NASA - National Aeronautics and Space Administration

NASA Dryden coop student Sarah Arnac makes last minute preparations of a sonic boom-measuring microphone during boom measurement flights on Sept. 9, 2009. (NASA Photo / Tom Tschida) Members of the United Nations-affiliated International Civil Aviation Organization, or ICAO, monitored a series of sonic boom research flights conducted by NASA's Dryden Flight Research Center on Edwards Air Force Base, Calif., Sept. 9. The effort was coordinated by the NASA Aeronautics Research Mission Directorate's Supersonics Project office at NASA Headquarters.

Members of ICAO's Committee on Aviation Environmental Protection, including the Aircraft Noise Working Group and Supersonic Task Group, witnessed the flight demonstrations. Headquartered in Montreal, the ICAO is involved with regulation of civil supersonic flight over land.

"The visit was immensely successful,” said Peter Coen, NASA's Supersonics Project manager in the ARMD. “The group was very pleased and impressed by the quality of the demonstration and the hospitality of NASA."

"From the perspective of sonic boom research and the prospect of potentially establishing a noise-based rule for supersonic overland flight, the visit was a major milestone," Coen continued.

"The Supersonic Task Group is tasked with monitoring the progress on supersonic aircraft development,” Coen added. “For most of them, particularly the international members, this was their first-ever experience with low sonic booms in a realistic setting. The experience gave them a new perspective on what the noise level numbers really mean, and allowed them to appreciate the fact that it might be possible to reduce the boom to acceptably low levels."

Dummies aren't deaf, as attested by these sonic boom-measuring mannequins with sensitive microphones inside the ears designed to mimic the acoustic reception of a person. (NASA Photo / Tom Tschida) NASA’s Supersonics Project has been working closely with the Federal Aviation Administration’s Office of Environment and the FAA representatives on the ICAO’s Supersonic Task Group to help it develop a research roadmap called the Community Response to Sonic Booms. Currently in draft form, the roadmap document is intended to provide guidance on the research required to support the development of noise standards for sonic booms.

Once adopted, this roadmap can be used by ICAO member organizations to advocate for resources to conduct sonic boom research. NASA's Supersonics Project will align its research activities with the elements of this roadmap. This research will include more low boom exposure testing like the recent Sonic Booms on Big Structures work that continues testing the effects of booms on buildings and the attendant indoor noise.

During the recent sonic boom research flights, two NASA Dryden F/A-18s flew both straight supersonic flight profiles as well as a unique supersonic diving profile designed to present a quieter sonic boom to specific locations along their flight path. The F/A-18s flew in Edwards' High Altitude Supersonic Corridor at 32,000 to 49,000 feet altitude for the supersonic runs.

This research complements previous efforts to measure the pressure and loudness of sonic booms on both older- and newer-construction housing on the base. The earlier base housing research showed that indoor noise from sonic booms might be more annoying than the same booms heard outdoors.

NASA supersonics project personnel brief ICAO team members at an instrumented Edwards AFB house prior to sonic boom measurement flights on Sept. 9, 2009. (NASA Photo / Tom Tschida) Currently, Federal Aviation Administration regulations prohibit supersonic flight over land in the U.S., except in special restricted military flight corridors. Overland supersonic flight is also currently prohibited in many countries, thus the involvement of the ICAO.

A resurgent interest by the aerospace community in aircraft that can fly at supersonic speeds over land has led to several research projects to shape and modify supersonic shockwaves to reduce their perceived intensity.

Among them, the Shaped Sonic Boom Demonstrator Project by NASA, Northrop Grumman and DARPA and the QuietSpike Project by NASA and Gulfstream both demonstrated the successful suppression of sonic boom intensity on the ground.

NASA's Langley Research Center, Hampton, Va., and Gulfstream Aerospace Corporation, Savannah, Ga., are partners with NASA Dryden and the Air Force Flight Test Center in the project. The effort is funded and managed by the NASA Aeronautics Research Mission Directorate’s Supersonics Project, which supports NASA's Fundamental Aeronautics program strategy of developing systems-level, multidiscipline capabilities for supersonic civilian and military applications.

Gray Creech, Tybrin Corp.
NASA Dryden Flight Research Center