Northrop, DARPA to demonstrate autonomous UAV refuelling

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Northrop Grumman dropped out of the US Air Force tanker race nearly four months ago, but a new contract award revealed shows they remain in the aerial refuelling market.

In fact, Northrop plans to go one better than manned aerial refuelling - the aerospace giant is now working with the US Defense Advanced Research Projects Agency (DARPA) on autonomous high-altitude refuelling.

Under a $33 million deal dubbed KQ-X, Northrop will demonstrate refuelling with a pair of Block 10 RQ-4 Global Hawks the company is currently sharing with NASA.

The ability to refuel in mid-air without the aid of a pilot on the ground would extend the Global Hawk's time on station from 30h to 35h to a matter of days, Gamache says.

global hawk refuelling, nasa 
 © NASA

"By getting rid of the pilot, we're exceeded the limits set by human biology. Now we are set to remove the limits of fuel. From there, the Global Hawk's limitations will become a matter of system reliability and payloads," he said.

The programme will bring together Northrop, DARPA, NASA and the National Oceanic and Atmospheric Administration to retrofit two Global Hawks for an entirely autonomous hose-and-drogue refuelling system.

The receiving aircraft will be fitted with a 4.3m (14ft) probe and the "tanker" drone will get a hose and drogue system installed in its nose, where the synthetic-aperture radar usually resides.

For now, the refuelling attempt will be on the centreline using GPS and an optical tracking system to make connections and transferring fuel between the fuselage tanks, says Mark Gamache, Northrop's director of advanced programmes and technology.

"Once we prove the technology, then we'll maximise the amount of fuel that can be transferred in and out of wing tanks on both birds," he said.

The programme will also mark the first attempt to fly Global Hawks in formation, according to Northorp.

Because the Global Hawk can fly at altitudes up to 65,000ft (19,800m), refuelling will take place at a much higher altitude than has previously been demonstrated with manned aircraft. Most aerial refuelling takes place around the 20-30,000ft range, depending on the platform.

KQ-X will build on work already done by DARPA and Sierra Nevada at NASA's Dryden Flight Research Center outside Palmdale, California, where the Global Hawk is assembled, Gamache says. During the Autonomous Airborne Refueling Demonstration project, a NASA-owned Boeing F/A-18 made contact with a Boeing 707-300 tanker 18 times; the programme concluded in 2007.

"We've been working with DARPA for quite a while to get to where we're at with this contract award," he says, citing October 2008 as the date of Northrop's original proposal to DARPA.