Solar Impulse : Inventing the Future

HB-SIA, Solar Impulse’s prototype experimental aircraft is first and foremost a symbol. The project was launched as a means to create positive emotions around clean technologies. Promoter of sustainable development and energy savings, the solar aircraft is also a technological breakthrough for renewable energies. It is not however the world’s first solar aircraft as there have been several others before it, drones and manned ones. What distinguishes HB-SIA is its ability to fly day and night only powered by solar energy, bringing the notion of perpetual and fuel-less flight closer to reality.

Originally built only to prove the potential of solar energy to fuel for a day and night flight, HB-SIA has exceeded expectations. After completing a 26-hour flight in 2010, and gaining three FAI world records, the Solar Impulse airplane went on to do some sightseeing in Switzerland flying to Geneva and Zurich. In 2011, the prototype completed its first international flight leading it to Brussels and to the Paris-Le Bourget Air Show, but the greatest milestone yet occurred during the summer of 2012.

Upon invitation by His Highness King Mohammad VI, HB-SIA made its way to Ouarzazate, doorstep of the Moroccan desert, via Madrid and Rabat and return via Madrid and Toulouse concluding the world’s first solar-powered intercontinental flight in 6’000km and seven legs. The adventure earned it two additional FAI world records and further proved the viability of its technology.

What makes Solar Impulse’s aircraft so unique is its size (wingspan 63.40m), its lightweight (1600kg), and 100% powered by the sun. But for air traffic controllers there’s even more to it: an aircraft that flies at the speed of a scooter in a sky crowded with Formula 1’s: it’s a real challenge to trace its route and to ensure, at the same time, that normal air traffic flows undisturbed.

How does this big bird really fly? Equipped with four motors and four lithium batteries, every flight is composed of cycles revolving around energy savings and optimization.  During the day, the pilot ascends to a higher altitude in thinner atmosphere to avoid turbulence and cloud formations. The higher HB-SIA climbs, the more sun power is available and can be stored in the batteries. As the sun begins to set, the pilot reduces the motors and initiates a gentle descent to a low night loitering altitude of 1000-1500m meters. Out of its maximum altitude of 8000m, the prototype can glide for 4-5 hours consuming almost no energy. When the lowest altitude is reached in the middle of the night, the motors, now powered by the batteries, are used to maintain a cruising speed of 25 knots until the morning. As the breathtaking tones of sunrise start filling the sky with warmth, the aircraft can once again begin its ascent, and the cycle begins.

HB-SIA - Solar Impulse during flight over Switzerland 2012

Crossing frontiers – Flight to Morocco – Landing in Rabat-Salé - André Borschberg and Bertrand Piccard after the landing, 2012.06.05

The next mission: After a delay in the building of the second aircraft HB-SIB, to be used for Global flights, it was decided to disassemble the HB-SIA; ship to the USA and re-assemble to fly a new mission 'Crossing of America'.

You can view the latest video from this next mission ACROSS AMERICA: DISASSEMBLY AND SHIPMENT