Hypersonics Chief Details Journey of Building the World’s Most Speed-Defying Aircraft

2025 Durand Lecturer Delves into the History and Future Prospects of Supersonic Systems

By Anne Wainscott-Sargent, AIAA Communications Team

[Link] Kevin Bowcutt, principal senior technical fellow and chief scientist of Hypersonics at The Boeing Company, delivers remarks Monday, January 6, at the 2025 AIAA SciTech Forum in Orlando, Florida, during the AIAA Durand Lectureship for Public Service. AIAA-©

ORLANDO, Fla.- Kevin Bowcutt has spent over four decades advancing the field of hypersonic flight, notable for achieving speeds greater than five times the speed of sound, or faster than Mach 5.

As this year's recipient of the AIAA Durand Lectureship for Public Service, Bowcutt, who serves as principal senior technical fellow and chief scientist of Hypersonics at The Boeing Company, shared how far hypersonic flight capabilities have come from its origins after World War II at the 2025 AIAA SciTech Forum in Orlando.

The age of hypersonics began almost 76 years ago. In 1949, the U.S. Army took a captured German V2 rocket and added a WAC Corporal second stage to the top before launching it into the atmosphere from White Sands Proving Grounds. The experimental rocket achieved Mach 7 or 8, depending on the atmospheric temperature at the point of entry, noted Bowcutt.

Over the next 50 years, hypersonics was relegated to the domain of rocket-propelled systems, with both NASA's Apollo space capsule and later the Space Shuttle achieving hypersonic speeds, with the capsule reaching Mach 37, or almost 25,000 miles per hour, on its return from the moon.

Bowcutt interspersed personal anecdotes of his own journey in the field while highlighting the development challenges of hypersonic systems. He emerged on the scene in 1984 as a doctoral student at the University of Maryland. Under the tutelage of John Anderson Jr., a leading authority on hypersonics and the former professor emeritus in the university's Department of Aerospace Engineering, Bowcutt began his first foray into advancing the field of hypersonics. His task: to take rudimentary forms of parametric geometry generation, computational fluid dynamics, and mathematical optimization to find complex curved aircraft shapes that rode on their own shock waves and performed better than the state of the art.

"It worked. I found shapes that performed quite a bit better," he shared.

In February 1986, following the Challenger disaster, President Reagan announced the X-30 National Aero-Space Plane program. Bowcutt spent seven years on the effort, helping design a horizontal takeoff and landing aircraft that could fly all the way into orbit.

"It was exciting. The thought of doing this as a 25-year-old at the time was just thrilling," he recalled. "We discovered a lot of things. One of them was a single stage orbit is not possible. It wasn't then and it still isn't today. We learned how to design air-breathing hypersonic vehicles. What we learned about scramjet (supersonic combustion ramjet) engines in this program eventually flew on X-43A by NASA," he recalled.

Today, that same enthusiasm is evident in Bowcutt, who has been named an AIAA Fellow, a Fellow of the Royal Aeronautical Society, and a member of the National Academy of Engineering.

"I know from my 40 years of experience that hypersonic vehicle design is really fun and interesting because it's really hard and very challenging," he explained.

"One of the things we want to do is get from point A to point B in the world faster than we currently can at about Mach 0.8," he added.

Bowcutt detailed the multitude of challenges of hypersonic aircraft design, including the balancing act of navigating extreme aerodynamic heating and temperature spikes, which results in the introduction of different materials, notably high-temperature metals and ceramics. But those materials are not necessarily easy to build or affordable to buy, he noted.

The hypersonics pioneer also described both the advantages and challenges of different hypersonic systems, explaining the effects of temperature, propellant type, and size of an engine that could affect drag and other performance issues on the aircraft. Often solving one challenge created another.

"It's challenging to integrate a relatively larger engine on an airframe," said Bowcutt to illustrate one common difficulty with these systems. "These vehicles must be highly integrated to make the whole system work together - every component, every discipline, the aerodynamics, propulsion, thermal protection, the structures - are all interrelated and interact with each other. You're operating on relatively small margins."

A positive development, he noted, was the emergence of multidisciplinary design optimization, developed over the last 25 to 30 years, which he credits with helping hypersonic system designers optimize their designs through modeling tools to help solve integration challenges faster.

The idea of air-breathing hypersonic flight - where the plane gleans oxygen for combustion from the air, just as conventional jets do - began in 1958 when a NACA researcher came up with this idea, "Could we burn fuel in a supersonic air stream?"

Bowcutt said it took five decades to prove the technology. Not carrying oxygen on board for fueling the engine significantly reduced the vehicle's size and weight. In 2004, NASA flew the X-43A with Boeing support, and proved the aircraft could generate positive net thrust with a scramjet propulsion system. It set several airspeed records for jet aircraft. At the time, it was the fastest jet-powered aircraft on record at approximately Mach 9.6.

In the 2010-2013 timeframe, the Boeing X-51 Waverider, an uncrewed research scramjet experimental aircraft for hypersonic flight, was successfully flown by the Air Force with participation of DARPA, proving that air-breathing hypersonics could be practical.

"For good or bad, we now have air-breathing cruise missiles that fly at hypersonic speed," said Bowcutt, adding that the industry now seeks to achieve hypersonic reusable flight in the form of point-to-point travel and access to space using aircraft flight approaches.

During the Q&A, Bowcutt was asked if he thought passenger hypersonic aircraft was feasible.

He indicated yes, noting that Boeing in 2018 began work on designs for an aircraft that could fly people globally at hypersonic speeds.

"I had the opportunity to explore the design, looking at the future possibility. We innovated a number of things that suggested to us that it was at least technically feasible. It's another thing to look at the market and the economics," Bowcutt said.

Environmental concerns, he added, could be the biggest hurdle, one example being concerns about airport noise since supersonic aircraft engines use small fans, which result in higher jet noise.

Also, engine emissions are another issue. "When you fly at 40,000 feet, using sustainable fuels allow carbon dioxide to be recycled in the bio-environment. If you fly at 100,000 feet, CO2 doesn't cycle very quickly. Not only that, water is a greenhouse gas as well as CO2 and water and nitric oxide both destroy atmospheric ozone. So, there's some interesting challenges we still have to conquer."

A final question to Bowcutt was what has he learned from the successes and failures he has experienced in his career.

"I tend to not be risk averse. I tend to like to push the boundary," he responded. "When you're pushing the edge of the envelope, you just have to know that not everything is going to go perfect. But the thing I find thrilling is what you learn from it. That's what makes life exciting - to continue to learn, to grow, to understand the world around us, and how to manage and tackle it."

Following the talk, Dilip Srinivas Sundaram, associate professor at the Indian Institute of Technology Gandhinagar, called Bowcutt's presentation "very interesting. ...I don't think prior to this lecture I had a good understanding of the complexity of hypersonics flight. This talk gave me a sense of how difficult it is. It may take another 40 years to realize hypersonic flight."

"I think Dr. Bowcutt gave a very comprehensive story of hypersonics from where it began and even new details that a common person might not know like the U.S. taking an old missile, which started the journey of the U.S. into hypersonics," added Alex Cintron, a member of the AIAA High Speed Air Breathing Propulsion Technical Committee who is pursuing a master's in aerospace engineering from the University of Florida in Gainesville.

"One of my goals is to go into hypersonics," he added, after getting a photo with Bowcutt on stage.

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