By Anna Boggs
Imagine being able to fly from New York to California in less time than it takes you to go to the grocery store. While it may seem like a dream, hypersonic flight could make it a reality. To make this dream come true, new lightweight structures that are strong enough to withstand multiple flights at speeds greater than five times the speed of sound are needed. Dr. Jack McNamara is trying to make this possible by improving the understanding about how airplane structures and the air they move through interact at high speeds.
McNamara is a Professor of Mechanical and Aerospace Engineering at Ohio State University. On Nov. 13, 2018, he presented on the current technologies concerning hypersonic flight in the Mechanics Seminar Series at the University of Wisconsin-Madison.
McNamara highlighted four main constraints in hypersonic flight. First, all the dynamic systems (such as thermal, fluid, or structural) are coupled. This means they all interact and affect how each other behave. Coupling makes it impossible to analyze the systems one at a time. Next, the interactions between systems take place over very different space and time scales. Not only do you need to know the interaction between air molecules multiple times per second, you also need to know how the left wing affects the right wing after an hour of flight. Thirdly, many of the system interactions are path-dependent. It is not enough to know that the airplane flew from Seattle to Chicago, we need to know exactly what happened to it at every step along the way. All these factors not only make brute force analysis extremely computationally expensive, but they also requite unrealistically large data sets which make it impossible to track the exact time history of what happened to the aircraft.
Despite these challenges, Professor McNamara is optimistic about the future of hypersonic flight. He presented on emerging technologies that may be able to tackle these complex problems. More sophisticated material damage models would allow engineers to better understand how the material evolves and changes with use. Advanced numerical techniques could allow for better data recording over long periods of time. This would help to alleviate problems associated with not knowing the entire time history of every part of the aircraft. He hopes to eventually be able to create a “digital twin” or a computer model that has undergone the same damage as the physical aircraft to track changes in performance and safety. Finally, more experiments run at hypersonic speeds would allow engineers to verify and improve the accuracy of their models. Together these technologies may one day make sustainable hypersonic flight a reality.