Design of a Robust, Multifunctional Thermal Protection System Incorporating Zero Expansion Lattices

On hypersonic vehicles flying within the atmosphere, viscous drag on acreage surfaces, even far from the hot leading edges, generates high temperatures, and, consequently, high thermal stresses and strains. This leads to two significant problems in the design of hypersonic airbreathers: insulation of the cool internal volume of the vehicle from the inclement exterior conditions, and reducing geometric changes in the vehicle surface to preserve aerodynamic shapes and to make it possible to connect the aeroshell to the cool structure within. A multifunctional sandwich structure incorporating very low density insulation as the core, with the structural stiffness provided by a hot face consisting of a low (or zero) thermal expansion lattice, fulfills these requirements. Here we analyze the feasibility of such a structure and discuss design and manufacturing issues, concentrating particularly on bonded joints in the lattice and connections between the hot face and the cool internal structure.