Today, it takes 15 hours to fly from Sydney to Los Angeles. But what if that time could be shortened? What if crossing half the planet only takes one hour? How would we view the world? That’s the premise behind Dr. Nicholaus Parziale’s latest research on hypersonic flight.
Parziale’s focus on hypersonic flight began during his childhood, where he had a passion for mechanical and electrical things and worked on cars with his dad. Parziale got involved in hands-on lab work when he worked with Tim Singler in a lab at Binghamton University. During his graduate classes at the California Institute of Technology, he researched experimental fluid mechanics and worked with Joe Shepherd and Hans Hornung.
While such flights seem impossible by today’s standards, military planes prove that they are closer to reality than they seem. To fly between Los Angeles and Sydney in an hour, these planes would have to travel at Mach 10 or 10 times the speed of sound. Military planes can travel at Mach 2 and Mach 3, or around two and three times the speed of sound. However, what’s standing in the way is the heat and turbulence generated by these flights.
Because of how the air around aircraft behaves differently at low and high speeds, aerospace engineers must first understand how airflow works at higher Mach speeds. Incompressible flow happens at lower speeds, and the air density remains constant. But at higher speeds, compressible flow occurs, and the air compresses. However, Morkovin’s hypothesis, formulated by Mark Morkovin, claimed that airflow behaves similarly at both low and high speeds. If it were true, hypersonic planes wouldn’t need an entirely different design approach. However, there isn’t enough experimental data to decisively prove the theory.
Providing that data to prove Morkovin’s hypothesis was the subject of Parziale’s new study. Titled Hypersonic Turbulent Quantities in Support of Morkovin’s Hypothesis, it was published in Nature Communications on November 12. The authors include Parziale and six PhD students: Ben Segall, Tim Keenoy, Jaden Kokinakos, Jett Langhorn, Ahsan Hameed, and David Shekhtman. Parziale noted that he’s lucky to have great PhD students and is thankful to them for all their hard work.
Within the study, they performed careful measurements of hypersonic turbulence. The team used lasers to ionize the gas krypton without distributing the gas. That made the krypton atoms form a straight, glowing line. After waiting, they would observe how the line evolved. From the movement, you could learn more about turbulence and how much the flow is oscillating. Parziale observed how it was similar to if you dropped a leaf into the swirling flow beneath a bridge, the leaf would translate and spin. From these experiments, it was discovered that at Mach 6’s turbulence behavior is similar to that incompressible flow, which occurs at low speeds.
While Morkovin’s hypothesis isn’t entirely confirmed, the study suggests that hypersonic planes don’t need a different design. It would simplify the process and make computational demands more doable. Parziale’s next objective is to continue to expand the parameter space to test Morkovin’s hypothesis, which means higher Mach and Reynolds numbers. “If we can build planes that fly at hypersonic speed, we can also fly them into space, rather than launching rockets, which would make transportation to and from low Earth orbit easier,” Parziale says. “It will be a game-changer for transportation not only on Earth, but also in low orbit.”
