In the Aure Mountains, researchers at the Fraunhofer Institute for Machine Tools and Molding Technology IWU, together with local craftsmen, have developed a Christmas rocket for the traditional “Wilhelm’s Nutcracker”. The incense rocket is powered by an incense cone whose heat “ignites” a special material in the separation chamber, opening the rocket’s cap and exposing the nutcracker inside.
“The mechanism relies on a component inside the rocket made of something called a shape memory alloy (SMA),” explains materials scientist Holger Kunz. “This functional material is made of half nickel and half titanium and can take two different forms depending on the temperature.” In a rocket, for example, a compressed spiral made of this material expands into a straight wire when heated, which then causes the rocket to open. The required 65°C can be easily achieved using an incense cone. After cooling, the material returns to its original shape.
Similar mechanisms are also possible with tubes and sheets made of metallic or other SMA. “In principle, all possible three-dimensional shapes can be shaped using materials,” Kunz says. These should only be “trained on” the material. These alloys aren’t just used for Christmas: Researchers are also developing materials for space travel, for example, with a component of SMA that unfolds a folded solar panel in space. Other applications can be found in kitchen appliances, in automobiles, in medicine or construction technology. There they can be used, for example, for coagulation stockings or special roller blinds that can use the heat of the sun to darken the facades in order to cool the rooms depending on the solar radiation.
“We’ve consistently received positive feedback about our Rocket Willie Christmas project,” says Koons. This is initially only a limited edition and is rather a smaller project for the researchers. However, the collaboration drew attention to both the materials science and craftsmen of Seiffen around Markus Füchtner and the creative center “Denkstatt Erzgebirge” around Wolfgang Braun, from which all parties benefited. We also want to work together on similar projects in the future.
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