Directed Energy Wind Tunnel Test Methodology

ABSTRACT: MZA partnered with the University of Notre Dame proposes to implement a series of mechanical and optical sensor measurements in a wind tunnel test section to isolate aero-optical disturbances from contaminating tunnel disturbances. We will develop a design for the necessary sensors and the number/location of these sensors on the tunnel observation windows. Particular attention will be given in our design to the sensor requirements for instrumenting tunnel test sections at AEDC which is extensible to other tunnel facilities. Mechanical modeling of tunnel window deformations will be conducted and validated through testing in Phase I at Notre Dame"s White Field test facility. Wavefront sensor measurements will be made of window deformations and additional tunnel-induced disturbances such as boundary layers, unintended shear layers, and temperature fluctuations in the tunnel free-stream flow will be quantified. Data processing for isolating aero-optical disturbances from tunnel contamination will be developed for the prototype measurement system. We will interface the measured tunnel disturbances to beam-train optical simulations in WaveTrain for assessing the suitability of the tunnel environment for proposed directed energy tests. Dr. Matthew Whiteley will be Principal Investigator for MZA and Professor Eric Jumper will be the Principal Scientist for Notre Dame. BENEFIT: The tunnel measurement system proposed here will allow AEDC and other wind tunnel facilities to isolate contaminating optical disturbances induced by the test section from aero-optical effects which are characteristic of laser directed energy systems and their associated beam director turrets/apertures. This system will improve the quality of aero-optical test data measured in subscale and full-scale wind tunnel tests for assessing performance limitations and operational envelopes of laser systems prior to costly aircraft integration and flight testing. Such a system will also help to identify sources of disturbances in the tunnel and suggest strategies for minimizing or eliminating these contaminants. Once tunnel disturbances are abated, additional testing such as real-time laser beam control tests can also be conducted in tunnels at AEDC. After proven successful for AEDC, the proposed measurement system, data processing, and optical modeling can be extended to other wind tunnels at government, industry, and academic facilities. The system may also be incorporated into a transportable Optical Diagnostic Range Simulator hardware used for testing laser systems in laboratory or hangar. The same product can be used in operational laser tests using a wind tunnel test section, becoming an integral part of the directed energy system developmental cycle.