For humans to ever colonize other worlds, power is needed. Power to get us there, but also power to keep us going while being there. As such, in anticipation of a sustainable return to the moon and the eventual arrival of humans on Mars, NASA is thinking about how to get sustainable energy on the ground. If solar panels can be useful, the space agency believes that it is also be necessary to bet on nuclear power. The agency is thus testing a mini-reactor.
So far, the space conquest has relied heavily on solar energy. Indeed, it is the Sun that feeds the ISS with electricity, for example, which allows a crew to live aboard for months. This energy used to heat and illuminate the pressurized modules. But there are also many uninhabited gears that have solar panels, such as the Hubble Space Telescope.
But in view of the ambitious exploration projects that NASA is planning, the Sun’s rays will not be very useful. There is not much sunlight in the shadow of a lunar crater, for example or at in places where where the sun does not shine for several days? Astronomers must therefore consider an alternative for those cases where the deployment of solar panels will not suffice.
This is exactly what the space agency does, with the support of the US National Nuclear Security Administration NNSA, whose primary goal is to strengthen national security through the military application of nuclear science. Together, they have successfully tested a device that relies on nuclear fission to provide energy for missions farther away, which can not rely solely on solar energy.
The prototype in question, called Kilopower Reactor Using Stirling Technology (KRUSTY), “is a small and lightweight fission energy system capable of providing up to 10 kilowatts of electrical power – enough to power many standard homes – on an ongoing basis for at least 10 years. Four Kilopower units would provide enough energy to build an outpost,” said NASA.
This technology would solve a massive problem if a base was to be installed on the moon, because the lunar nights last the equivalent of 14 terrestrial days. “When we start sending astronauts for long stays on the moon and other planets, this will require a new class of power that we have never needed before,” says the project leader.
Here, the device was built around a uranium 235 core whose dimensions are approaching a roll of paper towels. The installation itself is impressive, as can be seen with the photograph of the engineers working on KRUSTY, even if it is smaller than a conventional nuclear plant. In any case, it must be transportable on the Moon, Mars or elsewhere.
As far as the actual operation is concerned, the radiation from the core reaches the passive sodium heat pipes which then transfer the reactor heat to high efficiency Stirling engines. They are then responsible for converting heat into electricity. The test was divided into four phases, including a test that lasted 28 hours at full throttle and with all stages from ignition to extinction.
During the NASA and NNSA experiment, degraded operating scenarios were also tested, such as machine-generated power loss, heat pipe failure, or engine failure. According to the US Space Agency, despite these incidents, the system has continued to operate and provide electricity.