Air Transport

NextGen Aeronautics is to build a small unmanned air vehicle able to change shape in flight under the next phase of the US Defense Advanced Research Projects Agency’s (DARPA) morphing aircraft structures programme. The 90kg (200lb) autonomous vehicle will demonstrate NextGen’s morphing wing in flight.

Award of a contract for Phase 3 of the DARPA technology demonstration follows “enormously successful” windtunnel tests of a full-scale model of NextGen’s wing, says president Jay Kudva. The wing, which has an articulating lattice structure covered with a stretchable reinforced skin, was tested at speeds up to Mach 0.92 and “very high” dynamic pressures. The model demonstrated morphing from 15° to 45° sweep – wing chord and area changing by a factor of almost two – in just 10s, he says.

Torrance, California-based NextGen is under contract to fly the small twinjet UAV within nine months, says Kudva, with the goal of demonstrating flight control during simultaneous morphing and manoeuvring at speeds exceeding 175kt (320km/h). The UAV is a less expensive and lower risk step towards flying a 2,500kg, M0.9 demonstrator as a forerunner to an operational vehicle, he says.

DARPA’s goal is to demonstrate technology for an unmanned aircraft able to combine efficient loiter with high-speed dash by morphing the wing from high- to low-aspect ratio. NextGen’s wing morphs “in plane”, actuators moving the articulating structure in two directions to change not only sweep, but chord, span and area. Lockheed Martin tested an “out of plane” morphing concept in which the wing folds upwards and inwards against the body, reducing span while increasing sweep.

In NextGen’s windtunnel model, about 60% of the wing was flexible, its articulated skeleton driven by nine actuators. The leading and trailing edges, including control surfaces, were fixed to the lattice structure, but able to move as the wing morphed between unswept and fully swept. The small UAV will have fewer actuators for ease of manufacture.

Kudva says NextGen is looking at commercial aircraft applications of its technology, including morphing winglets and noise-reduction features. The company is also working on vehicle health-monitoring systems and conformal load-bearing antennas. “What we are heading towards is the cognitive aircraft: one that can sense, heal and change shape. Morphing is one piece,” he says.