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Marco Werman: If you want to find nautical terms today, the best thing to do is look up in the sky and find an airplane. Think about it: captain, galley, measuring speed in knots. Our next story is about a plane, it’s called Solar Impulse 2, and it’s not speedy but that’s not really the point. As the name implies, it’s a completely solar-powered plane and it’s currently trying to make a round-the-world voyage. Swiss pilot Andre Borschberg is en route from Japan to Hawaii as we speak. This is the longest flight the plane has made on its journey around the globe so far.
John Hansman: This particular flight is really on the edge of the envelope. It’s a five-day flight; he’s committed now, he’s past the point of no return, so hopefully everything will work out.
Werman: John Hansman is a professor of aeronautics at MIT. He says Solar Impulse 2 is a unique aircraft.
Hansman: This airplane is entirely solar-powered. It has batteries on board to help make it through the night. But by pushing the envelope, I really meant in terms of the flight. This is a five-day flight--the longest that he’s flown it before is two and a half days. If they hit any bad weather, it’s a real problem. In a cloudy area, it can’t refuel with the sunlight. So, making Hawaii”¦ they’re really exposed right now in trying to make it.
Werman: So, Borschberg and the whole team--I mean, this is historic is what you’re saying?
Hansman: If he makes it, he’ll essentially double the solo endurance flight record. And it’s really tough, just physically tough, in terms of the temperatures on board. There’s no pressurization in this airplane, so he’s got oxygen when he’s at altitude. But the temperatures will be down, -20 to -30 at high altitude and then it’ll get hot when he gets low. He’s got to go basically five days without any sustained sleep. And that just presumes there’s no weather problems. Then if he has a technical problem with the airplane, it’d be tough.
Werman: The pictures we’re seeing are pretty incredible. The wings on that plane and the lights along the wings--I mean, they’re big wings, a lot of lights on them. I assume there has to be a lot of solar panels to get enough energy to power the plane, but is the trick here getting the ratio of the solar panels to the plane weight just right in order to get it off the ground and be efficient?
Hansman: Well, it’s not so much about getting it just right. You need to get it to work, period. So, in order to make the wings big enough to get enough solar panels to be able to charge up the batteries, they’re so big and need to be so light that they become flexible, and they can be so flexible that in certain conditions the wings may break. So you’re really, like I said, pushing the envelope in the technology of wing construction; you’re pushing the envelope in the technology of the battery system and the power system; you’re pushing the envelope in terms of the physical capability of the pilot; and you’re pushing the envelope in terms of having that weather window that’s open enough to make it.
Werman: I’m sure the Wright brothers had to consider these things when they were innovating their fossil fuel airplane. But, I mean, does that mean we will see a solar-powered plane in commercial use in the future someday?
Hansman: I think the technology, or just the physics, don’t really work in order to have an airplane that would be able to fly solar-powered missions. So, to carry humans, it’s really tough. To carry humans with payload is even tougher. I do think you’ll see solar-powered airplanes that are used for unmanned airplanes, but probably not many manned airplanes.
Werman: John Hansman, professor of aeronautics and astronautics at MIT. Thank you for your time.
Hansman: No problem.