Gulfstream, & NASA, studying Supersonic Shockwaves.

Gulfstream, NASA Dryden Joust with Supersonic Shockwaves.

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 Spike 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.