The solar powered plane Solar Impulse has begun its first 24-hour test flight, aiming to make it through the night on power collected during the day.
The plane took off from the Payerne airfield in Switzerland at 1.00am EST. "That’s it! The solar big bird is in the air, and we hope it’ll stay there until tomorrow morning," says team member Lucas Chambers on the mission blog.
He says visibility is expected to be poor at first, but 'spiffy' in the afternoon - and, most importantly, through the night.
Piloted by former jet pilot Andre Borschberg, the plane has an 80 meter wingspan and weighs just 1,600kg. Nearly 12,000 solar cells power the four 120-horsepower motors and polymer lithium batteries.
The advantage of a summer flight is the longer daylight hours, and the team had hoped to make the test flight even closer to the solstice. However a communications problem delayed the flight by a week. it means that if this trip fails, the team will have to wait until next summer to try again.
The flight is expected to last 25 hours, with the plane reaching an altitude of around 8,500 meters. Tonight, as darkness falls, Borschberg will decide whether to carry on through the night on battery power.
The team is headed by round-the-world balloonist Bertrand Piccard. Shortly before takeoff, he reminded the team, "This airplane is here to prove that renewable energies are not just pornography for tree huggers."
Solar Impulse was completed last year, and has carried out ten daylight test flights since. This will be its longest trip yet. The trip is a preparation for an Atlntic crossing next year and - if that's successful - a multi-leg global circumnavigation in 2013.
You can watch the flight live, here.