There is a wrinkle to Northrop Grumman's plans to demonstrate the autonomous aerial refuelling of one Global Hawk by another at high altitude - the tanker will fly behind the receiver. The tanker will be equipped with a refuelling probe and the receiver with a hose-drum unit - the opposite of the normal probe-and-drogue arrangement - and it is the tanker that will rendezvous with the receiver, maneuver into contact with the basket and "push" fuel forward to the receiver. Northrop says this "reverse" refueling arrangement reduces the cost of equipping a Global Hawk fleet for aerial refueling because fewer...