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Description
We present an analysis for the radiative heating of characteristic spacecraft shapes in representative entry trajectories into the Icy Giants Uranus and Neptune.
The current analysis develops upon the CFD analysis performed by Fluid Gravity Eng. (FGE) which has yielded a complete set of simulations for an axi-symmetric capsule flying at four representative trajectory points during an Uranus entry, and five representative points for a Neptune entry. The flow is also considered to be axi-symmetric (no angle of attack for the capsule), and accounts for the injection of ablation products into the flowfield boundary layer.
Entry velocities range between 17.5 and \SI{19.5}{\kilo\metre\per\second}. Nominally, for an entry at such velocity ranges in a pure \ce{H2}--\ce{He} atmosphere, radiation should be negligible, as attested by the experimental shock-tube results presented by Cruden \textit{et al.} \cite{Cruden:2017} which showed that shocked flows below \SI{25}{\kilo\metre\per\second} are expected to be radiationless. However, recent results by Coelho \cite{Coelho:2023} have highlighted that small concentrations of \ce{CH4} in Neptune (1.5\%) would yield dramatic increases of radiation, owing to the formation of C-containing species that are known to be strongly radiative at the representative post-shock temperatures in the \SI{5000}{\kelvin} range (atomic \ce{C}, and molecular \ce{C2} and \ce{CH}). Further, even in the absence of freestream carbon species, the presence of ablation products in the hot boundary layer might enhance radiation near the wall.
This warrants a detailed analysis of the radiative properties for those flows. This has been carried out considering the flowfields supplied by FGE, and preforming an analysis of these flowfields treating radiative emission/absorption/transfer in an uncoupled fashion. Flowfield conditions over four representative line of sights have been supplied, and radiative properties have been calculated using a specifically tailored radiative database, and deploying a simplified tangent-slab radiative transfer model.\
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