Solar Impulse Plane Set To End First Leg of Epic Flight

The first leg of a record-breaking attempt to fly around the world in a solar-powered plane is approaching an end.

The aircraft - called Solar Impulse-2 - is preparing to land at Muscat in Oman after a 12-hour flight.

Piloted by Andre Borschberg, it began its epic journey in Abu Dhabi.

Over the next five months, it will skip from continent to continent, crossing both the Pacific and Atlantic oceans in the process.

The single-seater vehicle took off at 07:12 local time (03:12 GMT).

Mr Borschberg will share the pilot duties in due course with fellow Swiss, Bertrand Piccard.

The plan is stop off at various locations around the globe, to rest and to carry out maintenance, and also to spread a campaigning message about clean technologies.

Before taking off, Borschberg told BBC News: "I am confident we have a very special aeroplane, and it will have to be to get us across the big oceans.

"We may have to fly for five days and five nights to do that, and it will be a challenge.

"But we have the next two months, as we fly the legs to China, to train and prepare ourselves."

Monday's leg to Oman will cover about 400km and take an estimated 12 hours. Details of the journey are being relayed on the internet.

 A solar revolution - by Roger Harrabin, BBC environment analyst

It's a deep-breath moment in the history of technology as Solar Impulse soars to the skies.

Because, pinch yourself, solar power is predicted to become the dominant source of electricity globally by 2050.

The price of solar electric panels fell 70% in recent years and costs are expected to halve again this decade.

And Deutsche Bank forecasts that, based on current fossil fuel prices, solar will produce power as cheaply as gas in two thirds of the world before 2020.

In the UK the solar industry thinks it can compete with wind within 18 months and with gas in the near future. In the USA, solar jobs already outnumber coal jobs.

The solar revolution was sparked by government subsidies, which attracted venture capitalists to fund innovation and created a huge market that Chinese manufacturers are battling to exploit.

The solar boom is a huge help in the battle against climate change, but scientists warn it's not nearly enough. And we must find ways of storing that mighty but capricious power, and making it work with the grid.

Lightweight plane

The Solar Impulse project has already set a number of world records for solar-powered flight, including making a high-profile transit of the US in 2013.

But the round-the-world venture is altogether more dramatic and daunting, and has required the construction of an even bigger plane than the prototype, Solar Impulse-1.

This new model has a wingspan of 72m, which is wider than a 747 jumbo jet. And yet, it weighs only 2.3 tonnes.

Its light weight will be critical to its success.

So, too, will the performance of the 17,000 solar cells that line the top of the wings, and the energy-dense lithium-ion batteries it will use to sustain night-time flying.

Operating through darkness will be particularly important when the men have to cross the Pacific and the Atlantic.

The slow speed of their prop-driven plane means these legs will take several days and nights of non-stop flying to complete.

Piccard and Borschberg - whoever is at the controls - will have to stay alert for nearly all of the time they are airborne.

They will be permitted only catnaps of up to 20 mins - in the same way a single-handed, round-the-world yachtsman would catch small periods of sleep.

They will also have to endure the physical discomfort of being confined in a cockpit that measures just 3.8 cubic metres in volume - not a lot bigger than a public telephone box.

  If the pilots should come unstuck over the Pacific or the Atlantic, they will bail out and use ocean survival gear until they can be picked up by a ship.

Of the two protagonists, Andre Borschberg perhaps needs a little more introduction.

A trained engineer and former air-force pilot, he has built a career as an entrepreneur in internet technologies.

Bertrand Piccard, on the other hand, is well known for his ballooning exploits.

Along with Brian Jones, he completed the first non-stop, circumnavigation of the world in 1999, using the Breitling Orbiter 3 balloon. The Piccard name is synonymous with pushing boundaries.

Bertrand's father, Jacques Piccard, was the first to reach the deepest place in the ocean (a feat achieved with Don Walsh in the Trieste bathyscaphe in 1960). And his grandfather, Auguste Piccard, was the first person to take a balloon into the stratosphere, in 1931.