A New Ablative Heat Shield Sensor Suite

A new sensor suite is developed to measure performance of ablative thermal protection systems used in planetary entry vehicles for robotic and human exploration. The new sensor suite measures ablation of the thermal protection system under extreme heating encountered during planetary entry. The sensor technology is compatible with a variety of thermal protection materials, and is applicable over a wide range of entry conditions. The project has developed a reliable sensor that measures recession of an ablative thermal protection system used by a planetary entry vehicle. The sensor prototype has been built and tested in an arc jet facility in a flight relevant environment. The sensor suite includes optical sensors that sense existence of ultraviolet emission from high temperature gases in front of the vehicle.  As the surface of the thermal protection system recedes, it progressively exposes each sensor and provides timed locations of the moving ablation front. The sensor data does not rely on elaborate data analysis procedure which simplifies interpretation. The sensor suite can also be integrated in a sensor plug that can be readily embedded in a variety of thermal protection materials using proven installation procedures.Using data from the sensor, it is envisioned that the design of entry systems will significantly improve by reducing mass of the thermal protection system. The thermal protection system accounts for 5-50% of the entry vehicle mass, depending on the mission, which could be traded for increased efficiency and performance. It is also likely that existing entry vehicle architectures (build-to-print systems) would realize benefits by pushing the flight envelope to more extreme conditions based on flight data acquired by this sensor suite.