Tomorrow, Swiss aviators Bertrand Piccard and André Borschberg will embark on an epic journey aboard Solar Impulse 2 – an airplane entirely powered by solar power – that will take them around the world. The five-months, 35,000 kilometers long trip will start and end in Dubai.

Solar Impulse 2, a solar-powered airplane. Image: Solar Impulse

Wait a minute – five months?! We need to talk a bit about the plane itself, first. With a wingspan larger than a Boeing 747’s, Solar Impulse is completely covered in solar cells. Almost 17,000 to be more precise. These power electrical motors which in turn spin rotors and also charge four giant lithium batteries which weigh a monstrous 633 kg. This way, the plane can theoretically fly non-stop, even through cloudy or dark weather. Because it has a low cruising speed (140 km/h) and, most importantly, the flight conditions aren’t exactly mint (temperatures inside range from -40 to 40 degrees Centigrade, the cockpit is extremely crammed, and there’s no room to sleep), the two pilots are forced to make their journey in 12 legs, each one spanning 25 days.

The first version, Solar Impulse I, made worldwide headlines after it was the first 100 percent solar-powered aircraft that flew for 26 hours straight. It is also the first solar powered aircraft to cross two continents.

The Solar Impulse 2, a solar-powered plane, flies over the Sheikh Zayed Grand Mosque in Abu Dhabi during preparations for next month’s round-the-world flight on Feb. 26, 2015

Like solar powered cars, the aim of the project isn’t to replace conventional aircraft. Flying for 25 days in a kitchen on wings isn’t exactly comfortable, by modern standards. Of course, as solar power advances, solar powered vehicles or aircraft might become feasible, but for now solar energy works for land-based, static power generation only. So what’s their angle? Why, it’s a publicity stunt of course. One that I think we can all agree is for a great cause – to help raise awareness and show people how versatile solar energy can be. I, for one, salute the whole idea. It takes a lot of guts to do it, I forgot to mention.

To pilot the aircraft for up to five days straight, each of the two pilots  can’t sleep longer than 20 minutes every two to four hours. To cope, the pilots have been practicing  yoga and self-hypnosis.

“I had this dream 16 years ago of flying around the world without fuel, just on solar power,” said Piccard. “Now we’re about to do it.”

Follow Solar Impulse in the live stream below.