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After the National Aeronautics and Space Administration (NASA) partnered with the Defense Advanced Research Projects Agency (DARPA) earlier this week to develop a nuclear rocket engine, British aerospace firm Rolls-Royce also jumped into the fray. Rolls Royce is one of the world’s leading aeronautics and engine firms, with its products found in both military and civilian aircraft – alongside submarines and other machines.
The company also has a space segment, and it shared a rather tantalizing teaser on its social media yesterday showing a micro nuclear reactor. Nuclear propulsion these days, particularly for civilian and peaceful uses, is aiming to use High-Assay, Low-Enriched Uranium (HALEU) and it appears that Rolls-Royce’s engine will also utilize this fuel.
Rolls-Royce’s Tantalizing Reactor Render Leaves Mind Begging For More
The central message of the NASA and DARPA announcement was that the agencies have settled down on a safe fuel for using nuclear rocket engines. These engines already exist and are used in aircraft carriers and submarines – predominantly by the US military. However, the fuel used by these engines is highly radioactive and can also be used to make weapons. Naturally, this presents a complication for aerospace usage since the stakes are higher, and the missions are often further away from potential help should there be a problem.
Rolls-Royce is one company that is aiming at building nuclear reactors as well. It has been working on a small modular reactor (SMR) since 2015 and aims to bring it online by 2029. This reactor is part of the United Kingdom’s Energy Security Strategy, which aims to shift towards low-carbon energy sources by 2030. The brutal Russian invasion of Ukraine has played a decisive role in these developments, as the UK has been one of the hardest-hit countries due to the painful inflation resulting from Europe’s energy imbalance.
Each SMR is slated to generate at least 470 megawatts of electricity and cost a cool $3 billion initially. Impressively, the Rolls-Royce SMR is also the most potent SMR currently either launched or under licensing. Three have already finished production and are operational, according to the International Atomic Energy Agency (IAEA). Two of these are in Russia and the third is in China.

Rolls-Royce’s teaser shows what is potentially an extension of the SMR. The firm calls it a ‘Rolls-Royce Micro-Reactor’, and the power plant should be part of the company’s potential product portfolio to power human presence on the Moon. A Micro-Reactor isn’t the only product in Rolls-Royce’s portfolio, as the firm is also working on a ramjet engine and a power plant that aims to use naturally decaying radioactive material to generate power.
Additionally, Rolls-Royce is also working on a nuclear rocket engine for a two-stage rocket for launch, according to its head of innovation, Mr. Jake Thompson, who explains:
Right now over here at Rollys-Royce we have over 60 engineers and scientists working on these amazing technologies for space exploration. We’re currently working on the early concept design development and testing phase, both for our two-stage to orbit system and our nuclear systems. We’ve already built a small-scale prototype demonstrator of our space reactor, and by 2029, we’ll have a reactor ready to send to the Moon.
The company is also working with the UK Space Agency to explore the role of nuclear power in space exploration. Rolls-Royce’s testing is currently focused on ten heaters (potentially heat pipes) and the effect of power generation on their temperature, alongside investigating the effect on the overall engine head temperature. It also covers evaluating engine voltage and the corresponding engine power and system load. Additionally, it is also possible that the company is using a Stirling engine in its power system. NASA and the Los Alamos National Laboratory demonstrated a similar concept in 2012.
While nuclear engines sound like a novel concept these days, NASA has already conducted six successful tests so far. All of these took place in the 1960s and were part of the agency’s plans to explore Mars and the solar system. These tests used the Kiwi engine prototype and applied it to the Nuclear Engine Rocket Vehicle Application (NERVA) program. The NERVA test achieved a specific impulse that went as high as 701 seconds, with theoretical impulse in vacuum estimated even to cross 900 seconds. The tests were also extremely successful and ran without any problems surfacing.
In astronautics, specific impulse is the holy grail of engine design and performance. It essentially calculated the thrust (power) generated per unit of time by a unit of mass. This makes it a unit of efficiency, as engines that generate more thrust with less mass are more efficient and reduce the weight of the overall rocket. For comparison with the NERVA engine, the RS-25, responsible for powering the Space Shuttle and NASA’s Space Launch System (SLS) rocket, is one of the most efficient rocket engines in the world but has nearly half as much impulse as the NERVA – with a reading of 462 seconds. SpaceX’s Raptor 2, on the other hand, is aiming at 382 seconds.