Aerodynamic Design of an Ariane 5 Reusable Booster Stage

Abstract

One of the partially reusable space transportation systems considered within the German future space launcher technology research program is the winged liquid fly-back booster (LFBB). The regarded system consists of two booster stages, which are attached to the expendable Ariane 5 core stage at an upgraded future technology level. The main area of interest of the presented aerodynamic study is the return flight after the staging procedure which dominates the layout of the LFBB. The proposed paper discusses the aerodynamic design activities performed at the Institute of Aerodynamics and Flow Technology of the German Aerospace Center (DLR). The layout of the LFBB is primarily based on Euler simulations using unstructured grids and the application of surface inclination methods. It covers the complete return trajectory from the staging Mach number of M = 6.5 down to the subsonic cruise flight at M = 0.5. Based on the numerical design studies a wind tunnel model is designed for force measurements in the DLR TMK facility. These measurements and selected Navier-Stokes calculations for wind tunnel as well as free flight conditions verify the accuracy of the design approach. First the approach for the definition of the required trimmed aerodynamic dataset is introduced. The discussion of the trim results for various LFBB configurations is then performed based on the numerically obtained flow fields. The results allow deeper insight into the influence of components like canards or a body flap on the aerodynamic behaviour of a LFBB. Additionally, extensive parameter studies enable to analyse the effects of e.g. the wing position, the airfoils of wing and canard, the Reynolds number or a windtunnel sting on the LFBB aerodynamics. Recollecting all the findings of the studies an enhanced LFBB configuration is introduced which allows an indifferent flight along the complete trajectory. During the definition of the vehicle the canard was the dominating parameter with view to the static margin. Additionally, the adaptation of the wing airfoil was a promising parameter. The final configuration has a very robust trim behaviour and the results additionally indicate a potential for further improvements.