Gulfstream sees bright future for supersonic flight, but no time soon

  • 30-Jun-2008 06:27 EDT

When extended to its full 24 ft length, the 470-lb Quiet Spike produces a sine-wave sound shape that generates ground noise quieter than the Concorde’s by a factor of 10,000, according NASA’s Dryden Flight Research Center, which worked with Gulfstream on the Quiet Spike.

With the need for speed greater than ever, Gulfstream continues to pursue supersonic flight despite the U.S. government’s current prohibition on it.

“When we talk about the market in the business aircraft context, it’s all about saving time,” said Preston Henne, the company’s Senior Vice President of Programs, Engineering, and Test. He spoke about Gulfstream innovations during the AeroTech William Littlewood Memorial Lecture at the SAE AeroTech Congress and Exhibition held recently in Los Angeles.

 Henne acknowledged that supersonic flight is at least 10 years away. To make it a reality, two things must happen, he said: The government must relax its rules on sonic boom, and Gulfstream and/or another company must demonstrate a technology that passes muster with “a rational” sonic boom regulation.

Gulfstream is busy on its part, Henne said. “We’ve had a technology program in place for several years looking at ingredients to a design that can be made quiet enough to fly supersonic over land—a  lot of simulation on sonic boom and how quiet is quiet enough.”

One of the flavors Gulfstream has developed is the Quiet Spike, a three-segment composite structure that telescopes out from an initial length of 14 ft to a fully deployed 24 ft. Each of the three segments is designed to set up a very weak shock. Flight testing for the spike on an F-15B ended earlier this year, and it behaved structurally just as Gulfstream engineers predicted, according to Henne. The testing was not designed to produce a sound signature on the ground because, he noted, “the F-15 is a flying brick, and it consumes anything that is set up in front of it” in terms of noise. Near-field signatures were captured by tankers flying below the F-15, and results aligned tightly with Gulfstream engineering predictions.

 “There are some next-generation activities that we are contemplating,” he said of the Quiet Spike. “And there is regulatory effort under way to a rational sonic boom rule, as opposed to a prohibition.”

Once Gulfstream or some other company develops technology that allows for quieter supersonic flight, the government likely will adopt rules to accommodate it. Henne said he is confident that, at that point, the market for supersonic business aircraft will develop.

Supersonic flight is envisioned by Gulfstream in the form of an eight-passenger aircraft with maximum mass of 100,000 lb, takeoff field length of 6000 ft, range of 4800 nmi, and cruise speed of 1.8 M. By comparison, Henne noted, Gulfstream’s eight-passenger, 91,000-lb top-of-the-line G550 has a cruise speed of 0.80 M and a range of 6750 nmi. A key to success in supersonic flight is the ability to take off and land the plane at the same fields that accommodate current Gulfstream planes, he added.

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