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Who Is Sponsor of Skunk Works' SBJ Project?
Famous for secrets, Lockheed Martin's Skunk Works is still masking the identity of the sponsor behind its supersonic business jet (SBJ) project. Suspect number one, multibillionaire NetJets owner Warren Buffett, says it's not him - although NetJets continues to be a booster of the project. Lockheed Martin has stopped granting interview requests, and has imposed gag orders on partners such as engine manufacturers.
Lockheed Martin (Chalet D10-11 and OE15) briefings and documents - including a voluminous patent from low-sonic-boom guru John Morgenstern, released in May - paint a picture of a large program that may be further advanced than competitors claim to be. In a presentation to a Federal Aviation Administration conference late last year, Lockheed Martin bluntly described its SBJ design as "closed" and its certification basis as "developed," stressing that the aircraft will have a simple engine and conventional construction.
Unlike other manufacturers who briefed the same meeting, Lockheed Martin did not say that an X-plane program would be a prerequisite for the launch of a commercial program. All that is needed, the company says, is a rule allowing supersonic flight overland with a quiet boom profile and a 0.5 psf peak overpressure. Significantly, too, General Electric and Pratt & Whitney - both supporting the Lockheed Martin project - said in their presentations that an SBJ could enter service as soon as 2010.
Morgenstern's patent included a variety of configurations, but the dominant shape - also used in the FAA briefing – is an arrow-winged twin-jet, 130 feet long with a 55-foot span, and weighing around 130,000-140,000 pounds at take-off. The cabin looks to be in the same class as a super-midsize jet like the Challenger 300. SBJ advocates have pointed out that an airplane with a three-hour flight time does not need a Gulfstream-size cabin.
The engine manufacturers' presentations point to a 4,000 nmi range and a cruise speed of Mach 1.8 or less - the latter makes it easier to achieve noise, efficiency and durability targets compared to the Mach 2 Concorde. Lockheed Martin says that the aircraft would meet Stage IV noise rules with simple inlets and a conventional turbofan engine, and will use "conventional, low-cost" metallic construction.
The Lockheed Martin SBJ's most striking feature is a "tail-braced wing." The swept wing is braced to the fuselage by an inverted-vee, forward-swept tail and a stumpy vertical stabilizer that also connects to the underwing engine nacelles. This not only stiffens the wing - which would otherwise be too flexible to carry the engines - but forms part of a low-sonic-boom treatment that uses shock cancellation, deliberately creating a pressure rise, opposite and equal to a pressure drop, to soften the boom. Other low-boom features include an upward-cambered nose, and upswept wings that expand the pressure wave laterally.
Whether the project goes ahead depends on money. So far, Palmdale's
benefactor has paid for business studies, research and preliminary
design, but there is no sign that he is ready to pop for the several
large ones required for development and certification. As GE's advanced
engine design leader, Harvey Maclin, put it earlier this year, "The
technology is great but we don't have the resources to accomplish
it." But he added, "This year should be interesting."
- Bill Sweetman
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