Progress in Aerodynamic Studies for CALLISTO - Reusable VTVL Launcher First Stage Demonstrator

Abstract

Reusability applied to launchers is expected to reduce costs for access to space and to increase the operational flexibility. DLR, CNES and JAXA are jointly developing a vertical take-off and landing (VTVL) reusable subscaled first stage demonstrator with the objective to improve knowledge in this field. With this vehicle, called CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations), DLR, CNES and JAXA want to acquire and demonstrate the capability to launch, land and relaunch a vehicle under conditions representative for the first stage of an operational launch vehicle. Furthermore, during CALLISTO demonstration flights, data will be gathered to improve knowledge on the operation of a reusable vehicle which will help to optimize the reusability capabilities of future launch systems [1-2]. The entire CALLISTO reference mission is complex and includes many flight phases: ascent, boost-back manoeuvre, descent and landing during which the aerodynamic shape and the thrust level are changing radically. For instance, the simulation of the retro-propulsion plume is of particular importance, as it has a major impact on the base pressure distribution and aerothermal loads. In order to refine the requirements in preparation for the product preliminary design review (Product PDR), extensive aerodynamic analyses and tests have been performed [3-4]. The key challenge is to create an extensive aerodynamic data base covering all the flight configurations and conditions which than can be used for 6-DoF flight dynamics simulation, considering the complex aerodynamic shape of the demonstrator with limited computing resources. Indeed, the aerodynamic performance plays a central role in the global performance of CALLISTO. The use of classic engineering aerodynamic prediction methods cannot provide the precision and reliability necessary for the estimation of the aerodynamic coefficients. It is necessary to use a combination of models and CFD methods of different complexity. Another important aspect is the estimation of the uncertainties, based on the comparison of results calculated by different CFD methods as well as experimental results obtained in wind tunnels [5-7]. This paper will describe the concept and structure of the aerodynamic data base as well as the methods used for the calculation. The main findings of the aerodynamic analysis and the progress made during the CALLISTO project will be presented.