UT Researchers Receive $17.8M Grant To Create New Wind Tunnel for Materials Testing

Researchers at the University of Tennessee, Knoxville, will use a $17.8 million grant from the U.S. Air Force to create a wind tunnel that can subject samples of materials like high-temperature ceramics to hypersonic conditions—conditions experienced above Mach 5, which is five times the speed of sound.

The new wind tunnel, which will be housed at the UT Space Institute in Tullahoma, Tennessee, part of UT's Tickle College of Engineering, will join only a handful of wind tunnels in the world that can mimic the conditions of hypersonic flight. The work is crucial to the future of hypersonic vehicles such as space shuttles, which slam into Earth's atmosphere at nearly Mach 25. That tremendous speed heats the shuttle's surface above 2600 degrees Fahrenheit and subjects it to extreme pressures for up to 15 minutes.

The most vulnerable parts of these vehicles, such as the nose and leading edges of wings, are covered in specialized heat-resistant materials called the thermal protection system.

"The TPS is not continuous. Every joint between tiles, and even the glue that sticks the TPS to the fuselage, is a weakness," said materials scientist Jacqueline Johnson, a professor in the Department of Mechanical, Aerospace, and Biomedical Engineering at UTSI. "We have had two glaring examples of what happens when the TPS is weak or damaged in the Challenger and Columbia space shuttle disasters."

Creating access and opportunities

Once completed, the new wind tunnel will also help alleviate the yearslong waiting list for these advanced facilities. "We have all these different kinds of wind tunnels that each specialize in examining some aspect of hypersonic flight—aerodynamics, gas chemistry, material degradation during flight—but nobody has the capability to replicate full hypersonic flight conditions," said MABE Assistant Professor Mark Gragston. "There's a big market for increased testing capability in academic research because that's where new materials are being developed."

The project helps establish expertise and capabilities in fabrication, testing and evaluation of new materials for use in extreme engineering environments and, equally important, helps to establish a workforce trained to tackle this challenge, Gragston said.

"We know this skillset and knowledge are desired by industry partners working in hypersonic system development," he said. "Developing a capable workforce is a crucial step in improving the scale economy for these materials and is in line with current initiatives led by the government and industry."

A team approach

The $17.8 million grant, which is being funded by the U.S. Air Force through the Air Force Research Laboratory in Ohio, is being headed by Johnson and MABE Assistant Professor Damiano Baccarella, an expert in hypersonic aerothermodynamics who has previously overseen construction of a hypersonic wind tunnel. They are joined by four other investigators from UT and the University of Dayton Research Institute, creating a team with expertise in hypersonic flow modeling, materials development, experimental flow diagnostics and wind tunnel testing.

"This team was carefully chosen to bring different aspects together, and nobody is trying to be the boss," Johnson said. "There's a lot of work to do, and it cannot be done by UTSI alone."

Over the next four years, the world-class team will oversee the construction of an unparalleled hypersonic wind tunnel facility and a multitiered workflow that should accelerate the discovery of new TPS materials.

For example, new TPS candidate materials currently must go straight from laboratory-scale tests to large-scale wind tunnel evaluations. The UTSI tunnel will change that.

"If a subpar material fails in a large-scale test, that's a huge waste of money and time," said Gragston. "We're building an intermediate-scale capability that will tell us whether a new material is worthy of those more expensive tests in a quicker time span and with less expense."

The team is also working to validate and improve simulations of TPS materials, which will further close the gap between ground-based tests and flight conditions. Those simulations will benefit from unique testing capabilities at UTSI, like noninvasive laser-based analysis of the chemical reactions around materials during testing.

Such diagnostic capabilities are available at UT because that is where they were developed—some by Gragston and another member of the team, MABE Professor Zhili Zhang.

"We have more advanced measurement capabilities at UT than what is usually available in the facilities at Arnold Engineering Development Complex at Arnold Air Force Base or at the National Aeronautics and Space Administration," Gragston said. "We're going to be applying many of them to this hypersonic testing environment for the first time."

The grant also funds graduate students to work under each of the participating investigators. The students will advance TPS material research and gain an incomparable understanding of the infrastructure behind a hypersonics facility.

"There are several types of hypersonics facilities, and you can learn how to build all of them from textbooks except for this kind," Gragston said. "The students who are around while this is being built, and are helping build it, will have a truly unique opportunity."
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MEDIA CONTACT:

Jennifer Johnson (865-974-4448, jenniferjohnson@utk.edu)

Provided by University of Tennessee at Knoxville