A solar-powered plane

A solar-powered plane able to fly in sunshine or darkness without using any fuel took off yesterday (June 29) on a planned 120-hour flight across the Pacific Ocean, from Nagoya, Japan, to Kalaeloa and Hawaii.

The Solar Impulse 2  took off from Nagoya runway at 3:03 a.m. local time in Japan (2:03 p.m. EDT on June 28). The flight, which is anticipated to take five days and five nights, is part of an successful attempt to travel the world using only solar power.

The travel-the-world attempt began March 9 in Abu Dhabi, in the United Arab Emirates. On May 31, Solar Impulse 2 tried to complete the seventh leg of its journey, from Nanjing, China, to Kalaeloa, but the flight was diverted to Nagoya due to bad weather. Last week, after spending few weeks in Japan, the plane was again grounded due to poor weather conditions. But today's attempt went off without a problem and delay.

"Now in the flight to Hawaii. Very strong emotions as I cleared the point of no return: exploration starts from here," pilot Andre Borschberg, who is also the CEO and co-founder of Solar Impulse, wrote in an update on Twitter. Borschberg included a photo of the Solar Impulse 2 soaring over a bed of fuzzy clouds.

Bertrand Piccard, the chairman and founder of Solar Impulse and its other pilot, will help Borschberg from the Mission Control Centre in Monaco. Borschberg and Piccard both have been alternating being at the controls of the single-seater plane.

Staying alert for such a long alone flight poses many difficult task , but Borschberg plans to take just 20-minute naps(small sleep) and meditate to keep his blood moving appropriately and his muscles relaxed. Piccard  told us before that he uses self-hypnosis to keep concentrated during long flights. Piccard is expected to pilot the solar plane on the another leg of its journey, from Hawaii to Arizona.

The Solar Impulse 2 is charged by 17,000 photovoltaic cells on its air-wings, which drive properly during the day and charge batteries that power the airplane at night. There will be 13 flights in total, if all continues according to the plan, according to Solar Impulse officials