Active thermal protection system against intense irradiation

Abstract

An active thermal insulation system for protecting a structure from intense incident radiation flux is considered. The system consists of a high-porosity semitransparent material through which a gas is transpired. A theoretical investigation is performed to study transient heat transfer by combined conduction, convection, and radiation in a layer of a semitransparent porous medium which is subjected to a high-intensity irradiation and injection of gas through the layer. Parametric calculations were performed and are reported in the paper. In the presence of gas injection through the porous layer, the temperature profile is totally different from that in the absence of injection, and the total heat flux through the layer vanishes within a small thickness. Drastic reduction in time to reach steady-state conditions is also achieved by the gas injection. The thickness of the porous layer and the radiation properties such as the single scattering albedo greatly affect the temperature distribution and the insulation performance.