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May 07, 2023

Printing spare parts in zero gravity

A metal 3D printer will be on board when the next crew heads for the

A metal 3D printer will be on board when the next crew heads for the International Space Station, ISS. In the long term, the printer will be used to make spare parts in space, but it will also provide important new knowledge that can lead to better utilization of resources on Earth.

From a space station hundreds of kilometers above the Earth's surface, there is—as DTU Professor and space instrument and technology expert John Leif Jørgensen points out—a long way to the workshop if you suddenly need a spare part that you do not have in stock. A metal 3D printer could prove to be the solution to precisely that challenge.

That is exactly why the people on the Huginn mission, headed by Danish astronaut Andreas Mogensen, will be testing a brand-new printer on the ISS. The printer has been developed for this purpose by European aircraft manufacturer Airbus for the European Space Agency, ESA. "Such a printer can produce exactly the bits you need up there," says John Leif Jørgensen.

The printer is equipped with a nozzle that spouts a stainless-steel wire. A laser beam melts the wire while the printer moves, creating the selected pattern and building the object for which the printer has been set.

"Technically it's just a small welding wire that you melt into place with a laser beam. But it will make it possible to produce complicated objects far away from a conventional production hall," says the professor.

The visit to ISS will give Airbus important insight into what changes may be needed to make the printer ready to manufacture spare parts in space on a larger scale.

As part of the project, the astronauts will print copies of a carefully designed 5-cm tall structure. Researchers at DTU have produced similar models on Earth. When the Huginn crew returns, the researchers will make accurate measurements of the two printed models to determine what differences there might exist between them.

"Everything made on Earth is affected by gravity. This means that physical effects may differ along and across the gravity. One such effect is that objects are often heated and cooled differently when processed creating internal tension, which in turn may cause materials to warp. The absence of gravity on ISS will minimize such built-in tensions in the printed figures," John Leif Jørgensen explains.

Mapping the differences between objects printed on Earth and in space will help scientists find better answers to fundamental questions about how metals behave under different thermal and mechanical conditions.

This deeper insight into materials physics can, for example, be used to reduce the margin of safety that manufacturers of metal objects use here on Earth—and thus reduce resource consumption, John Leif Jørgensen explains, "For example, parts for, e.g., aircraft are built substantially stronger than necessary because we don't know exactly how the materials behave. This obviously also applies to cars and bicycles, etc. Prospectively, you would be able to improve the efficacy in the use of many of the components and materials we use in society today if you can responsibly reduce the safety margin and go closer to the limit."

Two other DTU projects will be involved in the Huginn mission, scheduled to be lofted in August.

One of the projects will test virtual reality (VR) as a tool for stimulating mental well-being during a space mission. A consortium headed by DTU will deliver a VR system that can transport astronauts to peaceful places—such as a trickling stream in a forest—and thereby improve the astronauts' mental well-being on long missions.

It is a challenge to develop equipment that will function in space. The available VR systems make use of gravity to ensure that the universe presented to the user is oriented correctly and that it displays without images "flickering" when—for example—the astronauts turn their heads.

Consequently, it will take a lot of work to develop a system that functions just as well in zero gravity, thus avoiding making the astronauts motion sick. However, if it works as intended, it will open the doors for wider application of VR in space for practice, training, and entertainment.

In the second project, Andreas Mogensen will continue to capture the powerful lightning which emanates from thunderclouds and reaches up to a height of 50 kilometers—and which he captured on video during his first brief mission in 2015.

For the new mission, DTU Space will equip the Danish astronaut with a much better camera system capable of capturing up to 100,000 images per second with an unprecedented contrast of the amazing electrical activity, thus providing new insight into and perspectives on this phenomenon.

The many new images—together with data collected from the Danish space climate observatory ASIM, where DTU Space is responsible for the scientific management—will provide DTU researchers with more knowledge about how lightning affects the atmosphere's concentration of greenhouse gases and thereby Earth's climate.

Such knowledge will, for example, enable researchers to improve our climate models.

Provided by Technical University of Denmark