Solar Impulse 2, which landed in Abu Dhabi on Tuesday, completing a circumnavigation of the globe, is a study in contrast. It has the wingspan of a 747 but weighs the same as a car. It has flown 40,000 km around the world, but at an average speed of 70 kmph, again like a city car. And it has set a most unusual world record, getting all this done without using any fossil fuels at all, relying on 17,000 solar cells.
Bertrand Piccard, the Swiss psychiatrist, balloonist and pilot who was at the controls on the last leg of the flight from Cairo to Abu Dhabi, touched down after logging 48 hours and 37 minutes in the air — maybe 10 times longer than a commercial flight would have taken. Landings are so slow that cyclists pedal along underneath, grab hold of undercarriage struts and help the plane down. But speed was never the point of Solar Impulse. It was a promotional project to demonstrate the viability of solar power, by putting it to the most challenging use — heavier than air flight, including night flying. It faced difficulties only on the longest leg of the journey, the trans-Pacific flight from Japan to Hawaii, when its batteries were damaged by heat.
More than 9,000 dramatic images and videos of the flight — over the Cheops pyramid and the Atomium in Brussels, for instance — have drawn quite as many fans as Nasa’s feeds from probes and the International Space Station. Like a magnifying glass used to focus the sun’s rays, Solar Impulse 2 has ignited the imagination, telling us that clean energy is already possible, though the climate wars rage on. Who knows, perhaps the next credible target will be the dream of 20th century science fiction, to send sailcraft powered by the solar wind to the outer planets.