Einsatz moderner Software Techniken bei der Multidisziplinären Optimierung wiederverwendbarer Raumtransporter This thesis presents a multidisciplinary analysis tool RTSOPT for the simultaneous trajectory and system optimization of reusable launch vehicles. This software package has been devel oped at the Space Systems Institute University of Stuttgart over 20 years. In this work the tool has been revised fundamentally updated and improved both from the algorithmic and software point of view while maintaining the principal methodology model assumptions and the system dynamics for the flight simulation. The flexibility and performance increase achieved is dem onstrated by using this software package to perform system analyses of the partly reusable launch vehicle Hopper the central concept of the national technology program ASTRA. Hopper consists of a reusable unmanned and winged main stage and an expendable upper stage. The main stage is powered by three cryogenic Vulcain 3 engines a future version of the Ariane 5 main engine. The upper stage is powered by a cryogenic Vinci engine...