Acoustic Multiple Property Sensor System for Hypersonic Vehicle Thermal Protection System Ablation Measurements (AMPS-TPS)

As hypersonic systems continue to mature, technology that is critical to making hypersonic flight a reality is the aerospace vehicle’s thermal protection system (TPS).  Extensive research has focused on various methods of cooling the vehicle using various passive or active methods, as well as novel materials, that include CMC’s (Carbon Matrix Composites), refractory metals, and ablatives.  Regarding ablation technology, knowledge of the ablator’s recession rate provides the thermal/structural engineer with valuable information for designing the vehicle structure for two competing requirements: minimal weight and drag, and surviving the high enthalpy/high temperature environment of hypersonic flight.  Other important reasons for determining/measuring ablation recession rates are accurate evaluation of a vehicle’s profile drag. Drag is not only a function of vehicle geometry but also a function of vehicle boundary layer characteristics that are affected by the vehicle’s ablative chemically reacting characteristics, influencing surface conditions, thermodynamic and transport properties in the boundary layer as well as heat transfer rates to the vehicle surface.  The Navy performs many Submarine Launched Ballistic Missile (SLBM) flight tests. Some of these Navy SLBM test vehicles fly with an Extended Navy Test Bed (ENTB) telemetry unit. The ENTB takes sensor outputs from on-board devices and transmits them to a ground station.  The opportunity exists to develop an ablation rate sensor technology for carbon/carbon nosetips, to package the sensor technology suitable for the Navy nosetip application, and to provide an electronic interface unit so as to pass the ablation rate data to an on-board telemetry unit such as an ENTB.