Speaker
Description
Material demise behaviour is critical to the casualty risk posed from re-entering space debris. However, the modelling of material demise in destructive re-entry tools, no matter how geometrically complex, tends to be very basic. The majority of tools model all materials as ‘equivalent metals’, where the assumption is that the material demise behaviour can be adequately captured using a melting point and a latent heat of fusion. This is clearly not the case for materials such as composites and glasses.
Some tools employ a 1D model for composite materials, based on the Charring Material Ablator (CMA) standard, but this can have a significant impact on runtime, and also requires specialist analysis to assess the pyrolysis and recession physics in order to build a suitable model.
In addition to these approaches, SAMj has employed a Heat Balance Integral (HBI) algorithm for some time. This reduces the one-dimensional heat conduction equation to a set of Ordinary Differential Equations (ODEs) which can be integrated in time only. As such, this provides a 0D approach which can account for conduction and ablative processes with no measurable impact on runtime.
Over time, the HBI approach has shown some robustness issues, particularly in the cooling portion of the trajectory. Therefore, this approach has been simplified, which provides increased stability, but is also able to capture the necessary material behaviour for accurate demise simulation. It has been applied successfully to the capturing of test data for metal (aluminium, titanium), composite (CFRP, GFRP) and glass (fused silica, Zerodur) materials, and can be extended to other material types where necessary.
