One method for measurement of temperatures and densities in rarefied flow is laser-induced fluorescence (LIF) spectroscopy, 1 "" 3 which is applied to the re-entry simulation of Hermes, Sanger, and the Shuttle in wind tunnels. The strong nonequilibrium of rotational and vibrational temperature is typical of hypersonic wind tunnels due to the rapid expansion in Laval nozzles or freejets. LIF excitation spectra of nitric oxide, NO, were measured in a hot supersonic freejet expansion in the vacuum wind tunnel at…
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