The Sun Plane

  • The Solar Impulse 2 in the middle of its first test flight on 2 June 2014, near Payerne, Switzerland.
  • Because the cockpit seats one, the plane will land every few days to change pilots.
  • Bertrand Piccard (left) and André Borschberg (right).
Date:13 May 2015

They’re the Amelia Earharts of clean energy: this month Swiss pilots Bertrand Piccard and André Borschberg will attempt to become the first people to circumnavigate the world in a solar-powered airplane. Their twelve-leg, 35 000 km trip will take five months to complete, beginning and ending in Abu Dhabi, with stops in North Africa or southern Europe and the United States. We had a few questions.

By Rachel Sturtz

Who are these guys?

Bertrand Piccard (above right) is an aeronaut who co-piloted the first nonstop trip around the world in a balloon in 1999. In 2003, he teamed up with André Borschberg (above left), an engineer and former fighter pilot. With a crew of eighty engineers and technicians, the two devoted the next twelve years to developing one of the most innovative solar-powered, machines on the planet.

Will this be their first attempt?

At travelling around the world, yes. There was an earlier prototype, Solar Impulse 1, that broke eight records, three of them when Borschberg flew it for 26 hours straight in the first night flight in the history of solar aviation. They’re now on to Solar Impulse 2, which has greater energy density in its 635 kg of lithium-ion batteries and improved 13 kW electric motors that spin the propellers with 94 per cent efficiency.

How comfortable is the plane?

Not very, especially considering that it is unpressurised and has no heat. Borschberg and Piccard will have oxygen tanks to deal with the altitude, but they’ll be forced to endure temperatures that fluctuate between -20 and -30 degrees Celsius with only small warmers for their hands and toes.

How do they sleep?

They don’t, really. Since only one pilot can fit in the three cubic metre cockpit at a time, he is allowed just six 20-minute naps a day while the plane is on autopilot. Both men have trained in meditation and self-hypnosis to rapidly enter deep sleep and wake up alert.

Is there a bathroom?

The longest and most demanding leg of the trip is a five-day stretch of continuous flight over the Pacific, so it wouldn’t be fair to expect the pilot to wait for a rest stop. The seat, which can recline completely for naps and physical exercise, also serves as a toilet – by removing the cushion of the seat as you might on a private plane.

If it’s a solar plane, does that mean it can’t fly at night?

The plane uses stored energy to fly in the dark. So as not to exhaust its reserves, Solar Impulse 2 takes advantage of gravity, gradually gliding down to an altitude of
1,5 km at night. During the day the pilot regains a cruising altitude of 8,5 km – where there is lower air density and drag — and can reach a top speed of 138 km/h while the batteries are recharged.

How big is this thing?

Solar Impulse 2
Wingspan: 72 m
Weight: 2 268 kg

Boeing 747-400
Wingspan: 64 m
Weight: 180 tons

Are they scared?

The plane has never flown in inclement weather or periods of turbulence. In case they do run into trouble, the two have been practising parachute landings and treading water in the North Sea. “If oxygen runs low, if there’s not enough energy to fly through the night, or if autopilot doesn’t work, we’ll end up in the water,” says Borschberg.

Okay, so what’s the point of all this?

Although Piccard admits that solar-powered commercial flights may never happen, “we would be able to cut the world’s energy consumption in half if we replaced old technology with current technology,” he says. They also hope to inspire more businesses to consider clean energy. They’ve already heard from companies that want to use their technology to replace satellites with cheap, unmanned aerial vehicles for transmitting telecommunication services to developing countries.