Reusability is expected to significantly lower launch costs if refurbishment and recovery costs can be kept low. To analyze and understand the impact of reusability on launch systems, the DLR is conducting studies of reusable space transportation configurations. In this context, a range of promising semi-reusable launch vehicles with a winged reusable first stage and either one or two expendable upper stages for an injection into a geostationary transfer orbit (GTO) were designed and investigated.
Different engine and propellant combinations, using either LOX-LH2 or LOX-LCH4, were studied in order to identify potentials and drawbacks of each combination. The winged first stage is recovered by the 'In-Air-Capturing' method which is currently studied in the framework of the Horizon 2020 funded project FALCon. A special focus is put onto the aerodynamic behavior of the winged stages. Since the stage performs a mostly aerodynamically controlled re-entry, transitioning from supersonic velocity of Mach 6-9 down to subsonic velocity, the vehicle has to be controllable throughout a vast range of different aerodynamic states. Therefore, a reference stage from the system analysis is selected and subjected to an investigation of dynamic behavior, controllability and stability along a reference trajectory. The insights from this analysis shall be used to re-evaluate the system design and determine implications on a system level
