The sky's the limit

After eighteen hours and 898km of strong headwinds, turbulence and even some backwards flying, Bertrand Piccard's plane landed successfully in Madrid without the aid of a single drop of fuel.

On Friday 6^th July, the aptly-named Solar Impulse completed the returning leg of its first intercontinental flight, powered only by the sun and with a 90-strong team of engineers, technicians and mission controllers behind it. But this huge achievement was not without its difficulties.

As well as the unpredictable meteorological conditions which caused the flight to be postponed by three days, Piccard and his team were dragged back down to earth with many technical problems.  Jacques van Rijckevorsel, responsible for chemical group Solvay's involvement in the project, likened the plane to a "flying laboratory" last year and admitted the $100m project had been "extremely demanding". Indeed, without the help of their partners including Solvay and materials provider Bayer Material Science, Solar Impulse's triumph would not have been possible. Bayer Material Science's researchers contributed ideas on both lightweight construction and energy efficiency, while Solvay conducted computer-based simulation to predict the behaviour of these lightweight materials during flight.

The project commenced in 2003, when Swiss duo Piccard and André Borschberg envisioned a plane powered entirely by the sun. 11,628 monocrystalline silicon cells, a hundred partners, nine years and two prototypes later, their dreams have come true. The commercial-airline-sized prototype first took off in 2010, and since then has also flown up to twelve hours and through the night. But last week's intercontinental success was the first of its kind and will remain a milestone for the Solar Impulse project.

Despite their previous successes, the sky remains the limit for Piccard and Borschberg. In 2013 Solar Impulse will attempt to break the round-the-world record in five legs of five days. And for these aviation pioneers, as well as saving energy and demonstrating solar power's potential, they view their accomplishment as "a symbol that affects all of us". As the project's website states, solar aeroplanes are unlikely to ever carry 300 passengers. But Solar Impulse's triumph shows us that a sustainable future for air travel may be on the horizon.

By Becky Wilson