In a record breaking flight this week a solar powered plane successfully completed the highest and longest ever flight by a solar aircraft.  The huge wings of the plane, known as the Solar Impulse, and its horizontal stabilizer contain 12,000 silicon mono-crystalline solar cells. Energy from the sun is stored in lithium batteries and used to  provide the aircraft's 4 electric engines with the power they need to fly the plane. The Solar Impulse flew throughout the whole night for the first time during the evening of 7th July and morning of 8th July 2010.

The Solar Impulse project started in 2003.  During the last year, things have moved rapidly.  The plane was unveiled on 26th June 2009 and took its first tentative taxi down the runway under its own solar power on 19th November 2009.  A few weeks later at 1.11pm on 3 December 2009 at Dübendorf Airfield in Switzerland, the plane was taken up to its take-off speed of 35 kilometers per hour for its first "flea hop" - flying around 350 metres of distance at a one meter altitude.

Solar Impulse's First Flea Hop

 

The first full flight came on 7 April 2009 when the Solar Impulse completed an 87 minute flight, climbing to slightly under 4,00 feet  

The Plane's First Flight

The whirring sound is a helicopter accompanying the plane.  The Solar Impulse itself is virtually silent, as can be seen in the video below. 

This week it took to the wing for its greatest challenge so far.  At 6.51 on the morning of 7th July at Payerne airbase in Switzerland, using its 4 propellors to lift itself into the sky by the power of the sun, the Solar Impulse began its 26 hour flight. 

Take Off for the plane's first ever Solar Powered Night Flight

Flying through the skies above Switzerland, the Solar Impulse reached a height of 28,000 feet and a speed of 78 miles an hour.

The cockpit was not presurised, so the pilot, CEO and co-founder Andre Borschberg, had to rely on an oxygen mask and cope with temperatures of minus 28 degrees celsius at an altitude of 8,000 metres.  He had a supply of energy bars, rice pudding, sandwiches and coffee to keep him going, but nowhere to...well...go...so had to use plastic bags to relieve himself.   After a few hours he said he was feeling great though.

Andre had to remainfully alert throughout the 26 hour and 9 minute flight, as the plane did not have an autopilot system to back him up.  The enormous 63.4 meter wingspan, being a similar size to the span of an A340 Airbus, combined with its light weight, meant that the plane required very careful piloting.

From its maximum altitude the plane started a slow descent, which brought it down to 1,500 meters at around 11.00PM. From that time the energy that the batteries had stored during the day had to keep the plane flying until the next morning's sunlight.

Andre was monitored by ground staff throughout the night to ensure that he didn't fall asleep as the plane flew in the darkness.  In addition, he wore a special jacket whose sleeves were programmed to vibrate in the event of the aircraft tipping beyond a 5 degree tilt.  

The plane finally landed successfully and smoothly at 9.00AM on 8th July 2010.  On leaving the cockpit, Andre Borschberg emotionally described the flight as the most incredible of his 40 year flying career, and described the thrill of watching the battery charge level continually rise during the day thanks to the sun's energy, then the suspense of not knowing whether the plane would stay up during the entire night, and finally the joy of seeing the sunrise and feeling energy starting to circulate in the solar panels once more. "Sitting in a plane producing more energy than it consumes is a fantastic feeling”, he said, adding “I have just flown more than 26 hours without using a drop of fuel and without causing any pollution!”

It is hoped that the experiment will be the beginning of new environmentally friendly methods of air travel. something which would be of great value when it comes to saving the planet, as currently aircraft emit a significant amout of carbon dioxide and a number of other very harmful pollutants.  In 1999 for example, the Intergovernmental Panel on Climate Change estimated that the carbon dioxide emissions of aircraft contribute about 2 percent of the overall effect toward global warming and climate change.  In 2007, the British Airline Pilots' Association (BAPA, an organisation in favour of air travel) confirmed that air travel accounts for two to three percent of global carbon dioxide emissions.  BAPA predict that this will rise to 6 percent by the year 2050.

The Solar Impulse plane has been described as a new chapter in aviation history and a breakthrough for renewable power.  It was indeed  an extraordinary flight powered entirely by energy from the sun.

The aircraft stretches current technology to the limit.  Its components are featherweight and the small cockpit is only large enough for one person.

Naysayers say that this shows that the new technology still has a long way to go.  The plane has only the same power as a motor scooter.

However, supporter say it offers a vision of a future world powered by our star, the sun.  Its inventors believe that the combination of renewable technology and lightweight materials has the potential to eventually revolutionise air transport.

Andre Borschberg, the pilot, said "this solution is not sufficient of course to transport many people but we have to remember that when Lindberg did his crossing over the ocean in 1927 he was also alone and we needed further technological development to transport a hundred people.  That's the same situation here."

This is intended to be just the start. An attempt at a trans-Atlantic crossing is intended in 2012.  Once this has been achieved, the inventors hope that by 2013 solar cells and batteries will have improved enough to fly the plane on an around the world flight.