NASA has built the spork of the skies. The GL-10 or Greased Lightning is a 28kg, battery-powered drone prototype that can switch between helicopter and airplane modes, giving the aircraft the maneuverability and vertical take-off capabilities of a chopper, as well as the speed and endurance of a plane. Although the GL-10's hover tests were reported last year, NASA says the craft has now made its first successful mid-flight transitions from helicopter to airplane-mode. "So far we have done this on five flights," said aerospace engineer Bill Fredericks in a statement. "We were ecstatic."

the GL-10 could be used for package delivery, mapping, and surveillance

The video above shows the carbon fiber GL-10 in action, with the craft's 10-foot wingspan holding eight rotors, while a further two are located on the tail. Fredericks says that the design for the GL-10 was originally twice as big and powered by a hybrid diesel / electric engine, but that a number of "hard landings" (aka crashes) encouraged them to scale things back. The current lightweight design could have a number of applications, say Fredericks. "It could be used for small package delivery or vertical takeoff and landing, long endurance surveillance for agriculture, mapping, and other applications. A scaled up version — much larger than what we are testing now — would make also a great one- to four-person-size personal air vehicle."

The GL-10 in the air. (NASA Langley/David C. Bowman)

The GL-10 on the ground. (NASA Langley/David C. Bowman)

The US military has previously experimented with similar hybrid designs in the V-22 Osprey, a tiltrotor craft (this mean that the rotors change orientation, rather than the wings, as with the GL-10) that can haul up to 32 troops hundreds of miles. However, the V-22 has also been a fairly controversial aircraft, with critics pointing to its less-than-stellar safety record, escalating costs, and perceived inability to function as well as a regular 'copter.