Solar-power plane to conquer the Earth

An interesting article by Ryan Whitwam writing for Extreme Tech on March 5:

A team of Swiss engineers, aviation experts, and designers is finishing final preparations to launch Solar Impulse 2, a solar-powered plane with a wingspan larger than a Boeing 747. When Solar Impulse 2 gets airborne next week, it will begin a historic trip around the world. If all goes to plan, this will be the first aircraft to circumnavigate the globe powered entirely by the sun.

The Solar Impulse 2 has a huge wingspan, but the carbon fiber body of the plane is quite narrow. There’s only space for a single person (the pilot), and it doesn’t sound particularly comfortable. The design dedicates only 3.8 cubic meters of space for the pilot, which is just enough for the reclining multipurpose seat. It’s a chair, bed, and even a toilet. The cabin is also unheated and unpressurized, so the pilot will need to rely on oxygen canisters and thermal insulation in the cockpit structure.

Solar Impulse 2 will be piloted by the organization’s co-founders Bertrand Piccard and André Borschberg. They’ll take turns being crammed into this unpleasant little space for several days at a time, including one five day stretch over the Pacific Ocean. The round-the-world trip is being made in 12 legs over the course of several months, so the pilots will have the chance to trade places after each layover. This also gives the Solar Impulse team a chance to make sure the plane is still in proper working order. Even with years of testing, there’s a lot that can go wrong.

Solar Impulse 2 has 17,248 solar panels covering the wings, which can soak in enough power during the day to keep the four propellers going all night. Power will be stored in the craft’s lithium-ion batteries for use at that time as well. The batteries take up about a quarter of Solar Impulse 2’s 5,000-pound heft. That’s about the same as a midsize sedan, which is light for a plane and good for overall efficiency. Solar Impulse 2 can reach speeds of nearly 100 mph, but the plan is to limit speed to about 60 mph to get a little more distance out of the batteries.

The team arrived in Abu Dhabi, United Arab Emirates two months ago to conduct the final tests of Solar Impulse 2 before beginning the real flight. The plane has been taken on several multi-hour test flights in Abu Dhabi, and the pilots report no issues. The test flights were less than 250 miles, though. Several of the legs will be a few thousand miles, but Piccard and Borschberg are confident the plane will perform well.

Takeoff is currently scheduled for Monday March 9th. That first leg will be a short one, just a few hundred miles to Oman. Future legs will be longer with stops in Nanjing, Hawaii, New York, North Africa, and more. It would be more impressive if the plane managed the trip in one go, but this is still a huge technical achievement. Future solar aircraft might not need checkups every few thousand miles, but humans will still like to get out and stretch their legs.

Good luck to them!