Working in the biggest laboratory in the universe

Experimenting in 'microgravity' could result in better high-performance bio-medical and transport components

‘Why do we go to space?” Italian astronaut Paolo Nespoli posed the question to an audience in Dublin earlier this month as part of Science Week. The answers tumbled in: to explore, to learn, because it’s cool.

There are other, tangible benefits, too, according to Nespoli, describing how technologies developed for space applications have also helped to improve the efficiency of transport here on Earth.

Space offers a unique environment of microgravity or “weightlessness”. Yes, that means sometimes your spoon floats off as you are trying to eat dinner, notes Nespoli, who spent six months aboard the International Space Station. But it also means you can carry out experiments in a lack of gravity, and this can help to find out more about the effect gravity has on materials such as metals, and on our bodies on Earth.

Research in space and on the ground is now looking to get a better handle on those effects and how to overcome them. And the findings could lead to spin-off benefits such as lighter metals and plastics and maybe even better health as we age.

Solidifying alloys

So what’s the connection between gravity research and metal alloys in your car, or an implant in your knee? Gravity can affect the microscopic structure of the alloys as they solidify into shape, and that in turn affects how they perform, explains Dr David Browne, a senior lecturer at the school of mechanical and materials engineering in University College Dublin. “Metal is melted and poured into a mould, then it solidifies. And the progress of solidification essentially defines the grain structure in the casting,” he says.

“There is a push from industry to get a better handle on what is going on during alloy solidification so we can potentially control it better. The net effect could be lower-cost, lighter-weight components for transport applications primarily, and also increasingly high-performance components for biomedical applications.”

The issue is that on Earth the process of solidification is quite complicated to analyse, because as the molten alloy is solidifying, the liquid metal moves due to gravity, explains Dr Browne. He’s involved in an international study called CETSOL, which has been comparing how alloys solidify on Earth and in microgravity on the International Space Station.

“The alloys melt at over 600 degrees centigrade so they have to be encapsulated within ceramic crucibles. We don’t want them escaping and floating around,” he says. “And the astronauts switch them on before they go to bed because these very delicate experiments require that the astronauts not be moving around.”

The alloys solidify within a few hours, and when they come back to Earth the researchers chop them up and analyse their structure under the microscope.

“By removing the liquid motion, the process is much simpler and easier to understand,” says Dr Browne.

Researchers at UCD have already built a computer model of the process and one of the next steps will be to X-ray the alloys as they solidify in order to get a more dynamic picture of what is happening. UCD is leading a project to X-ray solidifying alloys aboard a “sounding rocket”, according to Dr Browne.