Active Flow Control of Turbulence for Airborne Directed Energy Weapons

"The application of airborne Directed Energy (DE) weapons is under consideration for the Joint Strike Fighter (JSF) and Unmanned Combat Air Vehicles (UCAV). Intense turbulence is encountered along the beam propagation path in the aircraft nearfield, e.g.boundary layer, free shear layer, or wake. Flowfield turbulence creates a highly non-uniform and time-varying, three-dimensional, fluctuating density field, causing a propagating optical wavefront to incur phase delays and become aberrated. Aero-opticalwave-front errors produce beam spreading in high-energy laser weapon beams, which drastically reduces target irradiance and lethality for DE weapons and impairs laser-guided bomb accuracy. Optical degradation, and compensation by adaptive optics, iscompounded by the broad spectrum of turbulence frequencies, which can exceed 10 kHz for typical fighter flowfields. The Phase II program will provide sub-scale demonstration of beam performance improvement by implementing high-frequency flow control, usingnovel actuators. High-resolution numerical simulations and novel optical diagnostics will provide insight into the physics underlying beam attenuation and remediation. Scaling laws will be developed and flow control effectiveness demonstrated. The Phase IIresearch paves the path for implementation of high frequency, active flow control of turbulence around full-scale DE weapons, with the goal of reducing the demand upon the adaptive compensat