Earlier this month, we brought you the story of Solar Impulse 2, the world's first fuel-free, solar-powered aeroplane. From its initial take-off in Abu Dhabi, Solar Impulse has successfully completed flight legs to Muscat, Ahmedabad, Varanasi and Mandalay, prior to its most recent landing in Chongqing, where poor weather conditions have temporarily halted its progress.
Solar Impulse 2 will delay the next leg of its journey until a meteorological window of opportunity presents itself over eastern China, allowing a safe flight to Nanjing. The team behind the project will use the extended stopover time to further promote its "future is clean" campaign, highlighting the critical role that renewable energy will play in the future.
With Swiss pilot Bertrand Piccard at the controls, the plane encountered unforgiving conditions on its 20-hour flight from Mandalay, before facing the challenges of high winds and other air traffic upon descent into the busy hub of Chongqing International Airport. After touching down at 17.35 UTC, Piccard declared that managing to land in such difficult conditions was extremely reassuring, in view of the numerous further challenges that the pilots will face in subsequent legs of the Round-the-World tour.
The environment encountered at 35,000 feet means that life on board Solar Impulse 2 is harsh, with each pilot spending as long as five days in the cockpit at a time. To save weight, the plane does not offer any of the home comforts we expect to find on board a commercial aircraft, such as a toilet, heating and enough room to move around. The pilots must recline the seat in the tiny cockpit to exercise, and use a hole below the seat as a toilet. Whilst brushing teeth is allowed, a razor was deemed 'extra weight' - ensuring continuity for the traditional adventurer's beard. Putting budget airlines around the world to shame, Solar Impulse 2 provides its pilots with nutritious foods like quinoa, spelt and tabouleh, incorporated into bespoke dietary plans.
Due to the lack of a full autopilot, the controls can only be left alone when the plane is in stable flight and the weather is clement, as the lightweight plane is highly susceptible to buffeting when subjected to wind. Naps are confined to 20 minutes, after which flashing goggles and a vibrating seat will awaken the pilot. Despite the inhospitable conditions, the team behind Solar Impulse 2 recognises the importance of completing the mission. Multiple robust safety systems ensure the wellbeing of the pilot in the event of a serious issue, and a successful circumnavigation will prove the viability of solar as a sustainable method of transport.
Solar Impulse 2's 72m wingspan is home to 17,000 135μm-thick photovoltaic cells, which store power in four batteries and power four electric motors. The plane is able to stay airborne through a combination of enormous lift, provided by the wings, low drag, from the plane's aerodynamic construction, and lack of weight, reducing the effect of gravity.
After the next leg of Solar Impulse 2's journey comes one of the most difficult and dangerous stages of the mission - a trans-pacific flight. For now, pilots Piccard and André Borschberg can relax and enjoy a less strenuous stage of their itinerary. We'll be ready to update you when the pair resume their world record attempt.