Heat transfer in a multi-layered thermal protection system under aerodynamic heating

Abstract

Future generation reusable re-entry vehicles must be capable of sustaining consistent repeated aero-thermal loads without damage or deterioration. This means that such structures should be able to withstand high temperatures engendered by aero-thermal re-entry fluxes due to the establishment of a hypersonic regime over the body. Thermal Protection Systems (TPS) are used to maintain a reusable launch vehicle structural temperature within acceptable limits during re-entry flights; that is internal temperature should not be higher than the limit required by the internal structure. TPS are usually composed of several layers of different materials. Heat transfer through a multilayer insulation during atmospheric re-entry involves combined modes of heat transfer: heat conduction and radiation through the solid, heat radiation to the outer space etc. In the framework of the TPS design activities, a procedure based on one-dimensional analytical solutions of transient non-linear analysis has been developed in order to estimate the temperature variation with time and space of a multi-layered body subjected to aerodynamic heating inside a radiating space. Furthermore a semi-analytical procedure, able to take also into account non-linear thermal properties, has been conceived. Since internal temperature values of TPS of re-entry vehicles cannot exceed certain values, these procedures allow to quickly evaluate these temperature values and the preliminary size layer thicknesses without resorting to numerical solutions.