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Solar Impulse Plane Begins Epic Global Flight

Posted by samzenpus on from the as-far-as-the-sun-will-take-us dept.

An anonymous reader sends word that the Solar Impulse 2 airplane has begun its attempt to fly round-the-world powered by nothing but the sun. "A record-breaking attempt to fly around the world in a solar-powered plane has got under way from Abu Dhabi. The aircraft — called Solar Impulse-2 — took off from the Emirate, heading east to Muscat in Oman. Over the next five months, it will skip from continent to continent, crossing both the Pacific and Atlantic oceans in the process. Andre Borschberg was at the controls of the single-seater vehicle as it took off at 07:12 local time (03:12 GMT). He will share the pilot duties in due course with fellow Swiss, Bertrand Piccard. The plan is to stop off at various locations around the globe, to rest and to carry out maintenance, and also to spread a campaigning message about clean technologies."

7 of 65 comments (clear)

  1. Five months? by DrXym · · Score: 2

    That's a really long time whether it is solar powered or not. If they're waiting for windows as the article says it suggests this plane runs a serious risk of having the crap kicked out of it by the weather when it attempts to fly certain legs.

    1. Re:Five months? by bsDaemon · · Score: 4, Interesting

      When SI1 did the trans-american flight, they had a stop-over at the Smithsonian's Udvar-Hazey annex out near Dulles and I went to go see it. I got to meet Bertrand Picard, which was really cool, got to touch the plane, and it was also a good excuse to go and see the rest of the collection.

      With this aircraft, we're talking about something that has the weight of a car but the wingspan of a commercial long-haul airliner. It is largely constructed out of carbon fiber, and with proportions like this I would assume that sufficiently strong winds could cause it to snap. There are also the stop-overs for educational and marketing purposes (such as spending 3 days at Dulles with the first plane 2 years ago), as well as rest and recuperation time for the pilots. They have a large ground crew, engineering team and marketing team that moves with them. It's kind of like picking up the circus and moving it to a new city and trying to get there in time before your elephants, which are on a different train.

      That said, it's one of the coolest things I've ever gotten to see in person, and Bertrand Picard is an amazing guy, from an amazing family. His grandfather was a high-altitude balloonist and scientist who inspired Professor Calculus in Tin-Tin. His father went with Challenger Deep to the bottom of the Marianas Trench. His uncle was also an explorer, Jean Picard, after whom Jean-Luc Picard of Star Trek was named. The idea for this plane came about after nearly running out of fuel during an around-the-world balloon flight in the 1990s.

      Whether we'll be seeing solar air transport on a commercial level in my lifetime or not, they're definitely attacking various engineering, scientific and social problems in a high-profile way.

    2. Re:Five months? by brambus · · Score: 2

      Whether we'll be seeing solar air transport on a commercial level in my lifetime or not, they're definitely attacking various engineering, scientific and social problems in a high-profile way.

      I love the forward thinking and positive view of technology including solar power, but there's no way there are ever going to be purely *directly* solar powered commercial airplanes in the future. The power requirements are just so far removed from being able to fly at anywhere near the speeds you may want to travel at to make it a viable mode of transport. Just to give you a taste of the energy requirements needed for air travel, let's have a look at a modern airliner, .e.g a Boeing 777-200LR. From experience, I can tell you that its engines run at about 40-45% of maximum rated sea level thrust in cruise at a speed of about M0.84, which at 35000 ft pressure altitude comes to around 480 knots true air speed or about 250m/s. Max sea level thrust on the GE90-115B is ~500 kN, so at say 40% thrust those engines are producing about 400 kN total. As you know, work = force x distance and since power = work / time, the power consumption required, just to keep the airplane in cruise is 400000 x 250, or about 100MW. Now assuming even a 100% efficient solar panel (about 1kW/m^2), you'd need about 100000 square meters of panel, or about a third of a kilometer on a side. Meanwhile, the actual top-down looking surface area of a 777 is approximately 2 orders of magnitude less than that. And any increase in surface area beyond that dramatically increases drag and the resulting energy requirements. And that's with a hypothetical 100% efficient solar panel (in actual fact, best lab results are about 35-40% efficient). Put simply, even from first principles, the idea of a solar-powered commercial airplane is just a non-starter.

  2. Solar constant is 1kW/m^2. No way around that. by renergy · · Score: 4, Interesting

    Given the solar constant, i.e. the fact that there is at most 1kW per square meter of solar irradiation, there is no way this kind of planes could be used to air transport as we know it. To make the plane more powerful, way too much wing area would be needed, which would in turn reduce the speed etc. So, unfortunatelly, planes powered directly with photovoltaic panels will always be very limited in the weight they can carry. There are still applications for such kind of planes, though. (the 1kW/m^2 corresponds to a clear sky, the plane perpendicular to the impinging fotons, near the equator around noon, so the sun rays go almost perpendicularly through the atmosphere AM1.0 spectrum - simply the most favorable conditions). Photovoltaics (on a large area) powering the synthesization of hydrocarbons for conventional airplanes, renewably from air CO2 and water - that's completely different story. But it is not what this project is about.

  3. Re:Photosynthesis thumbs up! by Anonymous Coward · · Score: 2, Insightful

    Yeah, it's hard to imagine how this technology matters to most aircraft. Don't get me wrong, it's an impressive demonstration of how far you can go on a tiny amount of power, and there are a few applications where it might matter (e.g., high altitude drones). But one look at the amount of power it actually takes to push a commercial airliner (e.g., one Boeing 777 engine produces ~75 megawatts at full throttle) and you realize solar power is completely irrelevant for that application.

    These kinds of articles where it's implied that someday we'll all be flying around in solar-powered planes are silly. It means they haven't done the math. Heck, even if you covered every square metre of a plane with solar cells you couldn't collect enough power. There's not enough there. Even if you charged up batteries from ground sources you couldn't carry enough storage and have the plane get off the ground because of the weight. Even with an order of magnitude improvement of power density you couldn't. The only way that solar could possibly be relevant for air travel is if you used the solar power to generate chemical fuels of some kind, with all the energy losses that conversion implies, and then put that chemical fuel into the plane. Aircraft is the one power demand where we will be using fossil fuels or their chemical equivalent for a long time. Weight, energy storage density, and efficiency matters too much for that application for it to be any other way.

  4. popularize idea, not have solar airplanes by Anonymous Coward · · Score: 4, Interesting

    I think that the effort isn't about "solar powered airplanes", since, as pointed out above, 1kW/square meter just doesn't do it. It's more about "expanding the possible" by doing something unusual. There's significant value in doing something challenging.. or do you sit at home and say, "well, it's theoretically possible to go to the North Pole on foot. I can read lots of books and figure out how to do it, theoretically. So, that problem's solved. Next...."

    How many people will be inspired by the idea in general: yes, you can do cool stuff with solar power. Some will be impractical (cargo planes with solar cells), but maybe, as someone does the calculations to show that it's impractical, they'll get an appreciation for what *is* practical (dirigibles using solar power for propulsion, but not lift, if we want to stay in aviation) , and then, they'll go out and say, let's go do that. Or, for that matter, they may not go solar power at all, but you've planted the seed of curiosity in someone

    Let's not forget, too, that at least one of the pilots is an adventurer (he's already done a non-stop around the world balloon flight) from a family of adventurers (August in balloons, Jacques to the bottom of Challenger deep)

  5. Re:Why East? by jklovanc · · Score: 2

    The jet stream goes east west. Get high enough and one get a boost in speed.