US manufacturer close to first flight as pioneering unmanned air vehicle takes shape
Lockheed Martin plans to make the first attempt to fly a morphing unmanned air vehicle at Edwards AFB, California within the next two weeks and is hoping to conduct what is expected to be the first true in-flight configuration change next month.
The morphing UAV has been developed by Lockheed Martin's Skunk Works under a US Defense Advanced Research Projects Agency (DARPA) programme aimed at proving the viability of the concept and associated technologies. These include seamless skin materials, advanced flight-control software and smart-materials actuators.
Resembling the Boeing- and Northrop Grumman-built X-45/X-47 unmanned combat air vehicle demonstrators in overall pre-morphed configuration, the Lockheed Martin vehicle is designed to optimise its geometry to suit varying mission profiles. Taking off with wing extended to maximum span, the vehicle is designed to fold its wing inboard for higher speed low-level flight. Unlike swing-wing designs, the morphing concept involves tucking the inboard wing section up and flush with the fuselage. This results in a much larger reduction in wetted area, thereby significantly reducing drag.
"We get a 25% reduction in wetted area when we pull up the wings," says Lockheed Martin morphing aircraft programme manager Derek Bye. "We get an effective sweep change of 30û [measured at the 40% chord] when we fold the wings, even though the edges remain the same. When we unfold we get a 44% increase in maximum lift/drag ratio, and a 177% increase in effective span." In pre-flight test analysis the morphing design shows the potential for a "30-50% mission range increase over a typical hi-lo-lo-hi profile", adds Bye.
Displaying the second of two air vehicles at the Unmanned Systems North America convention in Los Angeles, Bye says the 2.75m (9ft) - span UAV represents a fifth-scale version of the full-scale morphing aircraft envisaged for possible service. Powered by a JetCatt P200 turbojet, the subscale version has a vertical tail that would be removed on the full-scale variant with the addition of a yaw-controlling thrust-vectoring system.
The company is mid-way through Phase II of the DARPA effort, which culminates with windtunnel tests at NASA Langley of a half-span model in June 2005. Phase III, if sanctioned, will cover development of a half-scale version for flight tests in the 2006-7 timeframe. A follow-on full-scale version would have a span of about 12.5m and require a 5,000lb-thrust (22.25kN) powerplant.
GUY NORRIS / LOS ANGELES
Source: Flight International
