Phase distortion due to airflow over a hemispherical laser turret
Fuhs, Allen E.
Huhs, Susan E.
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Compressible flow over a laser turret creates a phase distortion. To gain insight to this problem a model of a hemispherical turret is developed. The flow field is obtained using a second order solution based on Janzen-Rayleigh expansion for the compressible potential flow equation. Contours of constant phase distortion were calculated; results at the critical Mach number are presented and discussed. It was found that the distortion at 0 degree elevation angle was equivalent to a positive lens whereas at 90 degrees the distortion is similar to a negative lens. At 45 degrees the main effect is beam tilting into the wind. For a ratio of beam radius to turret radius equal to 0.5, the focal length at beam elevation angle of 0 degrees is 16.5km. At beam elevation of 54 degrees the beam tilt was found to be 26.5 microradians. Cruise missiles with intercontinental ranges may use celestial navigation which requires precise measurement of angular location of stars. A distorted lens created by the ambient flow field causes an error in measurement. Knowledge of the external aerodynamics is important
NPS Report NumberNPS-69FU76101
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Fuhs, A.E.; Fuhs, S.E. (1980-04);Analytical models for optical phase distortion due to compressible flow over a laser turret are developed. Phase distortion is calculated for both blunt and small perturbation turrets. For the blunt turret, the Janzen-Rayleigh ...
Fuhs, Allen E. (Monterey, California. Naval Postgraduate School, 1980-03); NPS-67-80-003Using the optical system equation, the impact of a change in wavelength is determined. The rms phase variation at output aperture is critical and must be reduced by an amount equivalent to reduction in wavelength. If turret ...
Vanderplaats, G.N.; Fuhs, A.E.; Blaisdell, G.A. (1980-04);An analysis and computer program which optimizes laser turret geometry to obtain minimum phase distortion is described. Phase distortion due to compressible, inviscid flow over small perturbation laser turrets in subsonic ...