THE EFESTO PROJECT: FLEXIBLE TPS DESIGN AND TESTING FOR ADVANCED EUROPEAN RE-ENTRY SYSTEM BASED ON INFLATABLE HEAT SHIELDS

Kurzfassung

The European Union H2020 project EFESTO has been implemented with the main objective to improve the technology readiness level (TRL) of flexible inflatable heat shields for re-entry vehicles in Europe from 3 to 4 or 5. For this purpose, two reference missions with atmospheric entry to Earth and Mars were selected. Both missions were designed to make best use of the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) concept. Multidisciplinary design loops allowed prediction of the entry flight trajectory and identification of the aerothermodynamic environment on the exterior of the system. These results were the primary inputs to the design and testing of the Flexible Thermal Protection System (FTPS) layup and the underlying inflatable structure. This paper provides an insight into the efforts related to design, testing and numerical modelling of the FTPS for both applications. Advanced flexible materials were selected, some of which never had been considered in Europe before. These materials allow for a significant improvement upon previous design in system weight and maximum heat loads. Several multi-layer layups were developed for both applications, each of them allowing to keep the surface temperature below the material-specific upper limit. The most promising layups were selected for experimental simulation in DLR's arc-heated facilities LBK at flight relevant high-enthalpy conditions in realistic thermochemical environment. This testing covered both stagnation flow and tangential flow conditions in Mars and Earth atmospheres. Extensive numerical efforts were carried out to perform test rebuilding and allow cross-correlation between numerical and experimental simulations. The numerical models were calibrated with the wind tunnel data and further assisted in the analysis of the experimental results and the derivation of material specific properties and uncertainties. The project allowed to validate numerical models and simulations tools. This enables Europe to reliably design FTPS layups in future initiatives in the strategic field of re-entry solutions based on inflatable heat shields. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 821801.