An in-situ ablation recession rate sensor for carbon/carbon ablatives based on commercial ultra-miniature thermocouples

In this research, a breaking-wire like recession sensor based on commercial, ultra-fine thermocouples (250 μm diameter) was designed and tested. The proposed approach uses low cost, commercially available raw materials and processing techniques. A series of thermocouples (TCs) are positioned at a well established depth from the surface. When the temperature rises above the melting point of the Seebeck junction, the TC would break working as a position marker. The proposed ablation recession sensor was tested on carbon/carbon composites (CCCs) under a severe hyperthermal environment. Two types of CCCs with different densities were considered. Two different layouts were tested: 4- and 8-levels configuration. The obtained data showed that the proposed approach provide an accurate estimation of the ablation rate. Due to the uniqueness of the proposed sensing technique, it can be applied both on TPSs of spacecraft as well as on nozzle throats of solid rocket motors.