CFD Analysis of a Re-Usable First Stage in the Transonic Regime

Abstract: This paper presents drag coefficient and unsteady pressure loads for the RFZ model in the transonic regime. The RFZ model is an open-source, common research geometry for re-usable launchers and is used as a tool for the space community to benchmark aerodynamic and aerothermal results. This work addresses a gap in the current literature, where no detailed information on re-usable orbital class launchers during the transonic regime of the return-to-Earth phase of flight exists. Numerical simulations using steady-state Reynolds Averaged Navier Stokes, as well as unsteady improved Delayed Detached Eddy Simulations, have been completed. Results show that the trend for drag coefficient agrees well with published results for a cylinder placed in an axial flow, where drag is mostly attributed to the high pressure on the surface of the baseplate and the nozzles. Flow separation off the nozzles influences the local flow field experienced by the landing leg covers but predominantly affects the pressure loads recorded on the baseplate. Future work will extend this study to include the effect of a single active engine at Mach 0.75, indicative of the landing burn, as well as determine if unsteady loads in the vehicle base area pose any risk of structural excitation. Keywords: CFD, Aerodynamics, Reusable Launcher, Transonic, RANS, iDDES