Aerothermal characterization of the CALLISTO vehicle during descent

Abstract

Aerothermal loads are a design driving factor during launcher development as the thermal loads directly influence thermal protection system (TPS) design and successively the possible flight trajectory and mission profiles. Recent developments in reusable launch vehicles (RLV) (e.g. SpaceX, Blue Origin) have added the dimension of refurbishment to the challenges the thermal design must consider. With the current European launcher roadmap moving towards a reusable first stage aerothermal loads may significantly change. The CALLISTO vehicle is a flight demonstrator for future reusable launcher stages and their technologies developed by a tri-national consortium and planned to fly in 2025. For this vehicle the highest heat fluxes are mainly due to heating from hot exhaust gases and heated air in the proximity of the aft bay and on the exposed structures like legs and fins. In the presented study we conducted computational fluid dynamics (CFD) studies to determine the aerothermal loads on the vehicle during descent through the landing approach corridor for both phase B and phase C aeroshapes. A defining difference to previous aerothermal databases (ATD) is that the CALLISTO demonstrator is planned to execute a series of test flights with different energy levels, as well as a final demo flight. This leads to an large parameter space the final aerothermal database needs to cover. The database development is described in detail and analysed for integral and local loads, as well as interpolation uncertainties. The final phase C database allows interpolation of interface heatfluxes for the entire flight domain (Mach number, density at varying angle of attack (AoA). Further the sensitivity of the plume-vehicle interaction to angle of attack, chemistry, thrust vector control (TVC) and engine throttling are investigated for a critical Mach number indicating further areas of improvement for future databases.