Ablative Thermal Analysis Tool in ESATAN

Abstract

System level thermal analysis of space vehicles carrying ablative shields is usually performed by coupling the Thermal Mathematical Model (TMM) of the re-entry vehicle with the ablative bond line temperature resulting from thermo-ablative simulation. Such simulation is typically conducted by superimposing an ablative back wall condition. During these years, thanks also to the direct experience gained on ESA programs involving ablative shields like IXV, the need of a more strongly coupled thermal analysis has become higher in order to optimize both shield and thermal control designs. Being this numerical procedure involving different software, hence requiring the management of a complex iterative approach, the claim for a "one shot run" increased, this to remove time consuming and error prone iterations and improve model management/configuration control. In this frame TAS-I and Politecnico di Torino developed a new tool able to run directly intoESATAN the ablative analysis, allowing a full integration of ablative shield model with the host vehicle TMM. This paper describes the analytical model and 1D numerical scheme adopted and the verification and validation runs performed. Nomenclature β = degree of reaction m & = mass flow e = emissivity Ψ = convective flux reduction factor ρ = material/reactant density a = flow type coefficient B = ratio between the activation energy of the degradation reaction, E a , and the universal gas constant ℜ BB = blocking parameter C = thermal capacitance c = reactant weight coefficient c p = specific heat at constant pressure e = specific internal energy f = harmonic interpolation weighting parameter h = specific enthalpy k = pre-exponential factor n = reaction order 2 q = surface heat flux Q = constant recession enthalpy R = thermal resistance s = heat shield thickness S ij = surface between the cell i and the cell j T = temperature t = time V = cell volume x = in depth coordinate y = mass fraction Subscripts bl = boundary layer c = fully charred state cw = cold wall hw = hot wall i = index/counter mat = material rec = recovery condition ref = reference value rr = re-radiated v = virgin state w = external surface value