Space alloy

Shape memory alloy couplings are being used to repair the external pipework of the propellant tanks on the European Space Agency’s XMM spacecraft.

Manufactured by California-based Aerofit Products, the CryoFit couplings are made from Tinel, a nickel-titanium alloy with shape memory characteristics. The inside diameter of the fittings is smaller than the outside diameter of the tubes on which they are used, but they are expanded at cryogenic temperatures so that the inside diameter becomes greater. Stored in liquid Nitrogen, the fittings are placed over a tube end, and as they warm, they shrink down on to the tube with a high radial force and form a permanent metal to metal seal.