Speaker
Description
The rapid increase in space activities has led to a growing number of objects re-entering the Earth’s atmosphere, raising safety and sustainability concerns. Thus, reliable prediction of re-entry behaviour, including aerothermal loads, ablation, fragmentation, and survivability, depends strongly on accurate material characterisation. However, accurate data remain limited for materials exposed to high-temperature, reactive, and partially ionized environments, especially for metallic alloys.
For atmospheric re-entry, material characterisation requires a detailed understanding of thermodynamic behaviour, phase changes, oxidation mechanisms, and chemical composition evolution over a broad temperature range. Interaction with the atmosphere at several thousand kelvins leads to complex gaseous species and partially ionized plasma, strongly affecting heat transfer and ablation. Despite advances in thermochemical databases and modelling tools, data for multi-component metallic alloys remain sparse compared with classical thermal protection materials.
This work analyses the thermodynamic, transport, and compositional behaviour of metal–air mixtures to identify the main mechanisms governing material response during re-entry. Alloy Ti-6Al-4V is considered in the study. This material is widely used in aerospace applications, including structural components such as propellant tanks. It has high mechanical strength and good corrosion resistance. This makes its behaviour and survivability under re-entry conditions particularly relevant. Equilibrium thermochemical analysis is performed using the Mutation++ library. The metal-air interaction is analysed over various compositions, from metal-rich to air-dominated cases at atmospheric pressure and in the temperature range 500 – 6000 K.
The results reveal a transition from a Ti-dominated, metal-rich regime at low air fractions to chemically driven behaviour as air content increases. At 2500 – 4500 K, oxide formation becomes significant, mainly through TiO and TiO₂, while nitrides appear in smaller amounts. These species progressively dissociate at higher temperatures. The response is strongly non-linear, especially above 80% air, where small composition changes produce large thermodynamic effects. Equilibrium specific heat shows multiple peaks linked to oxidation, nitride formation, and dissociation, which sharpen and shift to lower temperatures with increasing air content. Dynamic viscosity varies smoothly, whereas thermal conductivity increases strongly at high temperatures due to reactive contributions. Above 5500 – 6000 K, all cases tend toward atomic species, indicating strongly dissociated regimes.
This work represents a first step toward building datasets for metallic and composite materials, supporting future data-driven and machine-learning approaches for re-entry modelling. Future work will focus on extending the analysis beyond equilibrium assumptions, incorporating gas-surface interactions, and expanding the database to a wider range of materials.