NASA Successfully Tests New Mini-Nuclear Fission Reactor, With Applications For Space Exploration

The National Aeronautic and Space Administration (NASA) recently announced that it has completed initial tests of a new miniaturized nuclear power system intended for missions in deep space. The device is referred to as Kilopower and it may one day bring power to bases established on the moon or Mars.

The Kilopower project cost about $20 million dollars, and it generates energy through the use of uranium. The uranium creates heat energy that could be used to power a variety of different devices, from spacecraft to water filtration units. The results of the Kilopower test were revealed during a conference held at the NASA Glenn Research Center in Ohio. The researchers who worked on the project stated that the Kilopower prototype (called KRUSTY – Kilopower Reactor Using Stirling Technology) exceeded all the expectations they had for it.

The Kilopower Prototype’s Performance

Kilopower uses nuclear fission to generate heat, which can generate electricity. Under the right conditions, the device could create constant energy for centuries, without using fossil fuels or relying on solar power. The reactor’s core utilizes enriched uranium, surrounded by a beryllium oxide reflector. The fission reaction that will convert the uranium into energy is kicked off with a rod of boron carbide. The heat the reaction creates is carried to power generators called Stirling converters. Any excess heat is vented out through a large radiator which sits on top of the device. The device is remarkably compact, being only around 2 meters or (6.5 feet ) tall.

Janet Kavandi, director of NASA’s Glenn Research Center said at the Ohio press conference that it’s critical to think about all the resources astronauts require to stay at a place and explore it. The Kilopower system could be incredibly important for expeditions into space where astronauts won’t be able to bring large amounts of supplies with them and will have to generate energy far from the Earth.

Said Kavandi:

As we move further into the solar system, there will come a point where carrying all the materials needed or attempting to resupply becomes hazardous. At this point, our explorers will need to be able to generate their own resources.

Kilopower could help the astronauts generate their own resources, powering tools and instruments that could create oxygen, water, and rocket fuel.

Photo: NASA, Public Domain

Initial tests of the Kilopower prototype were promising. A test done on March 21st ran a prototype for 28 hours, up to a temperature of around 800°C (1,470°F). Though the device only output between 1 – 4 kilowatts of power with an energy conversion efficiency of 35%, the research team says that when combined with their existing system its energy output could easily be scaled up to around 10 kilowatts of power. For reference, a 100 watt light bulb uses 0.1 kilowatt hours of energy every hour, so in 10 hours it would consume 1 kwh.

Future prototypes designed to accompany astronauts on missions to Mars or the Moon could produce around 40 kilowatts of power. According to a press release sent out by NASA, four 10-kilowatt Kilopower units would be needed to sufficiently power an outpost on Mars.

Safety And Energy Control Systems

According to Marc Gibson, lead engineer on the Kilopower project, the Kilopower reactor is a major milestone in the creation of nuclear reactors and for space exploration technology as a whole. Gibson explained that research on fission reactors for space exploration had been stunted from the 1970s to the early 2000s by long project time frames and high investment costs, leading to the cancellation of many projects.

“This is the first nuclear-powered operation of a new fission reactor concept in the U.S. in 40 years,” stated Gibson.

Unlike radioisotope thermoelectric generator (RTGs) which were used to power craft like Voyagers and Curiosity, the output of a fission reactor can be altered, meaning it can scale with energy demands. For instance, it could remain dormant during the launch of the rocket and the travel to its destination, turning on once the rocket has reached its destination. The ability to self-regulate not only increases the reactor’s safety, it also means that astronauts don’t have to sit there constantly monitoring the device. This would free them up to do other things.

The system is able to regulate itself because of an internal temperature control system that functions similarly to a thermostat. If the reactor in the device begins to overheat, the Stirling engines start drawing more energy from the uranium core, cooling the system. If the system starts to become too cool, the core contracts which traps more neutrons and increases the rate of fission.

Photo: NASA, Public Domain

NASA’s engineers say that they have done everything in their power to ensure that the reactor poses little to no risk to the public, following all safety protocols including the protocols established by the United Nations. The engineers say that there’s almost no chance the reactor could come on accidentally, even if an accident were to take place at launch. The reactor won’t even be turned on until the rocket has already left the Earth far behind.

The Kilopower team has also given consideration to safety at the site of the reactor on the Moon or Mars. NASA’s engineers will be creating containers intended to safely store used reactor fuel as it wouldn’t be practical to return the fuel to Earth. There’s no radioactive coolant in the reactor that could potentially contaminate the planet, and NASA is currently doing research on methods that would shield astronauts from any radiation that the reactor might emit during operation. These methods include building protective devices into the reactor itself and burying portions of the reactor in the surface of a planet/moon.

The Kilopower prototype differs in several ways from the units that may eventually be used in space flight, but the prototype was designed with the flight-ready units in mind, so the transition between the two units shouldn’t be very difficult. NASA will be moving onto flight tests next, though at the moment there aren’t definitive dates for those tests. While the Kilopower generator can be used on surface missions, it could also be utilized to provide energy to ion propulsion systems or be used in the proposed Lunar Orbital Platform-Gateway project.