Arnold Center uses wind tunnel to test directed energy system

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The Aerodynamics Branch of the Arnold Engineering Development Complex at Arnold Air Force Base, Tenn., Helps the Air Force take directed energy systems in flight.

DE systems use high energy lasers or microwaves to degrade or destroy threats and targets.

“There is a growing interest in directed energy systems within the DOD for many purposes, particularly the defense of our systems and our staff,” said Dr Rich Roberts, head of the store separation section. of the aerodynamic branch. “There are a number of systems in use and under development in the DOD. Integrating DE systems on airplanes has obvious advantages, but also creates challenges, especially at higher speeds. “

During flight, an airplane creates shock waves in the air and other aero-optical flow disturbances that can affect the beam quality and efficiency of an ED system. Wind tunnel testing allows test engineers to visualize and measure these changes in airflow while monitoring variables such as Mach number and altitude pressure.

Dr. Rich Roberts, chief of the store separation section of the aerodynamics branch of the Arnold Engineering Development Complex, examines a directed energy system turret positioned on a puncture in the 4ft transonic wind tunnel at Arnold Air Force Base, Tenn., March 5, 2021. The branch plans to expand DE wind tunnel testing capabilities later this year with the addition of the Integrated Directed Energy aero-optic substitute, which is a scale model of an aircraft F-15 capable of testing laser pods. (Air Force photo by Jill Pickett)

A recent DE test in the 4 foot transonic wind tunnel, or 4T, is the culmination of about eight years of work. AEDC engineers worked with MZA Associates Corp. as part of innovative small business research projects, or SBIR, and commercial readiness, to develop the Aerodynamic Insulation Measurement System, or AIMS, to enable aero-optical DE testing in wind tunnels.

“Simply put, this system transmits a laser to the model, uses some kind of miniaturized optical bench inside the model, and then uses optical fibers to route the data to a wavefront sensor system,” said Roberts. “From there, we can analyze the data that tells us how the laser was impacted by the flow field of the tunnel around the model. “

MZA was also the client of the recent test. The company worked with the Defense Advanced Research Projects Agency on a supersonic aerodynamic attenuation project with the goal of reducing the impact of high-speed flow on a turret. A prototype of a flow attenuation barrier was tested in 4T.

A directed energy system turret is positioned on a puncture in the 4-foot transonic wind tunnel at Arnold Air Force Base for testing by the Aerodynamics Testing Branch of the Arnold Engineering Development Complex, March 5 2021. Wind tunnel testing allows system developers to see the impact of airflow disturbances on the DE beam. (Air Force photo by Jill Pickett)

“We are looking at how well this design controls airflow over the turret to minimize the impact of moving air on system performance,” said Roberts. “We also compare the tunnel test data to previously generated CFDs [computational fluid dynamics] data to ensure that the simulations correctly represent the actual data. This test in 4T was the first time that this system had been tested experimentally under supersonic conditions, in addition to the first time that the AIMS system had been used at AEDC. The test went very well, getting all the priority data over two days of testing. A first review of the data shows a significant improvement in beam quality thanks to this new aerodynamic fence design.

Building on this new capability, AEDC is working as part of an SBIR project to develop the Integrated Directed Energy Aero-Optic Substitute, or IDEAS, which is a scale model of an F-15 aircraft capable of testing nacelles. laser. IDEAS hardware is expected to undergo acceptance testing later this year.

“The ability to perform aero-optical testing of directed energy systems in wind tunnels represents a new testing capability for AEDC,” said Roberts. “As more and more DE systems are developed and integrated into aircraft, we will be able to assist with design decisions, the creation of job envelopes, the definition of aircraft loadings. ‘adjacent weapons and other items commonly required by program offices and manufacturers. “

High speed wavefront measurements were made on the opening of the directed energy nacelle. The image on the left shows a shock on the opening. The image to the right shows an example of optical distortion predicted by computational fluid dynamics formed above the aperture for similar flow conditions. (image by MZA Associates Corp.)


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