Kilopower (Credit: NASA)The US National Aeronautics and Space Administration (NASA) announced on 2 May that it had completed a full power test of its Kilopower reactor, which exceeded government expectations. 

In January, NASA, Los Alamos National Laboratory (LANL), and the Department of Energy announced that they had begun testing the small 10kWe Kilopower reactor for use on Mars, where it is expected to generate reliable power supply for long-term habitation. The reactor uses a small uranium-235 reactor core, and multiple high-power versions of the reactor could be used to power an extensive habitat. Kilopower could also be deployed on the moon to help search for resources in shadowed craters, according to Lee Mason, NASA’s Principal Technologist for power and energy storage.

The prototype reactor, designed and developed by NASA’s Glenn Research Centre in collaboration with NASA’s Marshall Space Flight Centre and LANL, was shipped from Cleveland to the Nevada National Security Site (NNSS) in late September 2017, where tests began in November. 

"This is the first new reactor not just for space and not just for NASA, but of any kind in the US in 40 years," David Poston, the project's chief designer at Los Alamos National Laboratory, told a press conference. "We demonstrated a concept that NASA can use right now. It's ready for a flight programme."

NASA’s targets include developing a huge rocket (the Space Launch System), setting up a space station near the moon, and sending missions to the lunar surface or even to Mars (in the 2030s). But this will require generating enough power to run systems vital to a long-term presence in space. "We are likely going to need large power sources not dependent on the sun, especially if we want to live off the land," said acting associate administrator of NASA's Space Technology Mission Directorate, James Reuter. "Our studies say that we would probably need up to 40 kilowatts of power on the moon, and then later on the surface of Mars." 

NASA already has small nuclear power supplies that enable ambitious robotic missions. These use the natural decay of plutonium-238 and provide only a few hundred watts of electrical power. Moreover, the plutonium is expensive, difficult to produce, and in short supply. This led NASA to develop Kilopower, which runs on fission. NASA says the reactor is designed to be safe, long-lasting, reliable, scalable, and energy-dense.

"This technology, we believe, will very likely be the most effective means to power human surface missions," Reuter said. The hope is that once Kilopower's capacity is scaled up, and the device becomes operational; astronauts could bury several units in the lunar or Martian soil, hook them up to their base, and let the system manage itself for ten years or more.

As an on-off switch, Kilopower uses a boron carbide rod, which absorbs neutrons. Inserting the rod into the fuel core shuts down the chain-reaction. Heat pipes filled with sodium metal feed heat to Stirling converters which drive a piston-like device to generate electricity. The sodium remains solid until melted by reactor heat.

To cool the converters a foldable, umbrella-like radiator made of titanium metal sits on top and radiates waste heat out into the air or space. In March, NASA tested the system in an experiment called Kilopower Reactor Using Stirling Technology (KRUSTY), which generated about 100 watts of electrical power. Poston said Kilopower could easily scale up to 10 kilowatts or even to megawatts. The researchers hope to establish a programme with NASA to build, test, and fly full-scale Kilopower units starting sometime in the next 18 months.

Photo: Researchers hope to set up a programme to build and fuly a full-scale Kilopower reactor