Phase distortion due to airflow over a hemispherical laser turret
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Authors
Fuhs, Allen E.
Huhs, Susan E.
Subjects
Advisors
Date of Issue
1976-09
Date
1976-09
Publisher
Monterey, California. Naval Postgraduate School
Language
eng
Abstract
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
Type
Technical Report
Description
Series/Report No
Department
Mechanical Engineering
Identifiers
NPS Report Number
NPS-69FU76101
Sponsors
Funder
Format
Citation
Distribution Statement
Approved for public release; distribution is unlimited.