The Solar Impulse has become the first solar-powered aircraft to complete an international flight -- a feat that moves it one step closer towards the eventual goal of making a trip around the world without gas.
On Friday, the aircraft took off from Payerne in western Switzerland and landed 13 hours later at Brussels airport in Belgium. In July, the plane had set the record for the longest solar-powered flight when it flew over Switzerland for a little more than 26 hours before returning to the airfield where it took off.
Although the Solar Impulse didn't stay airborne for nearly as long this time around, the stunt presented some navigational challenges for the flight team. The aircraft is equipped with a 200-ft. wingspan and 12,000 solar cells, which only enables it to fly at an average speed of 31 mph. This meant the crew had to ensure the plane followed a route that didn't interrupt the flow and traffic of commercial flights traveling at speeds that can be almost up to 20 times faster.
Solar Impulse Air Traffic Control manager Niklaus Gerber recounts just how tricky it was to pull off the flight on the Solar Impulse Blog:
"HB-SIA is an obstacle for civil and military aviation because it is not very mobile, and rather inflexible. It is slow (31 mph/50 km/h) and does not really show up on radar (you see it as a point that hardly moves). Now, alongside it, there are aircraft that are traveling at between 400 and 900 km/h. So the other aircraft are the ones that have to make adjustments to avoid it. But this scenario is theoretical because we have done everything to avoid it in planning the flight. Usually, the separation distance between aircraft is 300 meters (984 ft) vertically and 8 kilometers (5 miles) when flying at the same height. In the case of Solar Impulse, our margin of safety is much greater. And an aircraft that passes above it needs to be at least 900 meters (2,953 ft) higher, due to the turbulence it creates which descends for about 5 minutes at a rate of 150 meters (492 ft) per minute before dissipating."
While the Impulse is a long way from servicing passengers and cargo in the same manner as commercial airlines, it has demonstrated what's possible with a renewable energy source like the sun. Now if they could also figure out a way to harness wind energy, that would be something. Wouldn't it?
Here's footage of the flight:
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