The aim of the activity is to build the aerothermodynamic model for the prediction of ablation and demisability of porous materials used in the manufacturing of spacecraft and launchers, like carbon winded composite fuel tanks and glass ceramic zerodur optics, in order to reduce the strong uncertainties associated to their thermal response during re-entry.

 

 

Recent investigations using plasma facilities for testing composite porous materials, have proven to not provide a clear trend with respect the thermal response of such materials. The results obtained in different facilities and also different countries (within Europe and outside Europe) are very contradictory. In addition, the numerical strategies used till now are also not confident. Current numerical strategies used for the simulation in atmospheric re-entry assume, implicitly, that the flow-material interactions are surface phenomena. Most of the tools either solve for the flow side or for the material, either separately or weakly coupled, using approximated boundary conditions at the interface. These strategies are not valid for porous materials, like carbon winded composites or glass ceramic materials. For those components, the hypothesis of a mere surface reaction is not valid. Due to their porosity, the fluid penetrates the surface and an important part of the reaction happen inside the material. In addition, the shape and porosity of the body are modified by the ablation and demisability process, which generate flow turbulences which in turn modify the transport of the reactants and reaction products, resulting in a very strong coupling between the flow and the ablation process.

Therefore, to understand the behaviour observed with porous materials during the plasma tests, here is proposed:

• to develop and calibrate carbon winded composite materials models, for the required ablation range and for models of resin pyrolysis and in-depth radiation.

• to perform computer simulations with a numerical code able to account for the integration of the porous/reactive flow model (as described above) with a shock capturing and LES technique; and to extend the method with a plasma constitutive model.

• to carry out dedicated experimental campaigns in a plasma facility free of dust, for the characterization of the ablation of carbon winded composite samples. The samples will be instrumented and tested for comparision and validation with the new models using the previously described code.

• to upgrade a multi-physics platform with the models above derived, to study the complex degradation of space debris composite materials along a re-entry trajectory, for different geometries and re-entry conditions.

The outcome of this work will allow to improve correlations for aerodynamic coefficients and heat fluxes in presence of porous materials, used in any trajectory simulation tools for the prediction of casualty risk.