Implementation of Surface Radiation and Fluid-Structure Thermal Coupling in Atmospheric Reentry

During atmospheric reentry, radiative heating is one of the most important component of the total heat flux. In this paper, we investigate how the thermal radiation coming from the postshock region interacts with the spacecraft structure. A model that takes into account the radiation reflected by the surface is developed and implemented in a solid solver. A partitioned algorithm performs the coupling between the fluid and the solid thermal fields. Numerical simulation of a hollow cone head and a deployed flap region shows the effects of the radiative cooling and the significance of the surface radiation. 1. Introduction When a space vehicle travels through the different layers of the atmosphere in the reentry phase, its most external part is subject to extreme thermal conditions. A thermal protection system (TPS) is hence installed to insulate the vehicle’s parts or its contents from high temperatures and heat fluxes. A significant amount of the total heat flux reaching the vehicle is due to the radiation coming from the postshock hot plasma [1]. Numerical simulations are one of the most widely used tools to design the TPS, and a detailed mathematical model allows to reduce margins in the sizing. A higher level of accuracy is obtained by including in the physical model the thermal response of the solid to the heat fluxes, through a coupled approach. In the latter, atmosphere gases and the spacecraft structure form two distinct systems that interact through the external surface of the TPS, and through which energy exchanges occur. To enhance the thermal control, the material of the TPS is chosen such that it reflects part of the incident radiation. However, in particular geometric configurations such as cavities, the reflected radiation can reach other surfaces of the vehicle structure. This paper exposes the development and the implementation of an implicit method for the calculation of surface radiation. This solution of the structure problem is coupled to the fluid flow through a partitioned algorithm. Some space vehicles can be equipped with side flaps that are used to steer the vehicle. The deployed configuration of these flaps presents a gap, and radiative effects in this area are of major interest [2]. We will apply the methods developed in the first part to this particular geometry, and the effects of surface-to-surface radiation will be investigated. 2. Numerical Tools During atmospheric reentry, the hot gas around the spacecraft transfers energy fluxes to the structure through the fluid-structure interface. The solid then reacts, with part of