Solar Impulse has taken off from Hawaii after an eight-month hiatus enforced by battery damage to continue the trans-Pacific part of its round-the-world trip powered solely by the energy from the Sun.
Bertrand Piccard is at the controls of the single-seater plane heading for California, which he is expected to reach on Sunday.
The team said the plane has performed well during the first hours, with its batteries nearly fully charged before dark to continue flying during the night. The plane has already reached a point beyond which it is impossible to return to Hawaii if anything goes wrong.
The attempt to circumnavigate the world in a fully solar-powered plane was suspended last year in early July after the first and longer part of the trans-Pacific crossing. The five-day flight from Japan to Hawaii broke several records including that for the longest solar-powered flight by time and distance, as well as that for the longest solo flight. André Borschberg was piloting the craft during the record-breaking crossing, after which the plane had to be grounded due to battery damage caused by overheating. The team later said the batteries were wrapped in too much insulation. The rest of the round-the-world trip had to be postponed due to the approaching season of bad weather.
Piccard’s take-off was slightly delayed due uncertainty about winds. The two trans-Pacific legs are the riskiest part of the plane's global travels due to the lack of emergency landing sites.
Piccard said the idea of crossing the ocean in a solar-powered plane a few years ago stressed him out, but on Thursday he was confident things would go according to plan.
The support team is now separately travelling to Mountain View, California, ahead of Solar Impulse’s arrival.
Solar Impulse’s pioneering journey started in March 2015 in Abu Dhabi. The team had to put up with several delays from the start caused mainly by bad weather. The first attempt to cross the Pacific Ocean had to be aborted due to strong winds, which forced the plane to make an unscheduled stop in Japan’s Nagoya.
The carbon-fibre plane, only about the size of a personal car, has a wingspan of a Boeing 747, with the wings’ surface covered with 17,000 solar cells. The solar cells power the aircraft during the day and charge its batteries so it can continue flying at night. It cruises at a modest speed of around 50km/h.