Modernization of Insulative Reusable Thermal Protection Systems (IRTPS)

Insulative thermal protection systems, such as Flexible Reusable Surface Insulation blankets and High Temperature Reusable Surface Insulation tiles, were developed for the Shuttle Orbiter to enable reuse of the vehicle for low-earth orbit missions. Since reusability is essential to many new industry launch and space vehicles, Shuttle-derived thermal protection materials (TPMs) are being sought for their flight proven performance. Alumina Enhanced Thermal Barrier (AETB) is the state-of-the-art tile material that was developed in the 90’s. AETB along with associated coatings, reaction cured glass (RCG) and Toughened Unipiece Fibrous Insulation (TUFI), are currently made by NASA using heritage raw materials derived from lifetime purchases. Finding viable replacements for raw materials that have changed in nature or are obsolete is important for continuation of these TPMs. In some cases, the use of modern raw materials has been shown to yield tile with reduced performance, most notably in mechanical properties. ​

In this work, the production of AETB will be discussed to better understand the process-structure-property relationships and for allowing use of these modern alternatives. A small-scale tile casting system was developed for rapid and efficient exploration of the manufacturing variables such raw material selection and pre-processing, casting process parameters, and billet firing protocols. An optical transmission defect characterization technique was implemented to correlate process variables to structure. Comparisons between TUFI/RCG coated AETB derived from heritage and modern raw materials will be shown including AHF arc jet test results completed under a collaboration with Stratolaunch.