A unique experimental apparatus has been designed and constructed to characterize aero-optical distortions related to the turbulent flow conditions experienced by a windowed hypersonic vehicle. Using this apparatus, a series of imaging tests was conducted with a classical mixing/shear layer traveling at approximately 600 mIs. The experimental setup consisted of a collimated 0.84 mm laser diode point source that was passed through the flow field and imaged onto a CCD array. During a one second stable flow period, 92.5 frames of images were collected. Several runs were made with the lasr diode operating in both continuous and pulsed (40is duration) modes. These images were used to investigate several effects such as, image blur, jitter, and strehl loss. For long integration periods, the image experienced an average image blur circle size increase of approximately 24 times from the "wind-off" case. The pulsed runs showed an increase in jitter of approximately 36.4 j.trad. In addition, during continuous runs, a strehl ratio of approximately 0.0026 was observed. These and other preliminary results correlated well with theoretical predictions.

Date Published: 1 July 1991
PDF: 7 pages
Proc. SPIE 1486, Characterization, Propagation, and Simulation of Sources and Backgrounds, (1 July 1991); doi: 10.1117/12.45784

Published in SPIE Proceedings Vol. 1486:
Characterization, Propagation, and Simulation of Sources and Backgrounds
Wendell R. Watkins; Dieter Clement, Editor(s)