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Last week, the US Department of Energy and the space agency said their Kilopower Reactor Using Stirling Technology (Krusty) experiment could lead to “safe, efficient and plentiful” energy for manned or robotic exploration.
Four lightweight 10kW fission reactors could potentially power outposts on the Moon, Mars or beyond for at least 10 years using uranium-235 cores, passive sodium heat pipes and high-efficiency Stirling engines.
Beyond Earth, nuclear reactors may be the only feasible energy source, said aerospace engineer and British Interplanetary Society president Mark Hempsell.
“As long as nuclear reactors are used carefully, you essentially almost have to do it,” Hempsell told PE. Long periods of darkness, such as the Moon’s 14-day nights, mean other sources are not practical.
“In a lot of places in space, it is the only practical way, simply because if you’re away from the Sun you are away from sunlight, so you’re down to chemical systems… or you use nuclear.”
Current batteries are incapable of storing the energy required for running a space base for two weeks without input. And NASA is keen to explore shadowed craters on the lunar surface which are permanently in the dark, so crews could not use solar power.
The main fear with building miniature nuclear power stations in space would be transporting nuclear material from Earth, said Hempsell. “The obvious thing everyone gets worried about is launching, but they have found ways of storing nuclear material to survive explosions on board.”
Once in the vacuum of space, rogue nuclear material poses far less danger, the engineer added. “I don’t want it anywhere on Earth – but in space it is fine, because there are no fluids to spread it around.”
A “really, really high possibility of success” for maintaining the reactors’ structural integrity and controlling core heat is nonetheless vital, said Steve Jones, chief technology officer at the Nuclear Advanced Manufacturing Research Centre at the University of Sheffield.
The project is a great opportunity to use cutting-edge techniques being pioneered at the centre, he added. NASA is likely to use a “modular” construction technique, building as much as possible on Earth before completing the build on-site.
Powder metallurgy and hot isostatic pressing also hold promise for dealing with difficult materials such as beryllium, which is used for radiation shielding, said Jones. “The problem with machining beryllium is it is extremely volatile and we try not to machine any beryllium if we can help it. One way of avoiding that is to use near net-shape powder metallurgy.”
That technique uses extremely high pressure and temperature to compress materials into desired shapes. Additive manufacturing and so-called 4D printing – 3D printing that creates objects which change shape – could also be useful for creating stable reactors, said Jones.
The NASA and Department of Energy project is now developing mission concepts and reducing risks to prepare for a possible flight demonstration. A demonstration in 2020 could pave the way for the system’s adoption, including for missions that use ‘in situ’ resource utilisation to collect local fuels or other materials.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.