High-altitude autonomous refuelling is put to the test

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Autonomous aerial refuelling between two unmanned aircraft has moved a step closer following a test flight conducted in the US.

In a risk-reduction flight test, Northrop Grumman’s Proteus test aircraft and a NASA Global Hawk flew as close as 40ft apart at an altitude of 45,000ft.

The flight test was conducted at the high-altitude environment required for the refuelling of high-altitude, long-endurance (HALE) unmanned aircraft systems (UAS).

Wake turbulence between the two aircraft, as well as engine performance and flight-control responsiveness in the stratosphere, were evaluated. Simulated breakaway manoeuvres were also conducted.

The flight, which took place on 21 January, was key to reducing risks as the programme between Northrop Grumman, Defence Advanced Research Projects Agency (DARPA) and NASA Dryden Flight Research Centre prepares for autonomous aerial refuelling of two Global Hawks in the spring of 2012.

‘Demonstrating close formation flight of two high-altitude aircraft, whether manned or unmanned, is a notable accomplishment,’ said Geoffrey Sommer, KQ-X programme manager at Northrop Grumman Aerospace Systems sector. ‘When you add autonomous flight of both aircraft into the mix, as we will do later in the KQ-X programme, you gain a capability that has mission applications far beyond just aerial refuelling.’

The $33m (£20.4m) DARPA KQ-X programme will demonstrate autonomous fuel transfer between two Global Hawks, enabling flights of up to one-week endurance.

KQ-X is a follow-on to a 2006 DARPA Autonomous Aerial Refuelling Demonstration (AARD), in joint effort with NASA Dryden, which used an F-18 fighter jet as a surrogate unmanned aircraft to autonomously refuel through a probe and drogue from a 707 tanker.