Mass Efficiency Considerations for Thermally Insulated Structural Skin of an Aerospace Vehicle

Abstract

An approximate equation was derived to predict the mass of insulation required to limit the maximum temperature reached by an insulated structure subjected to a transient heating pulse. In the course of the derivation, two figures of merit were identified. One figure of merit correlates to the effectiveness of the heat capacity of the underlying structural material in reducing the amount of required insulation. The second figure of merit provides an indicator of the mass efficiency of the insulator material. An iterative one-dimensional finite element analysis was used to size the external insulation required to protect the structure at a single location on the space shuttle orbiter and a reusable launch vehicle. Required insulation masses were calculated for a range of different materials for both structure and insulator. The required insulation masses calculated using the approximate equation were shown to typically agree with finite element results within 10–20% over the range of parameters studied. Finite element results closely followed the trends indicated by both figures of merit.