Introducing the Plasmatron X

The sky isn’t the limit for a unique experimental facility that will help humanity reach Titan and beyond.

Written by Jenny Applequist

In hypersonic flight, an aircraft or spacecraft moves at least five times faster than the speed of sound—and thereby produces extreme heat that can push the craft beyond its physical limits. The difficulty and importance of protecting vehicles against those conditions were tragically illustrated in 2003, when slight damage to heat-shielding tiles caused the Space Shuttle Columbia to disintegrate while re-entering Earth’s atmosphere.

Now, a unique experimental facility has opened that will help ensure that such a tragedy is never repeated—and also enable unprecedented new adventures in space exploration.

“That’s our goal: that students go out there and have this unique capability to be able to take the science further than we can imagine or dream about.”

Prof. Greg Elliott, Aerospace Engineering

The Plasmatron X, which is the largest inductively coupled plasma wind tunnel in the U.S., went live on March 8 in the Center for Hypersonics & Entry Systems Studies (CHESS) in The Grainger College of Engineering at UIUC. Its purpose is to test materials to find out whether they are survivable for extreme hypersonic flight and re-entry, and to develop profiles of the conditions that would be found throughout a mission or during re-entry.

A plasma wind tunnel is a facility in which energy is added to a gas to the point that it ionizes and becomes a plasma, mimicking the atmospheric conditions encountered in hypersonic flight. In an “inductively coupled” plasma wind tunnel, there is no contact between the high-temperature plasma and electrodes.

Francesco Panerai, an assistant professor in Aerospace Engineering who is one of the leaders of the Plasmatron X effort, explains that the “pure flow” created by that contactless plasma generation is a big part of what makes the Plasmatron X a superior research tool. The absence of contact prevents contamination, creating “a pristine environment that is really the same one that vehicles find when they travel high up in the atmosphere,” he says. The result is that you can gain a much better understanding of materials’ behavior, enabling “materials-science-grade type of testing.”

Greg Elliott, an Aerospace Engineering professor who also has a leading role with the Plasmatron X, notes that its size is another important feature—and not only because larger samples and systems can be studied. “It can also produce more heat—enthalpy—over a larger area,” he says, and “we can run longer times, continuously, for hours. So we can really provide an extreme environment for long test times and then also change parameters during that time to mimic different flight and re-entry conditions.”

How extreme is the Plasmatron X? The interior can reach temperatures of about 10,000 degrees Kelvin, compared to which the surface of the Sun, at a mere 5,778°K, seems almost chilly. A serious cooling system, combined with the lack of contact between the plasma and interior walls, makes it possible to work safely with such high temperatures.

CHESS’s director, Marco Panesi, notes that “the mission of CHESS is to address all the challenges of hypersonic flight.” The Plasmatron X will be key to that mission because thermal protection is “one of the weakest links” in hypersonic systems. “But we also do a lot of modeling and simulation for the flow and the plasma around the vehicle, and radiation, and sensing,” he says.

In its first weeks, the Plasmatron X is still being tested to ensure that everything works perfectly, but researchers are already lining up to use it. For example, NASA will work with it on its Dragonfly mission, which is sending a drone to search for life on Saturn’s largest moon, Titan. Titan’s atmosphere—about 95% nitrogen and 5% methane—is very different from Earth’s. But that’s no problem for the Plasmatron X, which, Elliott notes, can simulate conditions for “any other atmospheres of planets or moons that you would want to have a re-entry system survive in.”

Elliott adds that one reason for establishing unique facilities is that UIUC graduates can be launched into the world with a background that no one else can compete with. “That’s our goal: that students go out there and have this unique capability to be able to take the science further than we can imagine or dream about.”

Researchers outside UIUC who are interested in using the Plasmatron X should contact CHESS.