An Introduction to Ablative Materials and High-Temperature Testing Protocols

Ablative materials are at the base of the entire aerospace industry because as sacrificial materials they allow the production of propulsion devices (such as liquid and solid rocket motors [SRMs]) or the protection of vehicles and probes during hypersonic flight through a planetary atmosphere. Some nonpolymeric materials have been successfully used as ablatives but, due to their versatility, polymeric ablative materials represent the widest family of sacrificial thermal protection system (TPS) materials. Thermal analysis such as differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and differential thermal analysis can establish the bases for a proper and comprehensive evaluation of the thermal response of composite TPS materials when exposed to high temperatures, enabling the modeling of the ablation process. However, the aforementioned protocols cannot properly simulate the real conditions of the hyperthermal environment in which TPS materials have to work. Other techniques such as the oxy-acetylene torch test or the simulated solid rocket motor allow to better study the response of ablative materials; these techniques can reproduce in a smaller scale the environmental conditions produced in an SRM. As a result, in light of the specific topic of Section 3 of this book, the purpose of this chapter is to provide readers with relevant generalities on ablative materials and related testing techniques, i.e., to introduce the proper tools to understand the scientific content and uniqueness of the other chapters of this section.