Measurements of the gas state properties in hypersonic propulsion system research present unique problems demanding unconventional diagnostic measurement system design solutions. To resolve transient flowfield structures in these high-speed flows, the diagnostic instruments must have high spatial (on the order of 1 mm) and high temporal (on the order of nanoseconds) resolution. These requirements generally demand implementation of nonintrusive techniques. A review is given of nonintrusive techniques, which have been applied to flowfield diagnostics, including Planar Laser Induced Fluorescence (PLIF), Raman Spectrometry, Coherent Anti-Stokes Raman Spectrometry (CARS), and Rayleigh Scattering. A discussion is given of issues associated with the selection of equipment for PLIF and Raman systems, and of lessons learned in their application.
