Radiative Heating on the After-Body of Martian Entry Vehicles

Abstract

The radiative heat flux imparted on the after-body of vehicles entering the Martian atmosphere is simulated. The radiation is dominated by bands emitting in the midwave infrared. This mechanism traditionally has not been considered in the design of past Mars entry vehicles. However, with recent analysis showing that radiative heating can exceed convective heating on after-body surfaces, and with several upcoming and proposed missions to Mars potentially affected, an investigation of this radiation is warranted. This paper aims to quantify and improve understanding of the impact of radiation to aerothermal heating predictions for Mars entry. The tangent-slab approximation is shown to be overly conservative, by as much as 58%, for most of the backshell compared with using a full angular integration method. However, due to the complexity of the wake flow, it is also shown that tangent slab does not always represent an upper limit for radiative heating. Furthermore, analysis shows that it is not possible to provide a general correction factor to convert tangent-slab results to those obtained using the more rigorous full integration method. Radiative heating on the after-body often exceeds convective heating and therefore must be included in thermal protection system design for future missions.