Solar jet on a record-breaking tour
Explorers André Borschberg and Bertrand Picard have been flying around the world with a plane called Solar Impulse inspiring people that green aviation is the future.
We have always used the energy of the Sun as far back as humans have existed on this planet. Ancient civilizations learned how to build their homes so they could save up the Sun's energy during the day to keep their homes warm at night, and in the 20th century solar solutions began to become more commonplace at home in the form of solar cookers, heating and lighting systems.
Now the technology is moving into the realm of flight. Weighing about the same as a family saloon car, Solar Impulse 2 is a Sun-powered single-seater aircraft with a wingspan slightly less than that of an Airbus A380, the world's largest passenger jet. It features a non-pressurized cockpit, an autopilot to allow for trans-oceanic flights and supplemental oxygen, which allows the pilot to cruise at high altitude.
Critically, there's no fuel tank. Instead its wings are covered by more than 17,000 photovoltaic (solar electricity-producing) cells. These supply 4 electric motors that drive propellers to keep the plane aloft. Surplus current from the cells also charges a bank of lithium-ion batteries, which store energy for night flights.
Solar Impulse 2 switches between two operating altitudes. Ascending to 28,000 feet, it soaks up sunlight and charges the batteries before descending to a lower, more efficient "operating" altitude of 5,000 feet. This is how the plane remains aloft at night.
Following take off from Abu Dhabi, the capital of the United Arab Emirates, and stopping in Oman, Myanmar, China, Japan and then then US, the plane's original 2015 world tour came to an abrupt halt owing to problems with overheating batteries.
This incident grounded the plane in Hawaii until Spring 2016 when test flights were resumed. The plane then moved rapidly around the Earth and completed a first transatlantic solar and electric crossing in June 2016, landing in Sevilla.
Piccard and his colleague Andre Borschberg, have each been taking turns at the controls during each leg of the journey.
While zero-fuel planes had been around before Solar Impulse 2, no previous solar aircraft had successfully flown at night. And although this single-seater plane has a long way to go before it can challenge a passenger jet, it does carrying a message of sustainability: that the future is clean.
"It's crazy, it's unbelievable! Getting the sun from the space makes it efficient to fly forever," enthuses André Borschberg, the CEO, co-founder, and co-pilot of Solar Impulse.