Friday, March 11, 2011

Seven-day flight proposed for Global Hawk

SOURCE ADMIN Northrop Grumman has revealed an internal goal to perform a seven-day, non-stop flight by the RQ-4 Global Hawk after completing in the second quarter next year an autonomous, high-altitude refuelling (AHR) demonstration.
The proposed endurance flight is aimed at proving that adding in-flight refuelling to a currently 30hr-endurance RQ-4 will beat a new class of potential rivals powered by liquid hydrogen fuel, such as the AeroVironment Global Observer and the Boeing Phantom Ray.
"That is the goal," says Jeff Summers, Northrop's programme manager for the AHR demonstration. "That's one of the strategic imperatives here is to demonstrate a reliably low-risk and low-cost approach to extending the range of a high-altitude [unmanned air vehicles]."
Summers described propulsion systems relying on advanced fuels as inherently risky compared to achieving ultra-endurance using autonomous, high-altitude refuelling technology.
"We see this as an alternative that builds upon existing technologies," Summers says.
The seven-day flight by the Global Hawk is not yet funded under the DARPA $33 million AHR programme, which was awarded to Northrop last July.
But the Global Hawk will be capable of performing the flight at the end of the funded programme, awaiting only DARPA's go-ahead and funding to launch the seven-day flight demonstration, Simmers adds.
For the AHR demonstration, Northrop is modifying two NASA-owned Global Hawks -- AV-1 and AV-6 - to serve as a tanker and a receiver. The AV-1 tanker will be equipped with a hose reel in the nose radome, with AV-6 equipped with a probe.
The two aircraft will rendevous with a Sierra Nevada guidance system using differential GPS and an optical tracker to guide AV-1's drogue into the AV-6 probe. The concept uses a reverse flow refuelling system, so the AV-1 tanker pushes fuel into the AV-6 flying up to 15m in front. Using this method requires Northrop to modify only a few tankers to manoeuvre in close formation with another unmanned system, Summers says.
Northrop plans to complete a series of autonomous dry engagements by the end of this year using the AV-1 and AV-2 Global Hawks. In the wet engagement flights next year, the AV-1 will offload 1,361kg (3,000lb), wait 3hr, then offload another 1,361kg, Summers says.
On 21 January, Northrop completed a flight simulating refuelling distances between the unmanned AV-6 Global Hawk receiver and the manned Scaled Composites Proteus operating as a tanker.

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