A turbulent separated shear layer is investigated on a generic space launcher model in sub-, trans-, and supersonic free-stream conditions in order to characterize the fundamental physical phenomena that cause buffeting on a space launcher's afterbody during its ascent. The experimental work was carried out in the Trisonic Wind Tunnel Munich with particle image velocimetry and dynamic pressure measurements. The results show that the so-called step mode is mainly responsible for the high dynamic loads experienced on the reattachment surface aft of a backward-facing step. The loads are most predominant in transonic free-stream conditions. In supersonic free-stream conditions it is shown that only the subsonic part of the boundary layer has a statistical effect on the pressure fluctuations experienced on the reattachment surface. Subsequently, passive flow control is applied in order to reduce the dynamic loads in trans- and supersonic free-stream conditions. A load reduction of around $35\,\%$ is achieved with the most efficient geometry, next to a reduction of over $80\,\%$ in the mean reattachment length. This can be attributed to the imprinting of streamwise vorticity into the separated shear layer, which increases the turbulent mixing downstream of the step. The power spectral density distribution of the pressure fluctuations on the reattachment surface shows that the step mode is measurably diffused with the optimal flow control device. The successful control of the afterbody aerodynamics allows for the integration of longer nozzle extensions with a higher thrust capacity on a space launcher. Therefore, the interaction of an external flow with a Dual-Bell nozzle flow is investigated at last. At transonic conditions, the interaction of the external flow with the jet plume in sea level mode triggers screeching. In supersonic conditions, a Prandtl-Meyer expansion around the nozzle's lip decreases the external pressure in the vicinity of the nozzle exit by $58\,\%$. This causes the nozzle to operate in its altitude mode much earlier than predicted by current design methods, which consider the external pressure to define one of the most important nozzle design parameters, namely the nozzle pressure ratio. Therefore, a corrected formulation of the nozzle pressure ratio is introduced. Furthermore, an interaction between a supersonic external flow with the jet plume triggers the flip-flop phenomenon when the nozzle initially transitions. This yields a Dual-Bell nozzle designed to transition in supersonic flight unfeasible for the application on a space launcher. Future experiments need to verify that a nozzle designed to transition in transonic flight avoids interactions that lead to flip-flop.    «

A turbulent separated shear layer is investigated on a generic space launcher model in sub-, trans-, and supersonic free-stream conditions in order to characterize the fundamental physical phenomena that cause buffeting on a space launcher's afterbody during its ascent. The experimental work was carried out in the Trisonic Wind Tunnel Munich with particle image velocimetry and dynamic pressure measurements. The results show that the so-called step mode is mainly responsible for the high dynamic...    »