Early fighter pilots were sometimes called knights of the air, a reflection of medieval times when knights used blunted lances in jousting tournaments to dismount competitors from their horses.
Now, jet-borne jousting is combating supersonic shockwaves, hopefully enough to lessen the resulting sonic boom heard on the ground.
Gulfstream Aerospace and NASA’s Dryden Flight Research Center have teamed in a project called Quiet SpikeTM to investigate the suppression of sonic booms.
The project centers around a retractable, 24-foot-long lance-like spike mounted on the nose of NASA Dryden’s F-15B research testbed aircraft. The spike, made primarily of composite materials, creates three small shock waves that travel parallel to each other all the way to the ground, producing less noise than typical shock waves that build up at the front of supersonic jets.
After mounting the giant spike on the aircraft, NASA Dryden engineers and technicians, working alongside their Gulfstream counterparts, conducted various ground-based structural tests of the telescoping spike before taking it to flight.
“The partnership between Gulfstream and Dryden during Quiet Spike installation and ground testing on the F-15B has produced a wealth of valuable information,” said Leslie Molzahn, NASA Dryden’s operations engineer on the project. “The duration of this flight test effort will prove to be exciting and informative for everyone involved.”
“Working with Gulfstream has provided a significant advantage to this flight research project,” added NASA project manager Michael Toberman. “This project merges Gulfstream’s manufacturing expertise with NASA Dryden’s flight test expertise.”
Since flights began on Aug. 10, the system’s structural integrity has been put to the test before moving on to sonic boom suppression measurements. While these tests won’t actually ‘quiet’ the F-15’s sonic boom, they will show that the spike’s design is capable of use in a real flight environment. The flights and data being recorded are closely monitored in NASA Dryden’s mission control.
Shockwaves develop around aircraft as they near Mach 1, or the speed of sound, about 760 mph at sea level. When an aircraft travels supersonically, the resulting shockwaves can produce a loud sonic boom that rattles windows and nerves on the ground under a supersonic jet’s path.
As a result, the Federal Aviation Administration prohibits supersonic flight over land, except in special restricted military flight corridors.
Gulfstream’s Quiet Spike puts spike-induced sonic boom suppression theory to the test in the actual flight environment afforded by NASA’s supersonic F-15B. The aircraft has served NASA and industry for years as a flying wind tunnel and supersonic testbed.
Once the Quiet Spike has proven to be structurally sound, it can be incorporated with confidence onto advanced low-boom configuration aircraft to further lessen the impact of sonic booms.
“By changing length in-flight, Quiet Spike will demonstrate yet another way to shape the sonic boom,” said Gulfstream spokesman Robert Baugniet. “It’s a necessary step toward low boom aircraft design and truly quieting the sonic boom.”
In 2003 and 2004, NASA Dryden worked with DARPA and Northrop Grumman on the Shaped Sonic Boom Demonstration project, which flew a highly modified F-5 aircraft to prove that aircraft shaping can reduce sonic boom intensity.
PHOTO EDITORS: High-resolution photos to support this release are available electronically on the NASA Dryden web site at: http://www.dfrc.nasa.gov/Gallery/Photo/Quiet_Spike/index.html.
For more information about NASA Dryden Flight Research Center and its research projects, visit: https://www.nasa.gov/centers/dryden on the Internet.
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