On a wing and a fuel cell
An unmanned aircraft capable of staying airborne for up to two weeks is to be developed by Boeing for the US military.
The unmanned aerial vehicle (UAV) will be powered by a hydrogen fuel cell and could be ready for take-off by 2004, according to George Muellner, director of Boeing's Air Force programmes.
It will be designed to carry out surveillance tasks, but could also be used as a temporary or emergency communications relay for civilian use. Muellner said it could operate like a very low earth-orbiting geosynchronous satellite. 'It would provide communications links, a cellular service net over a wide area. It would be up around 70,000ft and would remain airborne for two weeks,' he said.
A 15-strong team of engineers from Boeing's military and commercial divisions, plus staff from R&D wing Phantom Works, is working on the project in Washington and California.
However, Muellner, former head of Phantom Works, said that in conjunction with some European universities and companies Boeing has been researching fuel cell aircraft for some time.
A prototype project aimed at reducing engine acoustic noise is about to be tested in the Netherlands. 'They're trying to advance the state of the technology,' said Muellner.
Phantom Works recently opened a European centre in Madrid, which is also involved with the project. The prototype is expected to fly some time next year.
The initial design for the UAV's wingspan will be 35-45m, said Muellner. But the key to its success will be adapting fuel cell technology for flight. 'As we move to more electric aircraft what you're really looking for is something that can generate electrical power, and obviously fuel cells are a very efficient way of doing that. Our hope is to be able to move that to a plane that can stay up for upwards of two weeks.'
Work is already underway to develop lightweight storage tanks to keep hydrogen under pressure for long periods of time and drive down the aircraft's weight.The Boeing project is not alone, however. A smaller-scale project funded by US non-profit making organisation the Foundation for Advancing Science and Technology Education is focused on a manned fuel cell plane.
An all-carbon Lafayette III aircraft is being converted from internal combustion to electric propulsion in three stages. The first flights will use lithium-ion batteries. These will later be augmented by a fuel cell before switching to total fuel cell power.
Another possibility is the CarterCopter gyroplane, which uses a rotor for vertical take-off and landing and a small wing for normal flight.