Through-Thickness Health Monitoring of Thermal Protection Systems

This program addresses the need to monitor surface recession, temperature, and through-thickness properties of thermal protection system (TPS) materials. These TPS materials have unique properties for shedding the heat generated under reentry conditions to protect the integrity of the spacecraft. However, ever-increasing mission demands require improved performance and a better understanding for modern heat shield structures. This can be accomplished with a noninvasive, nondestructive method that uses projected sensing fields through the thickness of the TPS material. Novel eddy current methods are proposed that incorporate innovative sensor array constructs, physics-based models, and multivariate inverse methods to nondestructively assess carbon-based TPS materials such as Phenolic Impregnated Carbon Ablator (PICA). The sensors can be mounted behind the TPS material or embedded within the TPS with sensing magnetic fields that are projected through the material. JENTEK?s physics-based methods for diagnostics of layered media using MWM-Array technologies have been demonstrated as a nondestructive evaluation (NDE) method for flexible and rigid ablative TPS materials for condition, orientation, and thickness assessment. These methods are commonly used for NDE, such as coating characterization, and have been extended to surface mounted sensing applications such as torque, fatigue, and heat treatment condition monitoring. This proposed Phase I will demonstrate the feasibility of these methods in an embedded sensor configuration for representative material layer configurations and a heating transient as well as investigate the adaptations required for full-scale testing and operation. JENTEK delivered the MWM-Array solution used by NASA KSC on the Space Shuttle leading edge to detect damage of the reinforced carbon-carbon (RCC) thermal protection tiles; thus JENTEK is well-positioned to deliver a novel method for health monitoring of TPS materials.