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Volume 46 | Issue 2 | March 2004


photo: Northrops modified U.S. Navy F-5E.

Dryden continues to work with partner Northrop Grumman Corp. to study sonic booms using Northrop's modified U.S. Navy F-5E Shaped Sonic Boom Demonstration aircraft, pictured here.
NASA Photo / Tom Tschida

NASA, Northrop study sonic boom reduction

By Gray Creech
Dryden Public Affairs

NASA and Northrop Grumman Corp. are continuing the quest to reduce the intensity of sonic booms by collecting the largest set of sonic boom data recorded in 20 years.

This effort is identifying and maturing technologies that could eventually enable unrestricted supersonic flight over land by future military and business aircraft, possibly ushering in a new era of supersonic flight.

"This represents the beginning of a new age in air transport, and we intend to capitalize on this breakthrough," said Richard Wlezien, manager of NASA's Vehicle Systems program.

Last year, during the successful Shaped Sonic Boom Demonstration (SSBD) project, a government and industry team proved the theory that by carefully altering the contours of a supersonic aircraft, both the shock wave produced by the aircraft in flight and the wave's accompanying sonic boom can be shaped to reduce noise volume. The team included Langley Research Center, Hampton, Va., Dryden, the Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., and Northrop Grumman's Integrated Systems sector, El Segundo, Calif.

"Northrop Grumman is proud to be able to contribute significantly to research that could revolutionize military and civil aircraft," said Charles Boccadoro, manager of Long Range Strike Systems for Northrop Grumman.   "We will use the knowledge gained in these demonstrations to further our understanding of efficient supersonic flight."

Using the same specially modified F-5E aircraft used in the earlier research flights, the renamed Shaped Sonic Boom Experiment team completed a second round of experiments, flying 21 supersonic flights at Mach numbers ranging from 1.35 to 1.4 and altitudes from 32,000 to 34,000 ft.

"It was very satisfying to be part of the team that collected this extensive set of data," said Peter Coen, supersonic vehicle sector manager for the NASA Vehicle Systems program. "We now have the kind of information researchers need to really understand the details of sonic boom shaping in realistic flight conditions."

Several of the flights utilized Dryden's F-15B research testbed aircraft flying in close formation with the F-5E to measure the details of the shock wave signature. During the flights, 45 shock wave patterns were measured by the F-15B at various distances and orientations from the F-5E.

On other flights, an unmodified F-5E flew a few seconds behind the demonstration aircraft to provide a baseline sonic boom measurement to validate the reduced boom produced by the demonstrator.

A U.S. Air Force Test Pilot School Blanik L-23 sailplane carrying a microphone on the left wingtip, and a pressure transducer on the side of the fuselage, flew silently under the flight path of the F-5E at an altitude of 10,000 feet in order to record sonic booms above the influence of most atmospheric turbulence.

In addition to the airborne data collected by the F-15B and the sailplane, sonic boom data was gathered on the ground by an array of 42 sensors and recording devices stretched out over two and a half miles under the flight path of the F-5E. Dryden-developed boom amplitude and direction sensors, along with microphone recorders provided by Langley, Wyle Labs and Gulfstream Aerospace, recorded ground-level sonic boom signature data.

"We now have over 1,300 high-quality recordings of sonic booms," said Ed Haering, Dryden's principal investigator for sonic boom research. "In all these flights the SSBD aircraft had shaped (modified) sonic booms, with interesting differences in the shapes with variations of Mach number and altitude."

Funding for the second round of flights was provided through NASA's Vehicle Systems program. Northrop Grumman's Integrated Systems sector engineers modified the U.S. Navy F-5E aircraft into the SSBD aircraft as part of the first round of flights, sponsored through DARPA's Quiet Supersonic Platform (QSP) program.