Bertrand Piccard and André Borschberg will take turns piloting the single seater Solar Impulse 2 plane that is propelled solely by the sun

A Swiss pilot has begun the first ever attempt to fly around the world in a plane propelled only by the sun.

André Borschberg and his compatriot Bertrand Piccard will take turns piloting the single seater Solar Impulse 2 for 21,747 miles (35,000km) over 12 legs, including gruelling five- to six-day stints across the Atlantic and Pacific oceans. The entire journey will take five months.

Borschberg took the controls for the takeoff at Al-Bateen executive airport in Abu Dhabi early on Monday. Its first destination is Muscat in Oman.



The pilots will endure roughly 250 hours each inside a narrow cockpit with no oxygen or temperature control. Temperatures outside will range between -40C to 40C.

Pilots Bertrand Piccard and André Borschberg Photograph: PR

Falling asleep for long periods will be impossible as the flight will need constant attention. Piccard and Borschberg will survive on 20-minute naps every two to four hours.

The pilots will practise yoga to stave off the physical discomfort of remaining confined to a seat for days at a time. But Borschberg said the biggest challenge was maintaining concentration.

Piccard, who is a psychiatrist as well as being part of the team that in 1999 first circumnavigated the globe non-stop by balloon, has taught himself and Borschberg techniques of self-hypnosis and meditation in order to maintain concentration.

“Time is not so important anymore,” said Borschberg. “You have plenty of time and the only way to cope with this duration is to be in the present moment. If you start thinking about how many hours left until you get to the destination you get crazy. So the only way is to be present ... In some ways it’s almost a spiritual experience that we are going through.”

For the pilots, the entire journey will resemble circumnavigating the Earth in a family car. The aircraft weighs the same as a Volvo sedan and goes at comparable speeds. SI2’s top speed is 87m/h (140km/h) but the pilots will conserve battery power by limiting the plane to roughly half that.

The cockpit is only slightly larger than an average car and must contain the life support systems, food, oxygen supplies and the reclining pilot’s seat that triples as bed, chair and toilet.

The plane will fly both day and night, carrying no fuel, powered by 17,000 solar panels set on its wings (which are wider than a Boeing 747’s) and fuselage. A 633kg bank of lithium batteries, around a quarter of the entire weight, will store the energy to run the motors overnight.

The stop-start journey harks back to the early days of intercontinental flight before enormous speeds and ranges were made achievable by jet engines. Qantas used to fly the Kangaroo Route from Sydney to London, hopping through Darwin, Singapore, Kolkata, Karachi, Cairo, and Tripoli en route.

Borschberg said the success of the Solar Impulse project, which has already become the first solar-powered plane to fly through the night and the first to fly between two continents, must be seen as a primitive step toward a zero-carbon jumbo.

Combustion of fossil fuels has dominated powered flight since the 19th century dirigible.

Today, aviation burns the most carbon per passenger per kilometre of any mode of mass-transport and, despite efforts to limit emissions, remains the fastest growing anthropogenic source of greenhouse gases. The sector is identified by the UK’s committee on climate change as the toughest major emissions source to decarbonise.

Solar flight seeks to change this but remains decades away at a minimum, says Borschberg.

“We have to realise that we are between the Wright Brothers and Charles Lindbergh periods in the 20s of last century. So it will take, as it took in the past 25, 30, 35 years to fly clean. New technologies will have to be developed, this will take time.”

The deputy editor of Aerospace magazine, Bill Read, said that solar flight was “not yet even remotely ready for any applications in commercial flights”.



“Currently, an aircraft entirely covered in solar cells would not be able to generate enough power to enable it to fly. The Solar Impulse is only able to fly using solar power because it is specially constructed to be very light weight and with a huge wingspan. Unless there is a quantum leap forward in solar cell technology, solar cells cannot yet be considered as a sole power source for aircraft,” said Read.

But Borschberg said some of the advances made for the project have real-world uses today.

“To fly with the sun, day and night, we had to build an aircraft that is extremely energy efficient. These technologies that provide energy efficiency can be used in your home, in your car, in the appliances that you buy,” he said.



The four motors that power the aircraft generate about half the power of a motorcross bike. But unlike conventional engines they lose only 3% of their energy through heat. The standard loss, says Borschberg, an engineer, is around 70%. According to the International Energy Agency, energy efficiency is the single cheapest way to reduce carbon emissions across the world.

“With these technologies we can cope with a major part of the challenge we are facing today in terms of energy, environment, pollution, natural resources and so on,” says Borschberg.