Flow Control for Enhanced Sensor Beam/Directed-Energy (DE) Beam Quality

Conventional adaptive optic systems used on terrestrial telescopes are very slow, and not suitable for aero-optic corrections due to boundary layer turbulence on high-speed vehicles. For high-speed vehicles, the most critical need is to find effective and accurate methods for making these corrections, especially at transonic speeds where most applications reside. In this speed regime, currently available instrumentation can be used to obtain statistical measures of aero-optic distortion, but these measures have recently (Cicchiello and Jumper, 1997) been shown to underestimate the far-field effects of the distortion by orders of magnitude. It is therefore important to capture real-time wavefront data and calculate the far-field effects directly. To achieve this aim, high-speed measurements of wavefront distortion in two dimensions are needed, coupled with new high-speed adaptive optics. We propose to address the quantitative, time-resolved measurement of 2-D wavefront distortion caused by these fluctuations as a first step in finding a way to reduce or correct for wavefront distortion at high speeds. Specifically, we intend to: (a) develop a 2-D kHz rate wavefront analyzer for high subsonic Mach numbers; (b) make quantitative, real time measurements of wavefront distortion in high subsonic Mach number turbulent boundary layers; and (c) perform computer modeling of the measured wavefront distortion as a tool to study the design of adaptive optics suitable for this flow regime.