When the Solar Impulse 2 successfully completed its inaugural flight, creators Bertrand Piccard and André Borschberg decided to take this venture a huge step further. They didn’t stop working hard before they achieved their dream in 2016 and saw their solar-powered aircraft fly around the world with no additional fuel. Nice and easy as it sounds, though, making this happen was a long, arduous journey.

The Man Behind the Project

To fully appreciate this achievement, it’s worth understanding a little more about the men behind the plane. Bertrand Piccard is a doctor and a psychiatrist, as well as an astronaut. His ambition to travel round the world isn’t new - he’s known as the first man who flew around the globe in a hot air balloon. Piccard was the co-pilot and chairman of Solar Impulse.

André Borschberg studied Management Science at Sloan School (MIT) and was an engineer at the Swiss Federal Institute of Technology (EPFL). He can fly both airplanes and helicopters professionally and was the co-founder, pilot, and CEO of Solar Impulse. Together, the pair endeavored to do what no man had done before, and circled the globe in a solar-powered aircraft.

Solar Impulse 2
The Solar Impulse 2 is covered with 17,000 solar cells to absorb energy from the sun. Picture Source.

From the Concept to the Final Product

Building a plane capable of flying purely on solar power was no mean feat. It wasn’t the first aircraft to travel by such means, yet it was the first with such a bold ambition. Storing up sufficient solar energy to go around the world was perhaps the major challenge.

It took 12 long years from the concept to making it a reality. 50 engineers and technicians alongside 80 technological partners used their expertise to build the first model of the Solar Impulse aircraft, Solar Impulse 1 (HB-SIA). Along the design process, over 100 suppliers and advisers contributed to create first the prototype and then the final product. After another 5 years and hundreds of specialists involved, the Solar Impulse 2 (HB-SIB) was ultimately ready to set off for its round-the-world flight.

This no-fuel aircraft is truly an impressive specimen. The wingspan stretches 236ft and is covered in more than 17,000 solar cells to absorb energy from the sun. The energy captured on the solar panels is siphoned into lithium polymer batteries which are pre-mounted into four engine nacelles. The engines have broken efficiency records boasting a rate of 94%, and help the aircraft to reach speeds ranging from 36 km/h up to 140 km/h. Powering the entire thing, solar panels take up around 25% of the aircraft’s total weight.

Solar Impulse 2
The Solar Impulse 2 flying at sunset. Picture Source.

As you would expect with two passionate and knowledgeable minds behind the project, every aspect has been accounted for, leading to a slimline aircraft packing only essential weight. The weight of 2.3 tonnes in total means that the jet is around 90% lighter than the finest gliders around. Despite this, the minimalist structure is surprisingly vigorous; honeycomb structures and carbon fiber materials create a balance of rigidity with the lightweight required for aerodynamic travel.

As Piccard said, Solar Impulse 2 showed “the incredible potential of the clean technologies – all these technologies that the world can also use in order to reduce the dependency on fossil fuel and to be cleaner and solve a lot of solve a lot of problems of pollution.” And Piccard and Borschberg certainly took this consideration into account when designing the revered aircraft.

The Big Success

Encouraged by the success from 2014, Piccard and Borschberg continued their efforts towards making the Solar Impulse 2 fly around the world. 

The pilots decided that they’d make stops in every continent to take turns piloting. As Piccard said: “One of us will make the Pacific, one will make the Atlantic; one will cross China the other one will cross America and so on.” And so they did, starting from Al Bateen Executive Airport in Abu Dhabi on 9 March 2015. First, the Solar Impulse went to Oman and India, then to China and Japan. It reached Hawaii in June 2015 and made a few more legs around the US to reach Spain in June 2016. One month later, after a short stop in Cairo, Solar Impulse completed its circumnavigation tour in Abu Dhabi.

The total flight time was over 23 days and nights. During the majority of time Solar Impulse 2 spent in the air it had the ground speed of between 50 and 100 kilometres per hour (31 and 62 mph). Typically, it didn’t move faster to save power. During longer flights such as ocean crossings which took even around five days and nights, the pilots set the autopilot mode on and took 20-minute naps. At each destination, the crew waited for the right weather conditions before setting off for the next leg.

The successful completion of Piccard and Borschberg’s mission showed that the idea of renewable energy replacing finite fossil fuels is a real one. This was a hugely progressive step for the aviation sector as a whole and there is little doubt that, as the Solar Impulse 2 proved it, solar technology will become a very serious consideration in the flying world.