Accession Number:

ADA034204

Title:

Phase Distortion Due to Airflow over a Hemispherical Laser Turret,

Descriptive Note:

Corporate Author:

NAVAL POSTGRADUATE SCHOOL MONTEREY CALIF

Personal Author(s):

Report Date:

1976-09-01

Pagination or Media Count:

38.0

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.

Subject Categories:

  • Lasers and Masers
  • Space Navigation and Guidance
  • Optics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE