Small Reactors - Energy Supply Solutions for Lunar Bases

Astronauts living on the Moon will require a significant amount of energy, but they cannot carry fuel supplies with them.

Like many other science fiction films, the television series Space: 1999, which aired in the 1970s, made a significant impact. The show depicts a nuclear explosion that tears the Moon from Earth’s orbit, sending Moonbase Alpha and the scientists stationed there on an exciting adventure through deep space.

Illustration of a power plant on the Moon. (Photo: NASA).

It is likely that this show left a strong impression on a young Elon Musk. In 2017, while envisioning SpaceX’s future Moon base plans, Musk named this base Alpha. Currently, SpaceX is collaborating with the National Aeronautics and Space Administration (NASA) to return humanity to the Moon’s surface as part of the Artemis program.

NASA and the U.S. Department of State have issued comprehensive guidelines for peaceful exploration of the Moon under the Artemis Accords. So far, 36 countries — including India, Japan, the UK, Canada, Australia, the United Arab Emirates, and South Korea — have joined.

China is also leading the race to build a Moon base. The International Lunar Research Station, established in 2021, currently includes cooperation from Russia, Belarus, Pakistan, Azerbaijan, Venezuela, Egypt, and South Africa.

Observers note that whichever alliance establishes the first Moon base will require a reliable energy source. Across the globe, many companies and space agencies have reached similar conclusions.

Simon Middleburgh from the Nuclear Futures Institute at Bangor University in Wales emphasizes: “The fact is, nuclear is the only option to power a Moon base.”

A day on the Moon is not 24 hours like on Earth; it lasts a month, specifically 29.5 days. In reality, there are two weeks of daylight followed by two weeks of darkness, with temperatures dropping to -130 degrees Celsius.

This is why the Apollo missions from 1969 to 1972 all occurred during the lunar day and near the Moon’s equator, when temperatures were manageable and prolonged sunlight could power scientific instruments and landers.

Illustration of the Space Flower Moon microreactor that could help power future Moon missions. (Photo: Rolls-Royce).

At the South Pole of the Moon, the most promising location for a base, certain spots receive sunlight for over 80% of the time. However, temperatures can drop further in permanently shadowed craters where frozen water may be found. This water is essential not only for helping astronauts survive but also for fuel production, as there are no gas or oil resources on the Moon.

“Nuclear is the only thing to consider on the Moon. We cannot bring fuel up there. Solar panels won’t work. Diesel generators won’t function, and old-style radioisotope thermoelectric generators are not large enough to generate power,” said Middleburgh.

In 1969, the first radioisotope thermoelectric generator was used on the Moon on Apollo 11, harnessing heat produced by the decay of radioactive plutonium-238 to keep scientific instruments operating at usable temperatures. On Apollo 12, this heat was converted into electricity to power a package of instruments, marking the first use of a nuclear reactor on the Moon, although not on a scale compared to Earth. This cylindrical generator measured just 45.7 x 40.6 cm.

A micro nuclear reactor would need to be lightweight and sturdy enough to travel 384,400 km and then be installed to operate under the extremely harsh conditions of the Moon’s surface, including invasive fine dust or a covering of rocky material.

In 2022, NASA contracted Lockheed Martin, Westinghouse, and IX, in collaboration with Intuitive Machines and X-Energy, to develop a nuclear reactor for the Moon.

The first phase was completed in February, showcasing designs for a reactor that could sustain a Moon base for at least a decade.

Illustration of a future Moon base. (Photo: Rolls-Royce).

Shatel Bhakta, head of the Moon architecture team at NASA’s Johnson Space Center, stated: “We are confident because we have used nuclear technology in previous space missions like Pioneer, Voyager, and Cassini, where these systems far exceeded their original design lifetimes.”

According to him, the harsh environment, the desire to minimize weight and volume, high reliability, and ensuring a continuous power supply to keep the crew safe are among the factors considered in the design of the reactor on the Moon’s surface. Additionally, due to the vast distance from Earth and communication delays, the system must be designed to operate autonomously, with minimal human intervention.

Meanwhile, in March, Russia’s Roscosmos space agency announced plans to build a nuclear reactor on the Moon with the China National Space Administration by 2035 to provide energy for a joint Moon base.

Yury Borisov, Director General of Roscosmos, told Russian state media that this base would be constructed “without the presence of humans.”

The UK Space Agency also announced a new $3.6 million grant for the design of a modular lunar nuclear reactor. For over 60 years, Rolls-Royce has quietly designed, built, and supported all nuclear reactors for the Royal Navy’s submarines.

Jake Thompson, chief engineer for Rolls-Royce’s New Nuclear program, stated: “We have a long tradition of delivering very compact nuclear reactors. Therefore, we are applying that capability to these truly exciting new areas such as space exploration.”

The Rolls-Royce microreactor program is currently in the ideation stage. Testing is being conducted on prototype components, with the aim of having a model ready to be sent to the Moon by 2029.

“These are fission-based reactor systems, so they will use low-enriched uranium. We have a pretty good idea of what these systems will look like and — especially for space — how much they will weigh. Each Rolls-Royce microreactor will generate 50-100 kW of power and operate for at least a decade,” said Thompson.

He noted that it depends on the architectural and infrastructural needs on the Moon’s surface, but there is a plan for a microgrid with a few reactors supplemented by solar power at the South Pole.

According to him, the microreactor will be roughly the size of a family car and weigh several tons. For a nuclear reactor, this size is incredibly small. However, for a space system, it remains relatively large. Miniaturized reactors are seen by many organizations as the “key” to a successful design, including the Nuclear Futures Institute, which is collaborating on the Rolls-Royce project.

He stated: “We will only deploy a system when it is safe in every aspect, including during launch, and the reactor is designed to only turn on when it actually touches the Moon’s surface. Before the reactor is activated, the nuclear fuel inside will be in an inert state. It is completely safe to handle and touch and does not become radioactive until the reactor is turned on.”

As part of the design process, engineers are also considering end-of-life processes for these microreactors.

Bhakta stated: “Once our Moon reactor mission is complete, we will shut it down, and the radiation levels will gradually decrease so that it can be safely accessed and transferred to long-term storage if desired.”

Funding and timelines to finalize these technologies are critical, but the application of microreactor designs on the Moon could extend to Earth — from flexible energy modules that could be much smaller than existing power plants to nuclear medicine.

Middleburgh, very optimistic about technology in space and on Earth, believes humanity has gone through many nuclear renaissance periods but needs the opportunity to demonstrate that nuclear energy is safe and carbon-free at the time of supply.

“These applications are incredible if we can show people that nuclear can be delivered on time, within budget, and can do interesting useful things — things that will save the world,” he said.