‘This is rocket science’

'This is rocket science'

Aerospace engineering students push boundaries of hypersonics

By Michael Miller Email MichaelEmail Michael 513-556-6757

6 minute read April 23, 2025 Share on facebook Share on Twitter Share on LinkedIn Share on Reddit Print StoryLike

At the University of Cincinnati's Hypersonics Lab, students pursue new technology for high-speed travel and exploration.

Aerospace engineering has always had a preoccupation with speed. Now researchers in UC's College of Engineering and Applied Science are pushing the boundaries of what is possible, practical, reliable and safe at five times the speed of sound or more than 3,800 mph.

"The bottom line for aerospace is to go farther, faster with more payload. That's the fundamental question for anything that flies," said Prashant Khare, director of UC's Hypersonics Lab. "And we strive every day to come up with new technologies or science concepts that might lead to improvements."

Hypersonics is getting increasing attention for military applications in the race to develop faster weapons - and perhaps one day aircraft - capable of evading deterrent technology.

"From a physics point of view, the limitation is the speed of light," said Khare, head of UC's Department of Aerospace Engineering and Engineering Mechanics.

"But it's an interesting question," he said. "The challenge is not only how fast we can go, but do we have materials that will withstand the speeds we want to go?"

UC Professor Prashant Khare, pictured at UC's data center, conducts simulations on new technology related to hypersonic flight. Photo/Andrew Higley/UC Marketing + Brand

The crew of Apollo 10 holds the speed record for human flight, reaching more than 24,000 miles per hour on their return trip from the moon. At such extreme speeds, the friction with the atmosphere generates intense heat. Space modules must withstand temperatures of more than 2,700 degrees Fahrenheit.

Researchers are finding new ways to withstand this inferno, he said.

"Friction creates the heat. Can we come up with new materials or cooling technologies so we can go fast?" Khare asked. "The next question is how do we go that fast? That is more related to traditional propulsion or combustion sciences."

These questions are fundamental to aerospace engineering and still generate a lot of interest among engineering students, Khare said.

"Students are very excited about hypersonic research," he said. "I've taught a class called gas dynamics for many years that introduces students to these concepts. I've gotten comments from students about how excited they are to learn more about it."

A lot of it is counterintuitive or even mind-bending to think about.

Prashant Khare, UC Professor of Aerospace Engineering

UC engineering student Jeremy Redding said aerospace engineers push the envelope of what is possible and safe, starting with the first rockets in the 1940s, leading to the first human missions to space in the 1950s and '60s.

"Atmospheric reentry was the next real-world application of theories of hypersonic flight," Redding said. "A controlled flight or 'falling with style,' to quote 'Toy Story,' was a consequence of circumstances that we had to get back down."

The Hypersonics Lab's work at Digital Futures has examined how changing surface dynamics alters the fundamental physics of hypersonic flight systems. Engineers also are learning more about the bizarre physics observed at high speeds, Khare said. Fluids behave weirdly at hypersonic speeds as molecules break apart and reform, creating a nonequilibrium state.

"A lot of it is counterintuitive or even mind-bending to think about," he said.

An experimental hypersonic aircraft accelerates to Mach 10 after its booster launch in 2004. Photo/AFRC

And their collaboration with the Army Research Laboratory is leading to engine improvements to prevent stalling at such high speeds, Redding said.

"This is just the beginning," Redding said. "Hypersonics is a multidisciplinary field of research that requires the insight of a passionate community intentionally pursuing the knowledge it has to go faster and higher."

At least for now, hypersonic flight is impractical for commercial aviation because of the massive gravitational or g-forces passengers would have to withstand. But it's of immense interest in military and cargo applications, Khare said.

Hypersonic weapons such as Germany's V-2 rocket were deployed as early as World War II. More recently, Russia used hypersonic missiles in its attacks on Ukraine. Russian President Vladimir Putin threatened to use them against NATO allies that provided missiles for Ukraine.

"And China tested one of its own. So there's been a lot of investment in improving hypersonic technologies," he said.

In his lab, Khare and his students use computer simulations to study the fundamentals of new propulsion systems for rotating detonation engines, which are more efficient than today's jet engines, and supersonic combustion ramjet engines such as those depicted in the opening scene of the 2022 blockbuster movie "Top Gun: Maverick."

"We're trying to create an air-breathing 'rocket' that doesn't have to carry oxidizer," he said. "This can make a rocket more efficient so you can carry more payload."

Engineers are deploying tools such as spectroscopy, Raman scattering and photonic Doppler velocimetry to study hypersonics. Meanwhile, supercomputers allow Khare and his students to record hypersonic variables in fine detail in simulations. Capturing just one millisecond of hypersonic flight in simulation can require millions of computing hours.

"With advances in experimental diagnostics, technology and computing, we are now at a point where we can understand it because we have these new tools," Khare said.

But there is still much to explore. And with so much external interest in this topic from government agencies and aerospace companies, careers in hypersonic technology are promising, he said.

"When people talk about something simple they'll often say, 'It's not rocket science,'" Khare said. "But this is. This is rocket science."

Featured image at top: An illustration of the Orion spacecraft demonstrates the intense heat the capsule must withstand as it re-enters Earth's atmosphere at 25,000 miles per hour. Illustration/JSC

In his Hypersonics Lab, UC Professor Prashant Khare and his students are pushing the boundary of technology in hypersonic flight. Photo/Andrew Higley/UC Marketing + Brand

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