Characterizing the Effects of Radiation During Dragonfly’s Titan Entry Using a Coupled Simulation Approach

During high-speed atmospheric entry, molecules can become excited due to the extreme temperatures, releasing large amounts of electromagnetic radiation as the electrons transition between energy states. This radiation creates a cooling effect in the shock layer, decreasing the stand-off distance of the shock wave, as well as increasing the heat flux to the vehicle surface as photons are absorbed by the wall. Due to these effects, it is important to determine under what conditions strong radiation is expected so that it can be accounted for in the design process. This paper focuses on the impact of radiation on NASA’s Dragonfly mission, which aims to deliver an exploratory rotorcraft to Saturn’s moon, Titan. Simulations are carried out for the Dragonfly capsule’s trajectory as it enters Titan’s atmosphere using a two-way coupling between US3D and MURP, where the former handles the flow physics and the latter the radiation transport. This coupling framework is leveraged to determine the significance of radiative heating on the afterbody and the necessary fidelity required to achieve a reasonable prediction. It is shown the wavelength range considered creates the largest impact on the solution. Accounting for non-Boltzmann radiation is shown to decrease the radiative heat flux, which is in line with previous studies.