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Supersonic Baby Boom: NASA F-15B Chases the Modified Shock Wave of Altered Jet
10.08.03
 
NASA's F-15B research testbed jet flys in the supersonic shockwave of an F-5E jetPhoto left: NASA's F-15B research testbed jet from the NASA Dryden Flight Research Center flew in the supersonic shockwave of a Northrop Grumman Corp. - modified U.S. Navy F-5E jet. (NASA photo by Carla Thomas)

Most people never hear loud sonic booms because supersonic aircraft are restricted to flying in a few special corridors. While this limits the impact of sonic booms on the population, it also inhibits the growth and utilization of high-speed flight. Now Northrop-Grumman Corp. is working with NASA researchers to improve the characteristics of sonic booms in an effort to make their impact less felt. This could one day open much more of the skies to supersonic travel, removing a key obstacle to the expanded application of high-speed flight.

When Chuck Yeager blasted through the sound barrier in the skies above Edwards Air Force Base nearly 56 years ago, the world's first sonic boom thundered across the California desert for miles.

Now Northrop-Grumman has added new contours to a supersonic F-5E jet to reshape and refine the characteristics of the supersonic shock wave it produces when it flies faster than the speed of sound. A NASA F-15B research jet from the agency's Dryden Flight Research Center flew in the supersonic shockwaves of the modified U.S. Navy F-5E jet to quantify characteristics of the modified sonic booms in late August.

The flights were in support of the Shaped Sonic Boom Demonstration (SSBD) project, which is part of the Defense Advanced Research Projects Agency's Quiet Supersonic Platform (QSP) program. The overall QSP program is an ongoing effort to identify and mature technologies that could allow future military and business aircraft to operate with sonic booms that are both smaller in footprint and perceived sound levels.

During the recent demonstration, the F-15B flew two flights through the Edwards Air Force Base supersonic corridor behind the F-5E in order to measure the F-5E's sonic boom characteristics.

Flying behind and below the F-5E, and using its specially instrumented nose boom, the F-15B recorded many shockwave patterns from the F-5E at a speed of Mach 1.4.
Modified U.S. Navy F-5E Shaped Sonic Boom Demonstration aircraft

Photo right: Northrop Grumman Corporation's modified U.S. Navy F-5E Shaped Sonic Boom Demonstration aircraft. (NASA photo by Carla Thomas)

In addition to the airborne data collected by the F-15B, sonic boom data was gathered on the ground by two NASA Dryden-developed Boom Amplitude and Direction Sensors (BADS) in order to obtain ground-level sonic boom signature data. NASA's Langley Research Center funds the agency's participation in this pioneering effort, and furnishes engineers and some ground sensors used in the Mojave Desert.

The objective of the SSBD project is to show that by modifying the shape of an aircraft, the shape and behavior of supersonic shock waves can be significantly altered, thereby reducing the intensity of sonic booms. This technology could eventually enable unrestricted supersonic flight over land, possibly helping usher in a new era of supersonic aircraft.

While more research and development needs to happen before quieter supersonic aircraft are the norm, researchers are encouraged by the tests so far. Edward Haering, principal investigator for the SSBD project for NASA Dryden, is pleased to see this technology moving from the theoretical to the actual: "The ground-level sonic boom recordings we gathered with the modified and unmodified aircraft validates that the shaped sonic boom theory works with real aircraft through the real atmosphere."

NASA's F-15B also flew baseline probe flights in 2002 in support of the SSBD project, providing measurements of the unmodified F-5E to record changes produced by the modifications.

NASA Dryden has expertise in air and ground-based sonic boom measurement techniques, having accomplished several sonic boom studies over the years.

By Gray Creech, Public Affairs, NASA Dryden Flight Research Center