An x-ray recording of metal alloys being cast on Earth and then in microgravity. The crystals that form are where the metal starts to solidify.

The videos are part of an ESA experiment called XRMON that is a recurrent flyer on sounding rockets and is investigating how metal alloys form, searching to improve the materials we use in our everyday life.

On the 14th Maser sounding rocket campaign a 0.2-mm-thin piece of aluminium-copper alloy will be melted and then solidified in weightlessness. An X-ray beam will illuminate the metal sample and a camera will record it, like for a medical radiography. 

“We teach how metals solidify to students in university, and this experiment really allows us to see it happening, in weightlessness” says ESA’s science coordinator for this experiment Wim Sillekens.

Researchers are interested in how microstructures form as the metal solidifies.

“On Earth, the crystals in this alloy will rise in the liquid as they form – somewhat like how water ice crystals become ice cubes and will rise to the top of your drink”, continues Wim, “in weightlessness there is no buoyancy – in space an ice cube would stay suspended in your drink – allowing us to investigate the crystal-forming process more easily.”

This XRMON experiment ran on the Maser 12 campaign in 2012, and then on the Maser 13 campaign in 2015, but with different parameters allowing researchers to compare data and the cast alloy to further improve techniques.