Hydrogen powered hybrid stratocraft prangs during test flight

Special-ops comms bird built for a week 12 miles up

A radical new prototype hydrogen-powered high altitude robot aircraft, intended to remain airborne for a week at a time, has crashed during a test flight in California.

The Global Observer drone, which had taken off 18 hours previously from Edwards airforce base, was lost at 2:30pm local time on Friday. It was the aircraft's ninth test flight in a technology-demonstration programme intended to prove endurance of at least five days cruising at 65,000 feet.

"Flight testing an innovative new solution like Global Observer involves pushing the frontiers of technology and convention," said Tim Conver, CEO of famous crazy-planes firm AeroVironment, manufacturer of the Observer. "Risk is a component of every flight test program."

The Global Observer was being developed for various US government bodies, including the military special-operations command. It was expected to be able to remain on station 12 miles up above battlefields, with only small numbers of aircraft based safely far away able to maintain constant patrols. It would have carried communications equipment able to provide high-bandwidth services to small, portable ground terminals using compact antennae.

At the moment US special ops teams or others far from groundbased wireless coverage must typically accept rubbish bandwidth or set up a bulky, inconvenient satellite antenna, or arrange for an expensive conventional comms aircraft on station overhead, a commitment which means tying up a lot of planes and personnel. Thus the capability offered by the Global Observer and its various rivals (other high-altitude hydrogen planes, dirigible sperm-ships etc) remains highly desirable.

The Global Observer was expected to achieve excellent high-altitude performance and long endurance by its use of electrically-driven propellors hooked up to a battery supplied by a generator. This generator was driven by an internal-combustion engine running on hydrogen.

The electric transmission is a signature method for AeroVironment, which has built many other electrically-propelled aircraft. The Global Observer's rival in the 65,000-foot drone arena, the Phantom Eye from Boeing, uses two slightly modified turbocharged Ford Fusion car engines running on hydrogen: but these drive the props directly. The Phantom Eye is only expected to offer four days' endurance, as compared to a probable seven for the hybridised Observer.

No details on the problems which caused the Observer to crash are yet available. Another Observer prototype has been built and might proceed with testing, but AeroVironment admits that most of the project's funding has already been spent. ®

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