Solar plane completes first 24-hour flight

Plane that took off from Switzerland meets goal of staying aloft for 24 hours by flying at night with solar energy captured during the day.

Lance Whitney Contributing Writer
Lance Whitney is a freelance technology writer and trainer and a former IT professional. He's written for Time, CNET, PCMag, and several other publications. He's the author of two tech books--one on Windows and another on LinkedIn.
Lance Whitney
3 min read
The Solar Impulse takes to the skies for its longest attempted flight yet. SolarImpulse.com

A solar-powered plane designed to fly both day and night has succeeded in its first attempt at a 24-hour voyage.

Taking off from its base in Switzerland, the Solar Impulse HB-SIA soared into the sky at 6:51 a.m. Wednesday local time (9:51 p.m. Pacific time Tuesday), intent on staying in the air nonstop for 24 hours by flying through the night powered purely by the solar energy captured during the day.

"24 hours and a successful flight through the night!" read a post on the Solar Impulse Twitter feed posted at around 9:38 p.m. PDT Wednesday. "This is a milestone in putting fossil fuels behind us."

Solar Impulse aircraft flies, briefly (photos)

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The Solar Impulse site tracked the progress of the pilot, Andre Borschberg, and outlined the itinerary and hopes for the entire flight. The plan was that the Solar Impulse would slowly attain an altitude of nearly 28,000 feet with the sun's rays both powering the propeller plane and charging its batteries to prepare for the night flight.

As the sun started to sink too low to continue providing energy to the solar cells (about two hours before sunset), Borschberg planned to begin a slow descent, hitting an altitude of around 4,900 feet by 11 p.m. local time. The goal at that point was to continue flying throughout the night and until the next sunrise using only the captured energy stored in the plane's batteries. The question was whether Borschberg could coax the batteries to supply enough juice to keep him aloft all night before landing at dawn on Thursday.

"Goal achieved for SI. Historic moment. Jubilation here in Payerne, Switzerland!" read another tweet posted Thursday night on the Solar Impulse Twitter page. Solar Impulse is calling the flight the longest and highest flight completed by a solar plane.

The Solar Impulse team originally planned the first 24-hour flight for last week. But a technical glitch with the telemetry transmitter, which lets the ground crew monitor the flight, kept the plane grounded until the problem was resolved.

The public can follow the flight and aftermath via the site's dedicated page, its blog, and its Twitter feed.

Photos: Soaring ambition for solar aircraft

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The saga of the Solar Impulse began seven years ago when a team of 70 designers, engineers, and other specialists gathered to create the first prototype of such an aircraft.

Unveiled a year ago, the Solar Impulse HB-SIA took off for its first test flight in December before embarking on its first official maiden voyage in April and a series of other flights in May.

The next step will be to cross the Atlantic in 2011 in a new, lighter prototype plane dubbed the HB-SIB, followed by an around-the-world trip in 2012.

"The goal of the project is to have a solar-powered plane flying day and night without fuel," team co-founder Bertrand Piccard said in a statement. "This flight is crucial for the credibility of the project."

Update 12:47 p.m. PDT: Daylight hours are winding down in Swiss air space as the HB-SIA passes 14.5 hours of flight time. Pilot Borschberg has been asked to shut down all of the aircraft's solar power generators.

"This comes at a perfect time because here in Switzerland, the sun is setting," reads an update on the Solar Impulse site. "André is now coasting and awaiting clearance to fly on where only owls and bats dare. Stay tuned. It's coming soon. Real soon."

Update 9:46 p.m. PDT: The top of the story was recast to show that the Solar Impulse HB-SIA has completed its 24-hour flight.