GRAHAM WARWICK / WASHINGTON DC
Business jet manufacturer believes X-plane is key to development of QSJ concept
Successful development of a supersonic business jet will require a flight demonstrator, says Gulfstream, to validate sonic-boom suppression technology and convince regulatory authorities that supersonic overland flight is acceptable.
Where the money for an X-plane-type demonstrator will come from is far from clear, however, says Pres Henne, senior vice-president, programmes, engineering and test.
The US business jet manufacturer is continuing to refine its conceptual design for the Quiet Supersonic Jet (QSJ) - a Mach 1.8, 8,900km (4,800nm)-range aircraft with a Gulfstream II-size cabin and, now, a variable-geometry wing (Flight International, 5-11 August). The company has windtunnel-tested models that have validated boom-suppression design concepts, but believes a flight demonstrator is fundamental if the programme is to proceed.
"An X-plane is really key before any decision [on launching a supersonic business jet programme]." says Henne. "We need it to demonstrate to ourselves that we have boom suppression technology good enough to bring to market. The regulatory authorities need it too, to convince them we can do low boom and enable them to write a rational sonic boom rule." Supersonic overland flight, presently illegal, is essential for market acceptance, studies show.
Henne believes a supersonic business jet can only be developed after a low-boom demonstrator has flown successfully. "We have been pursuing the idea with NASA and DARPA [Defense Advanced Research Projects Agency]. The problem is the military side is not sure they need to worry about boom suppression, and the NASA side has so many priorities and so little funding. It's a struggle to see where a demonstrator is going to come from."
Under DARPA's Quiet Supersonic Platform programme, Northrop Grumman is flight testing boom suppression through airframe shaping using a modified F-5 (Flight International, 5-11 August). Programme manager Charles Boccadoro also believes the USA needs to fund an X-plane-like supersonic demonstrator to pave the way for a next-generation long-range strike aircraft.
Source: Flight International
