Book excerpt: Focusing on basic aspects of future reusable space transportation systems and covering overall design, aerodynamics, thermodynamics, flight dynamics, propulsion, materials, and structures, this report presents some of the most recent results obtained in these disciplines. The authors are members of three Collaborative Research Centers in Aachen, Munich and Stuttgart concerned with hypersonic vehicles. A major part of the research presented here deals with experimental and numerical aerodynamic topics ranging from low speed to hypersonic flow past the external configuration and through inlet and nozzle. Mathematicians and engineers jointly worked on aspects of flight mechanics like trajectory optimization, stability, control and flying qualities. Structural research and development was predominantly coupled to the needs for high temperature resistant structures for space vehicles.