Thermal Protection System for Reusable Launch Vehicles

Two contributors to the high cost of access to space are the use of disposable launch vehicles, and the extreme maintenance required by the U.S. Space Shuttle's thermal protection system (TPS), whose tiles can be easily damaged and thus, must be carefully inspected and frequently replaced between missions. However, high temperature materials currently under development for gas turbine compressors and hypersonic missiles may play a role in cutting the high cost associated with launch vehicles. Application of these high temperature materials to reusable launch vehicles (RLV) could lead to a simpler and less maintenance intensive TPS. This paper reevaluates the current state of the art materials with regards to their structural and thermal properties in an effort to determine if they hold the potential to lower the cost of space access. Relevant material properties and scenarios were combined and analyzed using a MATLAB based program which uses the diffusion equation to approximate heat transfer. This allows a designer to quantify the thermal transients and gradients during reentry. The program allows for a quick comparison of the proposed materials to the traditional shuttle design. The basic configuration of the proposed materials is similar to that of the TPS system currently used on the U.S. space shuttle, consisting of an outer non-structural layer for maximum thermal mitigation efficiency protecting an inner layer which provides structural strength and stiffness. The key difference lying in the idea that the application of high temperature materials allows for higher external and internal structure temperatures than traditionally allowed, reducing the demand on the TPS, and allowing for a shorter reentry duration.