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Air power stands for altitude, speed and range. By using these characteristics in the 3rd dimension the air forces are capable of engaging targets flexibly, precisely, mostly independent of weather and time of the day as well as from a safe distance, if necessary. The unique features of air power are the exertion of control over the airspace as well as the linkage of altitude, speed, and range to complex capabilities such as rapid, world-wide deployment of personnel and materiel or a responsive and precise employment of weapons over long distances.The mission spectrum of air forces based upon this comprises a wide range of possibilities starting from aid and rescue missions to the demonstration of the political will up to a superior effect in the target - both within the scope of strategic air strikes which are directly aimed at the very foundation of an enemy and quick, mutual fire support on the tactical level as an immediate reaction to critical, unforeseeable development of the situation. (Europäische Sicherheit / SWP)

Superconducting generators (SCG) show the potential to reduce the head mass of large offshore wind turbines. By evaluating the availability and required cooling capacity in the temperatures range around 20 K, a Gifford-McMahon (GM) cryocooler among all the candidates was selected. The cold head of GM cryocooler is supposed to rotate together with the rotating superconducting coil. However, the scroll compressor of the GM cryocooler must stay stationary due to lubricating oil. As a consequence, a rotary helium union (RHU) utilizing Ferrofluidic® sealing technology was successfully developed to transfer helium gas between the rotating cold head and stationary helium compressor at ambient temperatures. It contains a high-pressure and low-pressure helium path with multiple ports, respectively. Besides the helium line, slip rings with optical fiber channels are also integrated into this RHU to transfer current and measurement signals. With promising preliminary test results, the RHU will be installed in a demonstrator of SCG and further performance investigation will be performed. ; This research is primarily supported by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 308793. Thanks for the technical support from Tom Black and Mark Granoff at Ferrotec.