Conceptual thermal response modeling, testing, and design of flexible heatshield insulation materials

Abstract

Flexible Thermal Protection Systems (FTPS) have been investigated to support many applications, including thermal protection of inflatable atmospheric entry vehicles. This flexible blanket is composed of a stack of material sheets, including heat rate resistant outer fabrics, heat load resistant insulation, and an air-tight gas barrier to prevent pressure leaks. This dissertation advances the state-of-the-art of thermal modeling, material property testing, and design of FTPS. In this investigation, a one-dimensional (1D) thermal response model is used to predict in-depth temperatures of FTPS layups during arc-jet ground testing. An extended inverse multi-parameter estimation methodology is developed to improve thermal model prediction accuracy. This method utilizes concepts from inverse heat transfer analysis, parameter estimation, and probabilistic analysis. Thermal response model input parameters are adjusted to minimize the error between temperature predictions and in-depth temperature measurements from arc-jet ground testing. Some FTPS insulators experience decomposition under extreme heating conditions, while others do not. In this investigation, a thermogravimetric analysis (TGA) experimental campaign was designed and executed to further characterize fibrous insulators that undergo decomposition. This material testing methodology was developed to obtain the approximate distribution of activation energy. Associated activation energies were inserted into corresponding thermal response models to improve temperature prediction accuracy. In this investigation, a simulation-based FTPS insulator design methodology is developed to obtain a final FTPS insulator configuration. This design process uses inputs such as candidate insulators, insulator material properties, and a nominal mission profile. Candidate insulators are designed efficiently using an improved thermal response model, providing FTPS insulator stackup configurations that satisfy mission requirements.