Solar plane sets out on historic flight

An experimental solar-powered aircraft took off from a Swiss airbase shortly after daybreak yesterday in a historic bid to fly around the clock and prove the value of solar energy.

Solar Impulse whirred along the runway at Payerne in western Switzerland, reaching 35 kilometres per hour as lone pilot Andre Borschberg gently lifted into clear skies at 6.51 a.m.

"Conditions are really beautiful up here, I feel great," Borschberg told AFP by radio some three hours into his planned 25 plus hour flight, as he cruised over the Jura hills in northern Switzerland at an altitude of 3,300 metres.

The Swiss pilot's take off run took barely 90 metres, testimony to the light weight and giant airliner-size wingspan of the single seater craft, which relies totally on 12,000 solar cells and nearly half a tonne of batteries.

"This should be a great day if all goes well," said team chief Bertrand Piccard, who made the first non-stop round-the-world flight in a balloon more than a decade ago.

"It's clear that this is something that is completely different at least for aviation, but it's also something completely different to what has existed in our society," he added.

"The goal is to take to the air with no fuel. The goal is to show that we can be much more independent from fossil energy than people usually think."

The ground control crew were due to decide shortly before dusk whether Mr Borschberg should press on with a pioneering flight through darkness and land at Payerne.

The go-ahead will depend on the sun's ability to charge up Solar Impulse's batteries in the daytime and the threat of strong high altitude winds, joint flight control chief and former astronaut Claude Nicollier said.

"We're confident the plane can do it," he added.

The overnight flight by the prototype built last year is the first major hurdle for the project since it started seven years ago, with the aim of flying around the world by 2013 or 2014. The Solar Impulse prototype relies on the sun to power the engines and charge the batteries, in theory storing enough energy to last through some seven to eight hours of darkness.

A first attempt was called off an hour before scheduled take off last Thursday after an electronic component failed, but it was replaced within days.

The single seater shaped like a giant dragonfly is clad with solar panels across a wingspan the size of an Airbus A340 airliner (63 metres).

But the high tech craft is powered by just four small electric motors and propellors - as the crew put it, the "power of a scooter" - and weighs little more than a saloon car.

The weight-saving has gone to the extent of saving on an automatic pilot for Mr Borschberg, a former fighter jet pilot, who will try to stay alert for up to 27 hours flight with the help of space mission-like ground control team.

Solar Impulse has completed at least 10 test flights since it first hopped along a runway seven months ago, staying aloft for up to 14 hours in the long summer daylight hours.

But the ultimate test will be to land back at Payerne shortly after dawn today having been fuelled by nothing but the sun's rays, setting the stage for ocean crossing, transcontinental and round the world flights over the coming years.

The pioneering bid is being monitored by the international aeronautical federation, which oversees aviation records.