ESA
If you're in any doubt about the progress being made in the additive manufacturing industry, know this: It is now possible to 3D print metal in space.
In 2024, a consortium of industry and academic partners successfully deployed the world's first metal 3D printer capable of operating within the microgravity conditions of the International Space Station (ISS). A small printed ‘S-curve’ line test marked the first milestone, followed by a series oftest tokens which have each since made their way back to the Earth’s surface, ready for analysis.
The project, named Metal3D, was established in 2017 when Airbus Defence and Space was awarded a contract by the European Space Agency (ESA) to pursue a giant leap forward for in-space manufacturing. In partnership with Cranfield University, AddUp and Highftech, the project set out to establish the impact of microgravity on both process and parts, and in the long-term, potentially, establish a new pathway to manufacturing metal parts for future missions, in space and on demand.
Designing a printer for space
Leading the development of the printer was Dr Wojciech Suder, Senior Lecturer in Laser Processing and Additive Manufacturing at Cranfield University's Welding and Additive Manufacturing Centre. Dr Suder and his team had previously studied the effect of gravity on liquids in computer simulations, but printing liquid metal in this environment, would be a first.
The key requirement was to develop a system that would use as little energy as possible, so Cranfield was essentially given the task of developing a heating device for a metal 3D printer, including the heat source, the feedstock, feedstock management, material selection, and monitoring system, all while remaining low cost, robust and energy efficient.
The team started with a trade-off study on paper, assessing energy consumption and potential hazards – you don't want to disturb other activities on the ISS – and theoretically exploring different processes, such as powder bed fusion, before landing on direct energy deposition (DED) as the most viable in terms of health and safety management – you really don’t want metal powder particles floating around space, either.
"Initially, the printer was supposed to be a big scientific and engineering test to see all the logistics, health and safety, how we would manage this sort of thing,” Dr Suder told TCT. “The big question was, from the logistics and engineering, can we manage health and safety? Could it be safely operated? Can astronauts do this sort of stuff? Because it’s all operated by them. Scientifically, the big question was, what's the effect of gravity on liquid metal? In the past there were some tests where astronauts were playing with liquids, floating droplets, but no one actually melted liquid metals at this level, which are very viscous. You need high temperatures to do it.”
Get your FREE print subscription to TCT Magazine.
Exhibit at the UK's definitive and most influential 3D printing and additive manufacturing event, TCT 3Sixty.
They carried out tests in terrestrial conditions, printing dog bone tests for tensile testing, each consisting of hundreds of layers.
“On earth we have gravity, which opposed the liquid metal trying to acquire a round shape, so the minimum surface energy of the system can be achieved. The gravity pulls it down a little bit to make it flatter,” Dr Suder explained. “The hotter metal is, the lower the surface tension, so you make it flatter and wider. If you don't have gravity, you don't have this force.”
These behaviours meant print parameters had to be operated in conditions where the anticipated effect of gravity is minimal, and the researchers ran several numerical simulations, essentially programming the printer so that the liquid metal would be deposited in micro gravity without the need for any compensation.
The printer is roughly the size of a microwave. It arrived disassembled onboard the ISS as part of the Cygnus NG-20 mission from Cape Canaveral in January 2024. The printed parts, which landed back on Earth in February, are now in the hands of researchers at the Materials and Electrical Components Laboratory at ESTEC for comparison with control samples printed on Earth to understand the impact of microgravity on the print process and part microstructure. A second sample has also been delivered to theTechnical University of Denmark, and results are expected to be published next year. While this first batch is focused on testing printing under microgravity conditions, the next batch aims to explore that potential with more complicated structures.
“The big goal is to be able to manufacture something in orbit and send it to further space,” Dr Suder said.“Taking any inventory from Earth takes a lot of fuel. If you imagine any complex habitat or spaceship requires a lot of spare parts, if you have to fly them all the time, it takes a lot of energy. It kind of makes it impossible for space exploration. If we could have, let's say, just feedstock material somewhere on the moon and you manufacture whatever you want and then send it, much less energy is required.”
Further impact
The ESA has described such research into in-space manufacturing as ‘crucial for self-sufficiency, allowing astronauts to manufacture essential parts, repair equipment and create tools on demand, without relying on costly resupply missions.’ But manufacturing in orbit at scale is still likely a couple of decades away from being a fully-fledged reality. Yet, there are gains to be made much closer than that, and much closer to home.
“You already have some components being manufactured in space and there is a benefit of lower gravity, for example, in drug use and other places where you can grow specific materials without the influence of gravity,” Dr Suder elaborated. “This [project] is another demonstration of remote manufacturing. This can be done in mines, underwater, it’s all the same kind of requirement. So, if we master something that can work autonomously in a remote, hostile environment, it's got multiple applications.”
But that doesn’t mean they’re not dreaming big about what this project could open up for the future of space manufacturing. The project has already sparked a lot of interest – including earning the Highly Commended spot for this year’s TCT Aerospace and Defence Award – and once established, Dr Suder believes the next phase will be delivering a fully automated process.
“This is the big challenge at the moment because these are very hostile environments,” Dr Suder explained. “Lots of radiation, the gravitational field is always continuously changing depending on the orbit level. But potentially we kind of imagine that this will be fully autonomous, operated by robots with little intervention by human. It's possible.”
This article originally appeared inside TCT Europe Edition Vol. 33 Issue 3. Subscribe here to receive your FREE print copy of TCT Magazine, delivered to your door six times a year.
