Gulfstream's Sonic Silent Treatment

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It's all about the spike. Equipped with a Gulfstream-patented prosthetic nose (a.k.a. "Quiet Spike" sonic boom mitigator), a NASA F-15 managed to convert its transonic sound signature from a climactic boom to a series of small "almost inaudible" rumbles. The test flight program concluded this month, marking a critical step "moving us forward in the development of a supersonic aircraft," Pres Henne, Gulfstream's senior vice president for the project, last week told the Savannah Morning News at Savannah/Hilton Head International Airport. Aerodynamically, size matters -- the telescoping spike rests at a length of 14 feet in subsonic flight. It extends to its full length of 24 feet as that speed once called the sound barrier is penetrated. The result is an overall increase in length for the aircraft that softens shock waves spreading outward from the plane. If you're thinking that would make a nice selling point for a supersonic business jet, Gulfstream agrees.

For Gulfstream, development of the spike addresses practical overland supersonic operations that hinge not only on economics, but also on environmental factors. "From the outset it has been understood that the sonic boom must be reduced to acceptable levels before consideration could be given to developing a prototype quiet supersonic jet," Henne told the newspaper. According to Henne, fitting the Quiet Spike to a supersonic business jet specifically constructed to muffle the adverse sounds of supersonic flight is on the agenda. NASA and Gulfstream have been testing the structural integrity of the spike since June. So far, performance comes with a price -- the spike weighs about 470 pounds.