Spallation Effects in TPS Models

During atmospheric entry, a hypersonic space vehicle is often slowed down by drag forces, which convert kinetic energy into heat. Thermal protection systems (TPS) help to keep this heat from harming the vehicle. These TPS are often made of an ablative material, which has a base made of a carbon fiber matrix. The process of ablation helps absorb the heat through mass removal of the material. However, the fibers that make up the carbon matrix are extremely thin, making them brittle. The process of spallation occurs when pieces of these fibers break from the matrix, resulting in many unwanted effects. Although understanding this process is important to accurately designing and analyzing the TPS, it is currently modeled using only an empirical parameter. However, results from recent arc-jet experiments provide an analyzed data set that gives further insight into this process—what causes it, the frequency of particles produced, and the resulting distribution of particle size. Additionally, utilizing the coupled computational fluid dynamics and material response solver known as KATS, the Gas Surface Interactions Lab is working to model individual spalled particles and their effects on the TPS. This code couples with the KATS solution to determine the chemical reactions of the particles with the surrounding flow field and the effects of individual particles on heating rates. However, it does not take into account how often or at what volume these particles are produced, or the material response to this particle production. Thus, this research seeks to develop the experimental results into a model that can be implemented into KATS to imitate spallation effects on the TPS. This model will allow the TPS to produce particles at a rate and size distribution relative to the given flow and sample conditions, as well as implement the resulting mass loss on the material.

This research seeks to develop the experimental results into a model that can be implemented into KATS to imitate spallation effects on the thermal protection systems (TPS). This model will allow the TPS to produce particles at a rate and size distribution relative to the given flow and sample conditions, as well as implement the resulting mass loss on the material.

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