The UK Space Agency (UKSA) has signed a contract with global major industrial technology group Rolls-Royce to study future nuclear power options for space missions. This is the first such contract awarded by the UK and is also the first-ever contract between the UKSA and Rolls-Royce. The intent was to define and configure nuclear power solutions for space exploration over the coming decades. Rolls-Royce had considerable expertise in power (including nuclear power), propulsion and thermal management technologies and regarded space as a growing and challenging sector where such expertise would be invaluable.

“As we build back better from the pandemic, it is partnerships like this between business, industry and government that will help to create jobs and bring forward pioneering innovations that will advance UK spaceflight,” affirmed UK Science Minister Amanda Solloway. “Nuclear power presents transformative possibilities for space exploration and this innovative study with Rolls-Royce could help to propel our next generation of astronauts into space faster and for longer, significantly increasing our knowledge of the universe.”

“Space nuclear power and propulsion is a game-changing concept that could unblock future deep-space missions and take us to Mars and beyond,” highlighted UKSA chief executive Dr Graham Turnock. “This study will help us understand the exciting potential of atomic-powered spacecraft, and whether this nascent technology could help us travel further and faster through space than ever before.”

“We are excited to be working with the UK Space Agency on this pioneering project to define future nuclear power technologies for space,” averred Rolls-Royce Defence UK senior VP Dave Gordan. “We believe there is a real niche UK capability in this area and this initiative can build on the strong UK nuclear network and supply chain.”

Nuclear power solutions developed for space would also be applicable on Earth, the company pointed out. This was because emerging nuclear technologies had “multi-domain applicability”. The result would be leading-edge nuclear power capabilities which would be able to meet the needs of many markets and operators.

Although the use of nuclear energy in space, whether to power space stations, space colonies or crewed and uncrewed spacecraft, is not a new idea, it is a new development for the British space sector. This contract is another signal of the UK’s growing space ambitions, as nuclear power is just about the only feasible energy source for deep space missions, which require a power source that is very reliable and long-lasting.

The US space agency, the National Aeronautics and Space Administration (Nasa), has not only been long interested in nuclear power for space applications, but has been a leading user of nuclear power systems in space. Since 1961, Nasa has used more than 45 radioisotope thermoelectric generators (RTGs) to power more than 25 deep space probe and Mars lander missions. Perhaps most famously, RTGs power the Voyager 1 and Voyager 2 spacecraft, originally launched in 1977 to study the Solar System’s outer gas giant planets and their moons, but still operating today and now sailing through interstellar space, having left the Solar System in 2012 and 2018 respectively.

Nasa RTGs use the decay heat from Plutonium-238 to generate electricity by means of solid-state thermocouples; as the decay process produces lots of alpha particles but almost no gamma radiation, the shielding requirements are minimal. European Space Agency RTGs generally employ Americum-241, which produces far more gamma radiation than Plutonium-238, but at relatively low energies. The Soviet Union’s and Russia’s space agency has preferred to use nuclear fission power systems (FPS) in its space missions; these can be launched ‘cold’ and switched on once in space. Russia has used more than 30 FPS in space. (The US has only launched one FPS into space, in 1965.)

The most radical space nuclear power concept to date was ‘nuclear pulse propulsion’, which was seriously examined by the US from 1958 to 1965. This would have used small nuclear explosions to propel spacecraft. The project (which was not funded by Nasa, which lacked the necessary budget) was halted for political, not technical, reasons and the concept was never subjected to any meaningful real-world test.