Technologies for Rapid Affordable Hypersonic Flight Testing

The transition in boundary layer flows from laminar to transitional to turbulence has an important impact in hypersonic vehicle aerodynamics and aerothermodynamics. Ground tests of boundary layer transition are generally unsatisfactory due to the high noise levels of ground facilities compared to flight. Flight provides the best environment for measuring transition. However, current methods for measuring boundary layer transition are tedious, lack sufficient bandwidth, and are invasive in that the sensors often alter and disrupt the flow. Using commercial instrumentation in the Phase I program, we demonstrated the ability to use ultrasound to measure small, rapid temperature variations (<1 millisecond). Using multiple sensors, we showed how “hot spots” could be localized. In some cases it is possible to measure both temperature and heat flux. The sensors are attached to the interior surface of the aeroshell, thus do not alter the flow. In this program we develop ultrasonic-based instrumentation and test methods suitable for in-flight measurements of boundary layer transition. Using this instrumentation we show how arrays of sensors can be deployed to map the 2D temperature distribution. BENEFIT: Instrumentation developed in this program results in improved characterization methods useful for hypersonic flight. These tools speed development, improve understanding, and enhance validation of analytical models and hardware components for propulsion systems and aeroshells. Hypersonic flight is increasingly relevant in the aerospace industry, through advanced weapon systems and the expansion of public and private space endeavors including new launch vehicles, reusable launch systems, hybrid rockets, and low-cost, more efficient propulsion systems.