Phase distortion due to airflow over a hemispherical laser turret
By: by A.E. Fuhs and S.E. Fuhs
Contributors: Huhs, Susan E.; Naval Postgraduate School (U.S.)
Publisher: Naval Postgraduate School
Published: 1976
Place of publication: Monterey, Calif
Language: eng
Number of pages: 35
Subjects: Aerodynamics; Lasers; Guided missiles
Description: 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.
Notes: Title from cover.

"September 1976"--Cover.

"NPS-69FU76101"--Cover.

Includes bibliographical references (p. 31).

"Approved for public release; distribution unlimited"--Cover.

Technical report; 1976.