SOARING silently above the barren flats of NASA’s Dryden Flight Center in California, Pathfinder is an extraordinary sight. No rudder, no tail, not even a fuselage. This pilotless aircraft is simply a flying wing 30 metres across and 2.5 metres wide. “From a distance it almost looks like a hawk soaring gracefully in the thermals,” says Nicholas Colella of Lawrence Livermore National Laboratory in California, who originally headed the programme that administered the Pathfinder project. Unlike the supersonic jets that roar above these testing grounds, Pathfinder carries no fuel. Instead, the elec tric motors that drive its eight propellers draw their power from the solar panels covering its wings (see Diagram).
Any solar-powered aircraft is impressive, but Pathfinder is the prototype for an even more ambitious craft, called Helios. Pathfinder can only fly when the Sun is in the sky. Helios will store enough energy during the day to keep it aloft at night, and so might never have to land. Engineers working on the project call it “the eternal airplane”.
So far, Pathfinder has been tested only at low altitude. Next week, researchers hope to test Pathfinder’s flight worthiness after recent modifications. If all goes to plan, in July, it will climb to 20 kilometres, where winds are relatively light. This is the altitude at which eternal aircraft will cruise on flights that could easily circumnavigate the globe. If all goes well, Helios could be flying within a year.
Eternal aircraft are more than a flight of fancy. AeroVironment of Simi Valley in California, the company that built pathfinder, says that these planes might take on many of…
