Plasma flows into a chamber made from stainless steel several inches thick.

Graduate student Alex Thompson, left, and Hisham Ali, right, discuss settings for their plasma tunnel.

One-of-a-kind plasma tunnel recreates extreme conditions spacecraft face upon reentry

When a spacecraft returns to Earth, it slams into the atmosphere at roughly 17,000 miles per hour. The resulting shockwave tears apart air molecules, creating a superheated plasma that can reach temperatures many times hotter than the surface of the sun. 

Those extreme conditions pose one of the greatest risks in spaceflight, said Hisham Ali, assistant professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences. 

The dangers became tragically clear during the Columbia disaster in 2003, when plasma entered the space shuttle through a damaged heat shield during reentry. The shuttle disintegrated, killing all seven crewmembers, including CU Boulder alumna Kalpana Chawla. 

Ali has dedicated his career to helping prevent similar accidents. 

Safer space reentry

“One of the most critical and dangerous phases of any space mission is when spacecraft reenter Earth’s atmosphere,” Ali said. “If we’re taking more humans to orbit through space tourism, we need to do that safely and effectively, and that’s a challenging problem.” 

To tackle that challenge, Ali and his team opened a new research facility on CU Boulder’s East Campus in late 2025. Known as an inductively coupled plasma tunnel, the facility generates streams of plasma that flow at hundreds to thousands of miles per hour and reach temperatures of 9,000 degrees Fahrenheit and higher. 

The one-of-a-kind facility allows researchers to study how materials and technologies behave under hypersonic conditions—flight at Mach 5 and faster. The team is also exploring whether powerful magnets could someday help maneuver vehicles traveling at those extreme speeds. 

“There’s not a chamber exactly like this anywhere in the world,” Ali said. 

A lab that glows 

Inside a windowless laboratory, a 40-kilowatt generator powers the plasma tunnel. The system includes a quartz-glass nozzle that feeds into a larger stainless-steel chamber. 

“I think we’re ready to light,” Ali said to his team. 

Moments later, a lavender-colored plasma ignites inside the glass tube before rushing into the chamber, where surfaces glow orange from intense heat. 

To recreate hypersonic conditions, the researchers need both speed and heat. They first inject argon gas into the tunnel, while a powerful vacuum system pulls the gas through the chamber. The vacuum can move more than 20,000 cubic meters of air per hour, making it one of the most powerful university systems of its kind in the U.S. 

The team then applies strong radio waves that generate electric currents in the gas, transforming it into plasma. Once the argon plasma is established, researchers can inject Earth’s atmosphere—or the atmospheres of other planets. 

Keeping things cool 

Ali’s fascination with hypersonic flight began during a childhood visit to Space Camp at the U.S. Space and Rocket Center in Huntsville, Alabama. There, he saw a demonstration of a heat-shield tile similar to those used on NASA’s space shuttles. 

Now, the plasma tunnel allows Ali and his students to expose materials, sensors and other technologies to conditions similar to those experienced during atmospheric reentry. The researchers have already partnered with one aerospace company to test a new heat-resistant material and plan to work with several more partners. 

The facility can also simulate environments beyond Earth. 

“Once our plasma is lit, we can inject carbon dioxide and create a plasma made of flowing carbon dioxide, similar to what a spacecraft might experience at Mars,” Ali said. 

Beyond testing materials, the team is investigating whether magnetic fields can help control hypersonic vehicles. Because plasma consists of charged particles, powerful magnets may be able to alter the flow of plasma surrounding a spacecraft and generate forces that could help steer it during flight.