Pictures: Solar Plane Completes First Intercontinental Flight

Night Preparations

Photograph courtesy Jean Revillard, Solar Impulse

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."

Published May 31, 2012

Crossing a New Frontier

Photograph courtesy Jean Revillard, Solar Impulse

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.

"We share a common message with Solar Impulse, a strong one," said Mustapha Bakkoury, MASEN's president. "Solar energy (is) no longer restricted to the scientific world but is becoming an integrative part of daily (life). We will begin production in 2014, coinciding with Solar Impulse's world tour."

Published May 31, 2012

A Flight by Light

Photograph by Dominic Favre, European Pressphoto Agency

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.

Published May 31, 2012

Stretching Its Wings

Photograph by Laurent Gillieron, European Pressphoto Agency

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.

Borschberg described the flight as "incredible," adding: "This confirms our confidence in the capacity of solar energy even further."

Published May 31, 2012

Setting Sights on History

Photograph by Denis Balibouse, Reuters

Solar Impulse president Bertrand Piccard, who piloted the second leg of the Solar Impulse flight from Madrid to Rabat, Morocco, is seen preparing for a test flight in April at the project's base in Payerne, Switzerland.

(Follow the journey of Solar Impulse on the project's website.)

Published May 31, 2012

Waiting for Calm

Photograph by Denis Balibouse, Reuters

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.

"You know the airplane is very light and very sensitive to turbulence and strong winds," Gindroz said. Takeoff conditions are particularly important. "There are very low limitations for takeoff, between four and seven knots, so it's important that there is almost no wind at takeoff. In flight, we can afford a bit more wind."

Published May 31, 2012

Aircraft Array

Photograph by Francis Demange, Gamma-Rapho/Getty Images

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.

Published May 31, 2012

Sky-High Energy Storage

Photograph by Fabrice Coffrini, AFP/Getty Images

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.

Published May 31, 2012

Propelling a New Era of Flight

Photograph by Francis Demange, Gamma-Rapho/Getty Images

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.

Published May 31, 2012

Breaking Records, Day and Night

Photograph by Denis Balibouse, Pool/European Pressphoto Agency

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).

Published May 31, 2012

Virtual Reality, Vertical Peaks

Photograph by Francis Demange, Gamma-Rapho/Getty Images

Bertrand Piccard tests a virtual flight simulator in which he spent 25 straight hours preparing to pilot Solar Impulse on future long-distance flights without liquid fuel.

Solar aviation launched in the early 1980s when experimental flights first crossed the English Channel and then stretched out to distances of several hundred kilometers. In 1990, the Sunseeker crossed the United States in a series of almost two dozen stages, the longest of which was 250 miles (400 km).

Unmanned drones have already achieved some stunning solar successes as well. QuinetiQ's Zephyr drone flew nonstop for 14 days in July 2010, circling the skies above the Yuma Proving Ground, a U.S. Army test facility in Arizona. QuinetiQ officials said the plane might have kept flying indefinitely but had little else to prove.

Published May 31, 2012

Sizing the Challenge

Photograph by Francis Demange, Gamma-Rapho/Getty Images

The Solar Impulse team tests an early cockpit mock-up in July 2005. Conditions can be cramped but the plane isn't designed for practical transportation. It's an inspiring example of what clean, green technology is capable of achieving.

"Our airplane is not designed to carry passengers, but to carry a message," said Bertrand Piccard.

Published May 31, 2012

Circling Not a Problem

Photograph by Jean Revillard, Solar Impulse/EPA

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."

Published May 31, 2012

Pioneer Garb

Photograph by Denis Balibouse, Reuters

The suit and boots of Solar Impulse project CEO and pilot André Borschberg are shown before he took off from the airport in Payerne on May 24. Borschberg and his partner, fellow Swiss pilot Bertrand Piccard, spent seven years designing the aircraft.

Published May 31, 2012

Airborne Without Contrails

Photograph by Fabrice Coffrini, AFP/Getty Images

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.

Published May 31, 2012

Next: Quiz: What You Don't Know About Solar Power

Photograph by Michael Melford, National Geographic

Published May 31, 2012