In Situ Ablation Recession and Thermal Sensor for Thermal Protection Systems

In this research, a break-wire-like ablation recession and thermal sensor based on commercial, affordable thermocouples was designed, fabricated, and tested. The objective of this paper was to demonstrate the capability of this technique to provide real-time measurement of in-depth temperature and recession rates. The in situ ablation recession and thermal sensors were assembled on ablatives ranging from low to high densities (similar to 0.30-1.45 g/cc). The different types of ablatives adapted for this study were phenolic impregnated carbon ablator, AVCOAT, carbon/phenolic, and carbon/carbon composites. These ablation recession and thermal sensors were tested under an oxidative hyperthermal environment at a heat flux in the range of similar to 900-1000 W/cm(2) created by an oxyacetylene test bed. The results were very promising, demonstrating that the proposed approach can provide accurate recession rate data of a variety of ablatives. The sensing technology developed is very versatile and can be applied to the thermal protection systems of spacecraft, and can also be exploited on rocket nozzles. The key features of this sensor system are the use of inexpensive, commercially available thermocouples and industry-standard drilling techniques demonstrated on different ablatives.