminated with a 28-hour, full-power test that simulated a mission, including reactor startup, ramp to full power, steady operation and shutdown.

Throughout the experiment, the team simulated power reduction, failed engines and failed heat pipes, showing that the system could continue to operate and successfully handle multiple failures.

This power plant appears similar in concept to the fission RTG nuclear fuel systems that have been used routinely for decades on unmanned planetary probes such as the two Voyager spacecraft, New Horizons, and on Curiosity. This new system however provides significantly more power, as much as ten kilowatts compared to the approximate two hundred watts provided by RTGs.

Such a system will be essential for future bases on both Mars and the Moon, where solar power is not the best option. I should also add that such a system might possibly have applications here on Earth. Developed properly, it could provide a practical power source for out-of-the-way locations not on the grid. If made cheap enough, it might also provide electrical customers a cheaper and competitive alternative that will allow them to remove themselves from the grid entirely.