UNIVERSITY PARK, Pa. — Supersonic jet aircraft may once again fly over land and sea as sonic booms become sonic thumps, according to a NASA project with Penn State collaboration that will take place in the skies over Galveston, Texas.
Supersonic aircraft fly faster than the speed of sound and when they do, they create a high-energy sound wave that travels behind them and is heard by anyone who intersects that wave. Luckily, because the aircraft are moving, the wave moves, and any particular location only hears the sonic boom for a very short time. The U.S. banned civil supersonic transportation over land in the early 1970s.
The Quiet Supersonic Flight series 2018 (QSF18) will use a NASA F/A-18 research aircraft to perform a unique supersonic dive maneuver that produces a sound similar to a soft thump rather than the sonic boom heard from conventional supersonic aircraft. The flights will occur over Galveston, Texas, and help NASA better understand public response to quiet supersonic flight.
"The sonic thumps should sound like distant thunder," said Kathleen Hodgdon, assistant research professor, Penn State's Applied Research Laboratory. "We're even concerned residents will mistake them for car door slams in a typical urban environment due to background noise."
The goal is to test, in as real an environment as possible, the methods and technologies intended for future community-response testing when NASA's X-59 Quiet Supersonic Technology aircraft flies in the early 2020s. The goal is to collect noise measurements as well as human response data.
"The business jet would probably be the first on the market and that would help introduce some of the technologies that eventually would be used on the supersonic airliner," said Peter Coen, project manager of NASA's Commercial Supersonic Technology Project. "Our job is to support the science and technology behind those choices eventually making supersonic flight available to the traveling public."
At NASA, the technical monitor for the project is Jonathan Rathsam, Applied Physical Sciences, leads the contractor team. Robert Hunte from APS and Hodgdon are co-principal investigators. The team also includes researchers from the Penn State Survey Research Center, Volpe National Transportation System Center, KBRwyle, Gulfstream Aerospace Corporation, Eagle Aeronautics and Gaugler Associates.
Hodgdon's work since 2005 in supersonic noise measurement and human response tests contributed to the design of this current effort. In fact, she taught one of the first courses in sound quality, teaching students to relate noise metrics to human perception. Alexandra Loubeau, a NASA technical lead overseeing sonic boom research, took that course on the way to her doctorate in acoustics at Penn State. Rathsam, who completed his doctorate at the University of Nebraska-Lincoln, has also taken courses in the graduate program for acoustics distance learning in the College of Engineering at Penn State. The QSF18 team includes Will Doebler, Matt Collmar, Matt Nickerson and Kris Lynch, who are all Penn State acoustics graduates participating on the modeling and noise measurement aspects of the research.
Because this project includes surveying people, the University's Institutional Review Board and Survey Research Center are also involved in the project.
The team chose Galveston because the population is relatively unaccustomed to the sounds of supersonic flight. This allows the team to examine their methodology and their equipment performance before testing over much larger populations.
"We've worked towards this test for over a decade," said Hodgdon. "The team has brought together experts from across the country and I'm proud that Penn State has been able to contribute so much to the success of this research."
Hodgdon is teaming with Diana Crom, director of operations and Brian Sonak, project manager at the SRC, to gather the survey responses from the community to rate the sounds. She has a long history of figuring out how to measure human response to noise and correlate that with objective measurements of sound. Crom has worked on sonic booms since 2005.
While QSF18 will provide insight into acceptance levels for supersonic flight noise, the goal of the program is to validate testing methods with the hope of overcoming barriers to supersonic flight.