Integrated structural and thermal design of an entry vehicle aeroshell

Abstract

Preliminary designs of two different reusable entry vehicle aeroshells were developed and compared on the basis of total weight, projected cost, reliability, and manufacturability. The first design was performed in the "traditional" method; first, a graphite / epoxy composite structure was designed based on the primary load conditions. Next, a thermal protection system (TPS) was added to the exterior of the vehicle. The second design featured a structurally integrated TPS. This new approach utilized a sandwich panel design with the exterior facing comprised of a high temperature composite, the core comprised of a thermal insulator, and the interior facing comprised of graphite / epoxy. The finite element method (FEM) was used to analyze the stresses of two different aeroshell designs. It was determined that the traditional design outperformed the integrated design in .,almost every area. The exception to this was operational costs, which were not known as accurately as the other areas of comparison. However, it was noted that the relatively poor performance of the integrated design was due to the imposition of a minimum gage requirement on the facings and the assumed axial symmetry of the sandwich panel design. The necessary minimum gage requirement resulted in a design that was not sufficiently stressed to take advantage of the properties of the sandwich panel design. The assumed symmetry of the sandwich panel design requires that additional core material be included that is not present in the traditional asymmetric design.