Solar Plane Completes First Intercontinental Flight

Sun-Powered Shadow

The unique silhouette of the experimental aircraft Solar Impulse soars above Rabat, Morocco, just before landing to complete an unprecedented intercontinental journey—without fuel tanks.

The plane touched down in the North African capital at 11:30 p.m. local time, 19 hours after take-off from Madrid, Spain, with Bertrand Piccard, one of the aircraft's two designers, in the cockpit. The 448-nautical-mile (830-kilometer) flight across the strait separating Europe and Africa, put Solar Impulse into the history books as the first manned solar intercontinental flight.

"The flight over the Gibraltar strait was a magical moment, and represents one of the highlights of my career as an aeronaut," said Piccard after deplaning before a cheering crowd at Rabat-Salé international airport.

It was the second part of a two-stage trip from the plane's base in Switzerland. The plane had been holding at Madrid for more than week waiting for calm weather, after originally taking off from Payerne, Switzerland, and flying 17 hours into Spain with Piccard's project partner and codesigner, André Borschberg, as pilot.

This jaunt is a warm-up for the Solar Impulse's planned round-the-world flight in 2014.

Night Preparations

Solar Impulse's ground crew can be seen making final preparations for takeoff in the wee hours of the morning—at 5:22 a.m. Madrid time on June 5. The intercontinental leg of the solar plane's journey was delayed several days by weather, though not by a lack of a sun. High winds, which create problems for the ultralight craft, kept the plane grounded until conditions improved early this week.

Once under way, the flight to Morocco took 19 hours and 8 minutes at an average ground speed of just under 32 miles per hour (52 kilometers per hour). Although it began and ended in darkness, the flight didn't really tax the airplane's power sources. "After almost 20 hours of flight we landed with a full set of batteries," said pilot André Borschberg. "This is extraordinary as it represents an increase in confidence in new technologies."

Crossing a New Frontier

Powered only by the sun above its wings, Solar Impulse soared to heights of 27,000 feet (8,229 meters) while en route to Morocco, where its international journey ended. The team said that the flight was made "under the patronage" of Morocco's King Mohammed VI, and by invitation of the Moroccan Agency for Solar Energy (MASEN). The team chose Morocco as its destination in order to help launch construction of the world's largest (160-megawatt) solar thermal power plant.

A Flight by Light

The Solar Impulse aircraft stands on the airfield in Payerne, Switzerland before a test flight last year. Solar flying takes patience and a wait for favorable conditions, but the team had confidence that the skies would be right for its late-spring history journey.

"Weather isn't a reliable science but we always find a window," Solar Impulse spokesperson Alexandra Gindroz said.  "It isn't about rushing or completing the flight at some speed. It's about having good conditions."

"Solvay," the word displayed prominently on Solar Impulse's nose, is an international chemical company that became the project's first major partner in 2004, and contributed high-performance ultralight polymers that made the physical construction of the aircraft possible. Other sponsors include the watchmaker OMEGA, Deutsche Bank, and Schindler, a leading provider of elevators and escalators.

Stretching Its Wings

A record-breaking journey began when Solar Impulse took off from an airfield in Payerne, Switzerland, en route to Madrid, Spain, on May 24. André Borschberg, the project's chief executive officer, flew the first leg of a 1,550-mile (2,500-kilometer) intercontinental flight that ended in Rabat, Morocco, without using a drop of fossil fuel or emitting any pollution.

Waiting for Calm

Much like the aviation pioneers of the early 20th century, the pilots of the Solar Impulse must wait for the right weather. The aircraft is seen here in April 2011 at its hangar in Payerne, Switzerland.

Aircraft Array

The carbon-fiber Solar Impulse aircraft has an enormous 200-foot (61-meter) wingspan—similar to that of an Airbus A340.

Yet it's ultralight, weighing only about as much as an average automobile (3,525 pounds or 1,600 kilograms). Almost 12,000 silicon solar cells, most arrayed on the aircraft's wings, drive four electric motors that can turn the plane's propellers day or night thanks to power-storing batteries.

Sky-High Energy Storage

Solar Impulse soars above Montreux, Switzerland, in a 2010 test flight. The plane's batteries store solar energy to make night flight possible but they also presented one of the aircraft's great engineering challenges. The batteries weigh approximately 880 pounds (400 kilograms), more than 25 percent of the plane's total mass, and necessitated major weight reductions across the rest of the body.

Propelling a New Era of Flight

Rammos Lyssandre, an aircraft designer who interned with Solar Impulse for his master's thesis in 2008, tests one of Solar Impulse's four propellers. The propellers drive the 71.5-foot-long (21.8-meter-long) aircraft at average flying speeds of 43.5 miles per hour (70 kilometers per hour). The plane's four motors average 8 horsepower, and together produce about the same amount of power as the Wright brothers used on their famous flights in 1903.

Breaking Records, Day and Night

Solar Impulse sits on the runway in Payerne, Switzerland, on the morning of July 8, 2010, after the 26-hour flight that was the first night flight in the relatively short history of solar aviation.

Before the flights this spring, the plane already held three world records; absolute height (30,300 feet, 9,235 meters), height gain (28,688 feet, 8,744 meters) and duration for a manned solar flight (26 hours, 10 minutes, 19 seconds).

Circling Not a Problem

Solar Impulse prepares to land in Brussels, Belgium, at the tail end of its first international flight in May 2011. That flight originated in Switzerland.

When André Borschberg reached Madrid late last month, after a far longer flight and some 14 hours aloft, his landing was postponed but demonstrated another advantage of solar flight. "We had to wait like three hours for authorization to land, so that all the regular traffic could land," Gindroz said. "But it's not a problem for us to circle because Solar Impulse doesn't have any limitations with fuel."

Airborne Without Contrails

Solar Impulse, an unusual entrant in the race for green transportation, takes to the skies above Payerne, Switzerland, on May 24. Some 17 hours later the sun-powered plane had traversed the Pyrennees and landed in Madrid without consuming a drop of fuel or creating any emissions. The flight is meant to fire the imagination and showcase the potential of solar powered flight in an aviation industry currently dominated by powerful fossil fuels.