Abstract:
Hypersonic flight systems are seeing significant renewed interest in recent years. The problem space presents a rich
combination of physics, where compressible fluid mechanics is coupled with non-equilibrium thermochemistry at high, MJ/kg
flight enthalpies. Sandia supports hypersonic system development with mod-sim and ground-test capabilities that are supported by co-located expertise in high-fidelity laser diagnostics. The focus of this talk is recent development of laser-diagnostic platforms for applications in hypersonic ground testing. In the bulk of the presentation, we will discuss coherent anti-Stokes Raman scattering (CARS) applications to multiple ground-test facilities. A wide variety of laser platforms featuring femtosecond- to nanosecond-duration laser pulses are used depending on ground-test requirements. Nanosecond laser pulses are applied to access extreme temperatures (T = 5000-7000 K) for materials testing efforts in an inductively coupled air plasma torch. Simultaneous temperature/pressure measurements in low-temperature (50-290 K) jets and Mach-8 wind-tunnel flows are demonstrated using ultrashort-pulse femtosecond CARS for hybrid time-/frequency domain detection. Picosecond N2 CARS thermometry at 100-kHz rates using a pulse-burst laser architecture is demonstrated Sandia’s free-piston-driven shock tube, where temperatures readily exceed 4000 K. The talk concludes with a summary of additional laser-diagnostic measurements
in Sandia facilities, including nitric-oxide detection using pulse-burst laser-induced fluorescence and high-speed absorption spectroscopy in high-enthalpy flows, and new rapid-scanning concepts for Doppler global velocimetry applied to Sandia’s hypersonic wind tunnel.

Bio:
Sean Kearney is a Distinguished Member of the Technical Staff in Sandia’s Engineering Sciences Center, where he has worked since 1999 to develop and apply laser-based diagnostics to a wide variety of national-security mission areas, including as nuclear safety, combustion, hypersonics, microsystems, and energetic materials. His current research interests are focused on burst-mode and ultrashort-pulse laser diagnostics applied to hypersonics, pyrotechnics, and explosive devices. He holds a Bachelor of Science degree in Mechanical Engineering from Clarkson University and Mechanical Engineering M.S. and Ph.D. degrees from the University of Illinois at Urbana-Champaign. Sean is active in the Optical Society of America (OSA) and is an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA), where he serves as incoming chair of AIAA’s Aerodynamic Measurement Technology (AMT) Technical Committee.

Host: Ellen Mazumdar