Numerical rebuilding of Viking afterbody radiative heating with the DLR TAU code

Abstract

Axisymmetric flowfield and radiation transfer solutions are presented for three trajectory points of the Viking spacecraft in its descent through the Martian atmosphere. The flow adapted hybrid grid capability of the TAU code has been implemented to calculate the flowfield surrounding the vehicle with a particular emphasis on accurately capturing the relevant wake flow structures while minimising the grid size. Laminar and turbulent calculations are found to give substantially different solutions in the wake region. A Monte-Carlo based radiation transport algorithm incorporating opacity binning of the spectra is applied to solve for both the radiative heating at the surface and divergence throughout the flowfield. While the calculated convective heating rate on the fibreglass portion of the back shell is similar to that derived from a thermocouple on the Viking spacecraft, the convective heating on the aluminium portion of the back shell is approximately half the thermocoupled-derived rate. In contrast, the radiative heating rates on the backshell are 2 to 6 times higher than the thermocouple-derived heating rates. Possible explanations for the overprediction of radiative heating are investigated.