SBIR-STTR Award

Lambda Instruments, Inc., in cooperation with Virginia Tech and Pratt & Whitney, propose to investigate the feasibility of developing ultra high-temperature, high-frequency sapphire optical fiber-based sensors for next generation hypersonic vehicle sensors and wind tunnel testing programs up to 3600 ºF. The capability to accurately measure the surface pressure, skin friction, and temperature gradient imposed on a body subjected to high speed flow is a vital first step toward improving the performance of future hypersonic vehicles. Although real-time determination of these parameters has been an on-going challenge since the early days of flight, only in the last 15 years has attention shifted to hypersonic conditions due to sensor advancements in miniaturization, sensitivity, and mounting techniques. Accurate measurements of aerodynamic heating is a major concern at hypersonic speeds. Temperature sensors used to monitor the thermal profile can also give insight into determining the peak in a shock interaction region or the boundary layer transition. Finally, current air-breathing hypersonic vehicles integrate airframe and engine. The entire fore body of a scramjet vehicle's underside, for example, may be used as an external inlet to provide flow at the perfect condition to the engine. Failure to accurately know or predict surface conditions can lead to engine failure or catastrophic vehicle structural failure.

Keywords:
Heat Flux Sensor, Fiber Bragg Grating, Sapphire Optical Fiber, Shear Stress, Skin Friction, Hypersonic Aircraft, Scramjet

The proposed optical fiber-based heat flux sensors possess many of the desired performance features for high-speed, high-temperature heat transfer studies for future Air Force hypersonic ground- and flight-test programs.  During Phase I, motivated by the demand for robust instrumentation for aerodynamic heat transfer studies, Lambda Instruments, Inc., in cooperation with the Aerospace Engineering Department at Virginia Tech and Vatell Corporation, successfully demonstrated the feasibility of a new optical fiber-based heat flux sensor.  The salient features of the prototype sensor include extremely high-temperature capability (approximately: 1273 K using silica fiber, 2323 K using sapphire fiber), small size (diameter < 0.02 ), and the potential for high-speed operation ( > 100 kHz).  Based on Phase I theoretical and experimental results, the development team strongly believes that the current and projected performance features of the prototype sensor make it a strong candidate for continued development in Phase II and eventual commercialization.

Benefit:
In addition to the current Air Force heat flux sensor application Lambda foresees significant commercial market possibilities for such devices in industry and fire research, meteorology and soil, broadband radiology, building physics, and material science.  Lambda proposes to investigate commercial development strategies for advanced high-temperature optical fiber heat flux sensors with Vatell Corporation. Lambda and Vatell envision a ready market for the proposed optical fiber-based heat flux sensors, primarily because of their potential to operate up to the 2000° F melting point of silica fiber and potential low cost.  

Keywords:
Heat Flux Sensor, Fiber Bragg Grating, Sapphire Optical Fiber, Shear Stress, Skin Friction, Hyperson