Optical Diagnostics for Space Propulsion

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.