An illustration of a Kilopower nuclear reactor on the moon. NASA is considering a flight test of that fission reactor technology, possibly flown on a lunar lander, in the mid-2020s. Credit: NASA

WASHINGTON — After a successful campaign of ground tests, NASA is considering performing a flight test of a small nuclear reactor, possibly on a lunar lander mission in the mid-2020s.

At a May 2 press conference at NASA’s Glenn Research Center in Cleveland, representatives of NASA and the Department of Energy’s National Nuclear Security Administration (NNSA) said a series of tests of the Kilopower nuclear reactor at the Nevada Test Site demonstrated its ability to safely generate 1 kilowatt, and ultimately as much as 10 kilowatts, of electrical power.

The tests, carried out between November and March under a project called Kilowatt Reactor Using Stirling Technology, or KRUSTY, culminated in a 28-hour test where the reactor was turned on, brought up to and operated at full power, and then shut down. NASA said the reactor worked as expected in those tests.

“We put the system through its paces,” said Marc Gibson, lead Kilopower engineer at Glenn, in a statement. “We understand the reactor very well, and this test proved that the system works the way we designed it to work. No matter what environment we expose it to, the reactor performs very well.”

The reactor consists of a solid core of uranium-235, regulated by a control rod. Heat from the radioactive decay of the uranium is transferred out of the core through passive sodium heat pipes. Stirling engines convert that heat into electricity, with radiators to reject excess heat.

The technology is of interest for NASA as a power source for future exploration missions to the moon and Mars. On the moon, such reactors could provide power during the two-week lunar night as well as permanently shadowed regions of craters at the poles where there is no sunlight. On Mars, the reactors can provide power at night and also during dust storms, when the effectiveness of solar panels is reduced.

“When we go to the moon and eventually on to Mars, we are likely going to need large power sources not dependent on the sun, especially if we want to live off the land,” said Jim Reuter, NASA’s acting associate administrator for space technology, at the press conference.

For NASA, the next step for Kilopower is likely a test of the reactor in space. “That’s our goal, to take what we’ve learned from this experiment and then go into a flight demonstration,” said Gibson. “We don’t foresee needing any more ground demonstrations on this particular system.”

The details of what that flight demonstration would be have yet to be determined, he said, and NASA hasn’t yet formally approved such a mission. Reuter said the next 18 months would be devoted to “pre-formulation activities” for such a test, including mission studies and risk mitigation work.

One possibility, he suggested, would be to fly the reactor on a mid-sized lunar lander, like what NASA is considering developing as part of its larger lunar exploration campaign. “Our vision for this is that it’s a great application to put it on the mid-sized lander in the mid-2020s timeframe,” he said. “It would be an enabler for a lot of the surface operations that we would want to do.”

NASA didn’t disclose what such a flight demonstration might cost. Reuter said that NASA has spent about $20 million over several years on the Kilopower effort to date.

“People thought it would cost billions of dollars to do these reactors. We showed we could design, build and test a reactor for less than $20 million.” said David Poston, chief reactor designer at NNSA’s Los Alamos National Laboratory. “NASA feels that we can develop this affordably and actually go do this.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...