Speaker
Description
We present a loosely coupled radiative transfer analysis for superorbital Earth entry, targeting the strongly radiating shock layers encountered at entry velocities in the 18-25 km/s range characteristic of sample-return and high-energy return trajectories. At such velocities the post-shock gas reaches temperatures at which radiative heating becomes a leading contributor to the total wall heat flux, comparable to or exceeding the convective component. A self-consistent treatment of the radiation field is therefore required to predict the aerothermal environment and to inform the sizing of thermal protection systems.
The present work consists in the implementation of a loosely coupled radiative transfer capability within the SPARK framework. The flowfield is first converged with the SPARK Navier-Stokes solver, either assuming local thermodynamic equilibrium or using the two-temperature ($T/T_{ev}$) nonequilibrium model. The resulting thermodynamic state is passed to the SPARK Line-by-Line radiation module, which returns a divergence-of-flux source term that is fed back into the energy equation. Two distinct models are used to evaluate the radiative source term. In the first, the shock layer gas is assumed to be optically thin, meaning that none of the radiated energy is reabsorbed. In the second model, the flux divergence is computed by solving the radiative transfer equation line-by-line under the tangent slab approximation. In both cases an attempt is made to exploit the $T^4$ scaling of radiative emission for both increasing stability of the simulations, and improve the predictive capacity of the models while minimizing the necessary amount of radiative property computations.
This work was supported by the FCT - Fundação para a Ciência e Tecnologia, I.P., under projects UID/50010/2025 (\url{https://doi.org/10.54499/UID/50010/2025}), UID/PRR/50010/2025 (\url{https://doi.org/10.54499/UID/PRR/50010/2025}), UID/PRR2/50010/2025 (\url{https://doi.org/10.54499/UID/PRR2/50010/2025}) and LA/P/0061/2020 (\url{https://doi.org/10.54499/LA/P/0061/2020}).
Summary
We present the results for coupled hydrodynamic/radiative simulations of entry flows at superorbital velocities in the 18-25km/s range.