Getting to Mars is one challenge, but figuring out how to live there, even for a little while, is another massive hurdle.

But NASA is on the case. The organization is experimenting with a new power source—called the Kilopower reactor—that it says could provide safe, efficient, and plentiful energy needed for future robotic and human space exploration missions. Think of it as a tiny nuclear reactor available in two sizes: one kilowatt or 10 kilowatts.

This week, NASA provided an update on the project, which kicked off in 2015 as part of the Game Changing Development program. It’s led by the agency’s Glenn Research Center, in partnership with NASA’s Marshall Space Flight Center in Alabama, the Los Alamos National Laboratory, the Nevada National Security Site, and the Y-12 National Security Complex.

NASA and the U.S. Department of Energy (DOE) said initial tests on the prototype system, which began in November at the DOE’s Nevada National Security Site, have been successful.

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