Aerodynamic Effects on Airborne Optical Systems,
Abstract
A first-order determination of the effects of boundary flow of high-speed aircraft on the transmission of 0.2 micron to 20 micron radiation is presented. The four types of boundary flow considered are: main flow, shock wave, turbulent boundary layer (TBL), and separated flow. The potential-flow velocity field provides a means for computing wavefront aberration caused by curved density contours in the main-flow region. An example problem is worked out for a collimated beam emerging from a sphere. The density jump across a shock wave generally causes both beam refraction and beam degradation. The special case of refraction by a plane shock wave is computed. Estimates of the average modulation transfer function (MTF) for the TBL and separated flow are made from experimental data. From the wavefront aberration of main flow and the average MTF's for the TBL and separated flow, the effect of boundary flow on both propagating and imaging systems is analyzed. The effect is presented in terms of power density at the focus point for propagating systems and in terms of resolution for imaging systems. The effect of shock waves is not considered in the analysis because the only quantitative work in that area concerns beam direction only, not beam quality. In general boundary flow has only a slight effect on long wavelength (10.6 micron) radiation. The only exception is the effect of main flow at low latitude in which case power density at focus may drop to less than one percent of the diffraction limit. A similar power loss may be caused by both main flow and separated flow when the wavelength is short (o.55 micron). Only the TBL effect is not drastic.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 14, 1973
- Accession Number
- ADA122393
Entities
People
- D. J. Wolters
Organizations
- McDonnell Aircraft Corporation