Uwe Ahrens graduated in Aerospace Engineering from Technical University Berlin. In 1989, he founded the medical company aap Implantate AG for which he acted as long-time CEO. Having established a patent basis for a rail-based airborne wind energy conversion technology, he founded NTS Energy Systems in 2007. In 2012, the company successfully demonstrated the core functionality on a linear test section. Foreword: Markus Hecht graduated in Mechanical Engineering at RWTH Aachen. After his PhD he worked in the railway industry in Switzerland until he became Professor for Rail vehicles at TU Berlin 1997. Main research topics of his group are energy efficiency and energy recovery.