How does this plane circle the globe without refuelling?

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We’ve all heard of planes without pilots. But planes without petrol?

If it sounds like an environmentalist’s dream, that’s probably because that’s just how it started.  But this year, that dream might start setting records.

Two Swiss pilots are set to make aviation (and energy) history by flying around the world without using a single drop of fuel.

Perpetual travel needs precise technology

Even the best commercial aircraft can’t go for much longer than twelve hours without a fuel stop.  So you can imagine just how much work went into the engineering of a craft that can fly forever.

The Solar Impulse-2 has more than 17,000 solar cells on its back, wings and tail, covering an area of almost 270 square metres and generating up to 340kWh per day.

It’s also incredibly light for its size: its engineers have shaved off every spare gram imaginable.

With a wingspan of 72 metres, it’s wider than a Boeing 747 – but at only 2.3 tonnes, it weighs just about as much as a small van. The solar-powered plane’s structure is so light, in fact, that its batteries alone account for around a quarter of its entire weight.

Unfortunately, it’s stuck with the speed of a small van, too: with a top speed of just 140kmph, Solar Impulse-2 won’t be setting any speed records.

The limiting human factor

Of course, a perpetual plane can only go so far before the pilot nods off.  That’s why it will take two pilots in alternating shifts to take the one-seater plane through its entire global journey.  But it still won’t be easy.

To get across the huge expanses of the Pacific and Atlantic oceans with an average speed of just 70 kmph, they may have to fly for five consecutive days at a time.  They’ll be snatching 20-minute power naps and going to the toilet in their specially designed pilot’s seat – all while hooked up to oxygen tanks in a tiny, unpressurised cockpit.

‘What is really special, is that it is the first and only airplane in the world which has unlimited endurance,’ says pilot André Borschberg.  ‘We have an airplane which is fully sustainable in terms of energy, and our challenge now is to make the pilot sustainable as well.’

The mission is more than just the journey

Despite five long months and a 35,000km journey ahead of them, Solar Impulse’s mission is about more than just setting records and racking up air miles.

By completing a circuit of the entire planet using only renewable energy, they hope to ‘demonstrate the importance of clean technologies for sustainable development; and to place dreams and emotions back at the heart of scientific adventure’.

This journey is likely to represent a milestone in the raising of public awareness to the potential of renewables.

If they can power a plane night and day across the entire world, just think how much clean energy we could get by using solar panels for our businesses and homes.

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