Soaring the globe on solar power

ABU DHABI, United Arab Emirates — With its wings stretched wide to catch the sun’s energy, a Swiss-made solar-powered aircraft took off from Abu Dhabi just after daybreak Monday in a historic first attempt to fly around the world without a drop of fossil fuel.

Solar Impulse founder Andre Borschberg was at the controls of the single-seat aircraft when it lumbered into the air at the Al Bateen Executive Airport. Borschberg will trade off piloting with Solar Impulse co-founder Bertrand Piccard during layovers on a 35,000-kilometre journey.

Some legs of the trip, such as over the Pacific and Atlantic oceans, will mean five days and five nights of flying solo. Both pilots have been training hard for this journey, which will span 25 flight days over five months before this Spruce Goose of renewable energy returns to Abu Dhabi in late July or August.

The Solar Impulse 2 aircraft, a larger version of a single-seat prototype that first flew five years ago, has a wingspan of 72 metres, larger than that of the Boeing 747. Built into the wings are 17,248 ultraefficient solar cells that transfer solar energy to four electrical motors that power the plane’s propellers. The solar cells also recharge four lithium polymer batteries.

Although the aircraft’s average flight speed will be 70 km/h, Piccard says the optimal speed for the lightweight Si2 — made of carbon fibre — is about 25 knots, or 45 km/h.

Borschberg has been practising yoga and Piccard selfhypnosis in order to calm their minds and manage fatigue. They aim to rest a maximum of 20 minutes, repeating the naps 12 times over a 24-hour period. Goggles worn over the pilot’s eyes will flash lights to wake him up.

Armbands will buzz if the plane isn’t flying level.

The plane will reach an altitude of about 28,000 feet during the day to catch the sun’s rays and at night dip to about 5,000 feet when flying over the ocean.

After two stops in India, the Si2 will head to China, where it will stay for a month until the days are longer to catch more of the sun’s energy. It will also make stops in Myanmar, Hawaii, Phoenix and New York. The path across the Atlantic will depend on the weather and may include stops in southern Europe or Morocco.