Speaker
Description
After more than two decades years of experimental and numerical simulation of the demise of materials and components during the entry flight, our knowledge on the phenomena involved in this destructive process and correct modelling thereof is still quite limited. There are many unknowns regarding the behaviour of the various materials and material categories and huge uncertainties. It is therefore necessary to make educated guesses in the modelling. The chosen simplifications and estimates can have an impact on the results of the numerical predictions and thus influence the results of the ground risk predictions and in consequence the design-for-demise measures and effort taken to make the risk compliant with the requirements.
We aim to contribute to the design-for-demise community by closing some of the gaps in the knowledge and understanding. These are the questions of whether alloys of one base metal can be considered to behave the same and the threshold that should be used for defining a metal to be demised.
In the frame of the ESA projects CHARDEM and DEPT, four aluminium alloys of dissimilar elemental composition underwent not only destructive entry flight testing in the arc heated facilities of DLR, but also vast thermophysical characterization. We use this data to show to which degree the alloy selection influences the demisability and demise behaviour and check which influence the selection of the alloy has on the behaviour.
It has been known for some time that the selection of a criterion for when a material can be considered demised in the numerical simulations is not easy. Earlier experimental simulations had shown diverse behaviour for the various metals and alloys and some materials differed quite a bit from the typical assumption that a material demises once it reaches melting temperatures. In the DEPT project, we investigated an aluminium alloy at different conditions by static and dynamic testing. In combination with older data, e.g. from the EU project ReDSHIFT, the results show an interesting correlation between mechanical loads and demise temperature.
In this talk, we present and discuss the results of the experimental investigations. We assess the impact of the two discussed simplifications on the demisability of materials and what this means for numerical simulations of the destructive entry flight. Best practices and recommendations for the DIVE guidelines are derived and presented.
