A RESEARCH project called Quiet Spike, which investigates suppression of sonic booms, has begun at NASA’s Dryden Flight Research Center, at Edwards AFB, California. A joint team of Gulfstream Aerospace and NASA Dryden engineers and technicians has fitted a 24ft (7.3m) retractable spike on the nose of Dryden’s F-15B research test-bed aircraft. Made of composite materials, Quiet Spike weighs 4701b (213kg) and extends from 14ft (4.26m) in subsonic flight to 24ft (7.3m) in supersonic flight.
It creates three small shock waves that travel to the ground, parallel with each other. These produce less noise than the typical shock waves which build up at the front of an aircraft as it reaches Mach 1 or 760mph (l,220kmh), the speed of sound at sea level. Because of sonic boom intensity, the Federal Aviation Administration bans all supersonic flight over land, except in some military flight corridors.
Gulfstream was awarded a patent for Quiet Spike in March 2004 and it underwent extensive ground and wind tunnel testing before it was installed on the F-15B. The first evaluation flight was made on August 10 this year, and subsequent flights have evaluated the spike’s structural integrity. Future flights will test sonic boom suppression theory in a real flight environment. Once Quiet Spike has proved itself structurally sound, it can be incorporated onto advanced low-boom configuration aircraft to further control and mitigate adverse acoustic impacts of supersonic flight.