Solar Impulse 2 was unveiled today in Payerne, Switzerland (Credit: Solar Impulse)

Round-the-world solar plane unveiled

A solar-powered airplane designed to make the first flight around the world without any fuel has been unveiled in Switzerland.

Solar Impulse 2 is the brainchild of psychiatrist and explorer Bertrand Piccard and engineer and entrepreneur André Borschberg, who last year flew their prototype plane Solar Impulse across the USA.

The single-seater solar aircraft’s wings are 8m metres bigger than the prototype at 72m – roughly the width of a Boeing 747 – and are coated in solar panels that power the aircraft and charge an array of on-board batteries that allow it to fly through the night.

The aircraft’s sedate cruising speed of between 36 km/h and 140km/h depending on altitude and wind means it will have to fly for up to 5 consecutive days and nights over oceans from one continent to another to complete the round-the-world flight, due to take place next year.

“When Solar Impulse was born 12 years ago and could show the enormous wings on computer design all the specialists in the world of aviation started to laugh,” said Picard, speaking at the unveiling ceremony in Payerne.

“Today this airplane exists. It’s the most incredible airplane of its time. It can fly with no fuel day and night and we hope that we can make it around the world.”

According to Borschberg, the team have had to work extensively on reliability due to the long journey times and improved performance so they know that if they hit adverse weather a few days into a flight the plane can still fly with partial cloud cover.

“When we started this project a little bit more than 10 years ago the first idea Betrand had was to contact the aircraft manufacturers because these companies would know how to be light weight,” he said.

“We proposed to them that we wanted to build this airplane and very quickly they came back and said it’s not possible. But as we were sure there was a solution we decided to set up our own team and begin to look for our own solution.”

The Solar Impulse 2 cockpit The plane is constructed from a lightweight carbon composite that weigh just 25g per square metre giving the plane a weight of only 2,300kg and the planes four electric motors have an efficiency of 94 per cent.

The plane features a 3.8m3 cockpit designed to allow the pilot to live there for a week but for the sake of energy efficiency the cabin is not pressurized or heated. As the plane flies at an altitude of 8,000m where the lack of oxygen is fatal the pilot has to wear an oxygen mask while cruising.

“What is really unique about these two airplanes is they are the only airplanes in the world that have unlimited endurance,” said Borschberg. “These two airplanes are the most energy efficient ever designed. We had to drastically reduce the energy consumption of these airplanes to make it feasible to fly through the night.”

Flying for days at a time will require the pilot to sleep, so the plane will also feature a virtual co-pilot system designed by engineering firm Altran that can control the plane while the pilot is indisposed. The system also includes a software program that monitors data from both the virtual co-pilot and the planes sensors to alert the pilot if there is a problem via a vibrating device worn on the wrist.

Test flights are due to take place in May, followed by training flights over Switzerland, and the circumnavigation attempt is scheduled to start in March 2015 from the Gulf area.

Piloted by the two founders, the plane will fly over the Arabian Sea, India, Burma, China, the Pacific Ocean, the USA, the Atlantic Ocean and Southern Europe or North Africa before returning to the departure point. Landings will be made every few days to switch pilots and organize public events for governments, schools and universities.

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