The Trauen site of the German Aerospace Center (DLR) is situated on Lüneburg Heath, close to the German military airport at Fassberg. This handy location, far from any settlements of note and yet close to many major conurbations, has been in use since 1935 for cutting-edge research. The work and experiments of Prof. Eugen Sänger, who oversaw the construction of the rocket-engine development centre in Trauen and developed breathtaking engines for rockets and guided missiles, aroused particular interest. One of his ground-breaking innovations is still used today in almost all rocket engines: jet cooling by propellant.