Aerothermal characterization of the CALLISTO vehicle during descent

Aerothermal loads are a design driving factor during launcher development as the thermal loads directly in- fluence TPS design and trajectory. 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 con- sider. For disposable launchers the heat flux due to base heating during ascent needs to be considered for aft thermal protections system (TPS) and structural design. With the current European long term strategy[1] moving towards a reusable first stage - aerothermal loads may significantly change. The CAL- LISTO vehicle is a flight demonstrator for future reusable launcher stages and their technologies. The program involves three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from CSG, Europe’s Spaceport. The challenge is to develop, all along the project, the skills of the partners. This know-how includes products and vehicle design, ground segment set up, and post-flight operations for vehicle recovery then reuse [2–5]. For the CALLISTO vehicle the highest heat fluxes are mainly due to heating from hot exhaust gases and heated air in proximity of the aft bay and on the exposed structures like legs and fins. The development of the plume extension is different for the considered re-entry, when compared to Falcon 9, or the studies presented in [6–8]. As shown by Dumont et al.[9] the plume remains relatively concentrated at the aft end of the vehi- cle due to high atmospheric pressure and only very low fractions of actual exhaust gas species enclosing the vehicle. In the current study we conducted computational fluid dynamics (CFD) studies in order to determine the aerothermal loads on the vehicle during descent through the landing approach corridor for both phase B and phase C aeroshapes. The database development for vehicle phase B and phase C are described in detail and analyzed for some of the most prominent interfaces. The final phase C database presented allows interpolation of interface heatfluxes for the entire flight domain (M, ρ) at varying angle of attack (between 180 deg and 160 deg). Further the sensitivity of the plume-vehicle interaction to angle of attack, chemistry, thrust vector deflection and engine throttling are investigated for a critical Mach number indicating further area of improvement for future databases