It took me a few seconds to work out which way up this one is. It's the US Naval Research Laboratory's XFC experimental fuel cell unmanned aircraft, a rail-launched, folding-wing, expendable UAV that exceeded 6 hours endurance during a flight in early June. In its final form, says NRL, the XFC will loiter at 30kt and dash at 52kt.

Photos: NRL

The pusher-propeller XFC appears to have two pivoting wings, one on top and one of the bottom, shaped like hockey sticks with winglets attached to the handle - the top one pointing down and the bottom one up. The payload ball is under the nose. The hydrogen fuel-cell powerplant is supplied by Protonex.

XFC will be on show at next week's AUVSI show in Washington, along with the vehicle below - Israeli company BlueBird Aero Systems' more conventional-looking Boomerang, a 9kg UAV said to have an endurance exceeding 9 hours on the power of a 2kg, 900Wh powerplant from Singapore's Horizon Fuel Cell Technologies.