That’s one small step for nuclear reactors on the moon and Mars, and several giant leaps to go.
Eventually, the technology pioneered by NASA’s Kilopower project could provide the electricity required to keep the lights on at off-Earth outposts, and to turn space resources into the breathable air, water and rocket fuel required for those outposts.
“When we go to the moon, and eventually on to Mars, we are likely going to need large power sources and not rely on the sun,” Jim Reuter, NASA’s acting associate administrator for space technology, explained today during a news briefing at Glenn Research Center in Cleveland.
The first step is to confirm that the technology works, reliably and safely. And officials from NASA and the Department of Energy’s National Nuclear Security Administration, or NNSA, say they did that during a series of tests conducted between last November and March at NNSA’s Nevada National Security Site.
The key test came when the Kilopower team ran their test reactor through a 28-hour vacuum-chamber test that simulated a full power cycle, including startup, ramp-up, steady operation and shutdown. The power system — known as the Kilopower Reactor Using Stirling Technology, or KRUSTY — was put through additional tests to see how it dealt with multiple failures.
“We threw everything we could at this reactor, in terms of nominal and off-normal operating scenarios, and KRUSTY passed with flying colors,” David Poston, the chief reactor designer at NNSA’s Los Alamos National Laboratory, said in a news release.
The power for the system comes from a uranium-235 reactor core that’s about the size of a paper towel roll. Passive solar heat pipes transfer kilowatts’ worth of thermal energy from the core to high-efficiency Stirling engines that convert the heat to electricity.
“This is the first nuclear-powered operation of a new fission reactor concept in the U.S. in 40 years … not just for space, not just for NASA, but of any kind in the U.S.,” Poston said during today’s briefing.
The initial tests generated 1 kilowatt of electricity, but the power output can be scaled to provide up to 10 kilowatts continuously for at least 10 years. “That makes a nice building block as we go forward,” Reuter said. He anticipates that a lunar outpost will require up to 40 kilowatts, or the output of four Kilopower reactors.
The self-regulating system is designed to keep its core around a constant temperature of 800 degrees Celsius (1,472 degrees Fahrenheit) during operation, even in off-nominal conditions. That means the reactor can be safely operated on the moon or Mars, without having astronauts on duty nearby.
“They’re not going to be wanting to sit at a reactor control system all the time,” Poston said.
Over the next 18 months, NASA and NNSA will work out the regulatory and technical requirements for the next stage of testing, which is expected to build up to a flight demonstration.
Patrick McClure, Kilopower project lead at Los Alamos, said the certification procedure will be modeled on what’s currently used for NASA’s radioisotope thermoelectric generators. Such RTGs provide the electricity for robotic spacecraft including the Curiosity rover on Mars and the New Horizons probe that’s currently zooming beyond Pluto.
“We do believe we’ll make some possible changes to the process for reactors,” McClure told GeekWire.
McClure said the reactor is designed to start up nuclear fission only once it reaches its off-planet destination — a mode of operation that should pose “little to no risk to the public.”
NASA and NNSA pulled off the KRUSTY test project for less than $20 million, but team members said it was too early to predict how much it’ll cost to build a space-worthy version of the reactor. If all goes according to plan, NASA could deliver a 1,500-kilogram (3,300-pound) demonstration reactor onto the lunar surface in the mid-2020s on a medium-size commercial lander.
Poston said there could be earthly spin-offs for Kilopower technology.
“There are applications that are involved in deployable reactors for systems, whether it’s the military or a remote mining operation where you might want some amount of power. It could be economical there,” he said. “Trying to put power on the electrical grid … this is a long way from that. There is probably no application for commercial power, but there is for special uses for this reactor.”
For what it’s worth, small-scale nuclear power systems are currently under development for earthly applications at a number of startups —including TerraPower, a Seattle-area venture backed in part by Microsoft co-founder Bill Gates.