Defense Technology International - June 2008 - (Page 18)

DISPATCHES LOCKHEED MARTIN GLOBAL New stealth technology applied to a ﬂying wing will yield low RCS levels. a surprise when an early-2006 high-level Pentagon review killed it, splitting resources into a white-world Navy effort and a classiﬁed USAF program, while endorsing a plan to ﬁeld a bomber in 2018. It’s now apparent, however, that USAF had already picked a primary approach to the NGB, and that the next two years of work, starting with the remaining Fiscal 2006 JUCAS funding, are intended to validate that choice. This approach emerged from J-UCAS, and particularly from Northrop Grumman, which anticipated the J-UCAS split and was prepared to respond. The company believed that the basic 42,000-lb. J-UCAS was better suited to the Navy than to USAF, had focused on the carrierbased J-UCAS demonstration and picked a design that o ered high lift and a simple wingfold. Northrop Grumman’s proposal for a bigger X-47C also preceded—and may have inspired—USAF’s switch to a larger longrange bomber. This meant, too, that the NGB program could get a running start because it would use aerodynamics and stealth technology that were in the works for J-UCAS. The X-47B was much more advanced, in aerodynamic terms, than it appeared (see sidebar), and the same is likely true of its low-observable (LO) qualities. The aircraft is one of the ﬁrst to combine a highly blended tailless conﬁguration with new materials developed since the 1980s. The NGB will be the same, if not more so. Northrop Grumman has stressed the “all-aspect, broadband” stealth inherent in the X-47B. Tailless shapes don’t have the “bow-tie” RCS pattern, with the smallest RCS on the nose and tail and peaks on the beam conﬁgurations, which characterizes conventional aircraft. They are stealthier against lowfrequency radars—including updated, active-array VHF radars marketed by Russia—because they do not have shape features which are so small that their RCS in the VHF band is determined by size, rather than shape or materials. It may be significant that John Cashen, leader of the B-2 signatures team, returned in 2006 after 10 years in Australia and is now a consultant for Northrop Grumman. RCS test facilities across the U.S. have been upgraded since the F-22 and B-2 were designed: USAF’s range at Holloman AFB, N.M., was reequipped to handle bistatic measurements, and a sophisticated airborne RCS measurement program based on a modiﬁed 737 was delivered in 2001. How low can LO go? One paper, coauthored by a principal in DenMar Inc., the company founded by Stealth pioneer Denys Overholser, refers to the development of fasteners for a body with an RCS of -70 dB./sq. meter—one-thousandth of the -40 dB. associated with the JSF, and one-tenth that of a mosquito. DTI queried RCS engineers who don’t believe such numbers are possible; but then, when mention of a -30 dB. signature leaked out in a 1981 Northrop paper, nobody believed that either. I HIGH FLIGHT, LONG RANGE The NGB has been described as having a 2,000-naut.-mi. range and 14,000-28,000-lb. weapon load, a combination that could be met by an aircraft resembling a scaled-up X-47B that’s about half the size of a B-2. Northrop Grumman has advocated blended-wing-body aircraft shapes based on a simple kite-shaped planform. The X-47A Pegasus, unveiled in 2001, was a pure kite, while the X-47B is a “cranked kite” with extended outer wings. Similar conﬁgurations have been shown in studies for manned and unmanned bombers and SensorCraft, a USAF project for a high-altitude, long-endurance UAV. Northrop Grumman aerodynamicist 18 Barnaby Wainfan describes the X-47B as “revolutionary” in efficiency and handling. The aircraft is “more like a sailplane than a bomber.” Program leader Scott Winship says that the X47B meets carrier-landing standards without complex high-lift devices. One key to X-47B performance (and by extension the new bomber) will be the ability to maintain laminar flow over its lifting surfaces. Doing this over a long-chord wing with overwing inlets has been a problem, but a combination of high-precision manufacturing and high-power computational fluid dynamics techniques may have solved it. Also important to the cranked kite are ﬂight controls, which combine inset surfaces above and below the kite with simple hinged surfaces on the wing. The new shapes appear to provide enough authority and gust response with smaller and lighter surfaces (with smaller actuators) than were needed on the B-2. Improved controls in SensorCraft also provide enough authority for stable high-altitude ﬂight, a problem for earlier ﬂying wings. One advantage of the cranked kite over older ﬂying wings is that the centerline is long, which makes room for a large weapon bay and LO engines; a scaled X-47B configuration would be almost as long as a B-2. Weighing about as much as a Boeing 737, the prototype would be the right size for two non-afterburning versions of Pratt & Whitney’s F119/F135 family, drawing on inlet and exhaust technology developed by P&W for the X-47B. I AviationWeek.com/dti DEFENSE TECHNOLOGY INTERNATIONAL JUNE 2008 http://AviationWeek.com/dti

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Defense Technology International - June 2008 Contents Around the World Science Watch Tech Watch Basic Black Self-Defense Fire-Resistant Perfezione Hyperspeed Trial Big Sky Cashing In Digital Links Hang Ten Sea Change Programs Update Two Steps Back Direct Hit Staying Power Potent Stinger Do No Harm Guard Duty The Net Cutting Edge First Person In Review Insight

Defense Technology International - June 2008

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