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Power Technology

Solar Craft Flies Through Two Nights 156

Posted by ScuttleMonkey
from the nasa-awash-with-envy dept.
An anonymous reader writes "A solar-powered, unmanned craft has flown for 54 hours — a record for both unmanned aerial vehicles and solar craft. None before has managed to store enough solar energy to fly through more than one night. There is also a video showing the 18m carbon fiber wing craft being launched."
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Solar Craft Flies Through Two Nights

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  • more (Score:5, Interesting)

    by stoolpigeon (454276) * <bittercode@gmail> on Monday September 10, 2007 @04:46PM (#20544545) Homepage Journal
    This BBC article has good info. [bbc.co.uk]
     
    It should not be a surprise that the Global Hawk record did not stand. Look at the two craft. If a global hawk hit the zephyr it probably wouldn't even notice.
  • by InvisblePinkUnicorn (1126837) on Monday September 10, 2007 @04:49PM (#20544605)
    From Wikipedia:

    "Engouh Solar Energy (ESE) is a newly-discovered form of solar energy capable of lighting even the darkest parents' basement to the point where the average nerd can neither see his keyboard nor the inevitable typos he'll make on internet discussion boards."
  • by mweier (135569) on Monday September 10, 2007 @04:59PM (#20544745) Homepage
    Obviously solar panels feed it to maintain energy stores; however since it must store this energy in a battery of some sort, is it required that the batteries be empty when launched? If not, what's to stop someone with a major pile of pre-charged solar-rechargeable batteries from tacking one solar panel on top & calling it a solar vehicle even if it could never fully charge those during use? Not accusing these folks of doing that but just curious about how they classify solar vehicles...
    • I'm not sure why going two nights is such an achievement. Surely you charge the batteries in the first day, discharge them the first night, and then repeat on the second day and night. Unless the batteries are not fully discharged for takeoff, as you say.
      • by QuantumG (50515)
        There's these things called clouds right, and they obscure the thing called the Sun which the solar power comes from.. and, as such, no two days are the same.

      • That would require that the craft generate enough solar power to charge the batteries AND power the craft at the same time. The loss of energy in transferring from solar cells to batteries and drawing from batteries again is not inconsiderable, and the motors need to run in daylight, too.

        At 20% overall efficiency (assuming arbitrary battery losses from a 30% solar cell), you need to be able to collect ten times the operational requirements of your vehicle in order to pull off what you describe. That's qui
        • Right. I understand why flying through the night is impressive, but why is flying through a second night impressive? If on day 1 you can generate enough power to fly through night 1, why is it hard to generate enough power on day 2 to fly through night 2? Unless, of course, the battery is charged prior to take off, at which point calling it solar powered is not really accurate; solar assisted might be better.
          • by Eivind (15695)
            Your hunch is correct; the plane is charged prior to take-off, which it needs to be because on the first day it has *two* tasks, one is to charge the batteries, the other is to gain 15-18000 meters of altitude. It would be unable to do both, but manages to do one of the two.

            And that's why *2* nights is interesting -- on the first day/night cycle the plane demonstrates that it can climb to altitude without using the batteries, and that it can survive the night on batteries-only.

            On the second day/night cycle
    • by larkost (79011)
      There is a natural limiter here: batteries are very heavy and a battery-powered (heavier-than-air) aircraft is unlikely to ever get close to this record. That is something that is unlikely to change before things change enough to make this sort of record meaningless anyways.
      • by Jartan (219704)

        There is a natural limiter here: batteries are very heavy and a battery-powered (heavier-than-air) aircraft is unlikely to ever get close to this record. That is something that is unlikely to change before things change enough to make this sort of record meaningless anyways.


        Why use batteries though? What about miniature flywheels and what not? Batteries would be the last type of energy storage I'd look at for this sort of application.
        • by jtcm (452335)

          Why use batteries though? What about miniature flywheels and what not?

          You're right, flywheels can store the same energy using less mass, and can be more efficient. I suspect, though, that heavey flywheels on a light airframe would make for some difficult gyroscopic effects.

          In fact, see this page with a Flywheel vs Battery Energy Storage [axeonpower.com] comparison. It's just past halfway down the page:

          Flywheels are preferred over conventional batteries in many aerospace applications because of the following benefits

          Fl

          • The other big problem with flywheel batteries is failure. If the complicated superconducting bearing and vacum systems fail the energy could be released very rapidly. Add to that the fact that for maximum energy density the flywheel is probablly on the brink of flying apart and the potential for carnage is obvious.

          • by salec (791463)
            You can mount the flywheel in gyroscope gimbals, thus decoupling it from the airframe (and you also get a gyroscope for free :P )
    • Re: (Score:2, Interesting)

      by agingell (931397)
      The record in question actually has nothing to do with solar power. It is purely an endurance record for longest flight time under continuous power. The Global Hawk is actually powered by a turbojet engine and normal Jet A1 fuel.

      Solar powered aircraft have been quite successful for some time for instance the Pathfinder and Helios aircraft by NASA the biggest issue is to get through the night on battery power. I believe the NASA aircraft had to resort to gliding and soaring which this aircraft does not.
    • by XaXXon (202882)
      Charge as many batteries with as much power as you want - you have to get them off the ground. The problem is that right now batteries are heavy and not efficient enough. It's the same problem with getting rockets into space. You have to carry the energy you want to use later.

      This is something that will get solved - the only interesting part is 'when'. The fact that it's happening now is what's interesting.
    • by Eivind (15695)
      Nothing prevents that. But a battery doesn't contain even nearly enough energy to fly for 2 nights and 3 days. So if you did this, your plane would come back down once the battery was empty, after a few hours at best.

      The endurance-record for not-collecting-energy is the Global Hawk, it uses jet-fuel which has a lot more energy relative to weight compared to batteries, and it still manages "only" max 30 hours.

      I'm guessing the max for a batteries-only plane would be in the single-digit-hours, indeed for this
    • by LoudMusic (199347)
      It still has to heft those batteries. In my solar-uneducated-opinion, if it made it through one night and was able to recharge and make it through the next it should be able to do that indefinitely. Assuming optimal conditions. It could also take advantage of flying west in the sunlight and east in the darkness to pick up a few extra minutes of Sunlight.

      I'm wondering if there are plans to put these things in motion with cameras equipped for continual updating of surface images in populated areas. A team of
  • by Anonymous Coward on Monday September 10, 2007 @05:21PM (#20545005)
    A series of halogen lights mounted along the wings are illuminated at night to power the solar array.
  • What the? (Score:2, Insightful)

    by veganboyjosh (896761)

    enouhh


    What the hell kind of spelling mistake is that? Come on editors, at least READ the edited summary...
  • Does this bring us closer to personel flying cars, that have been promised to us for decades?
  • by CrazyJim1 (809850) on Monday September 10, 2007 @05:22PM (#20545025) Journal
    During the day, it flys with the sun, to get a longer day. Then during the night, it flys in the opposite direction in order to achieve a shorter night.
  • Tipping Point (Score:3, Informative)

    by Doc Ruby (173196) on Monday September 10, 2007 @05:47PM (#20545313) Homepage Journal
    This is the watershed performance for solar powered vehicles. If it can go through 2 nights, it can go through any number of them. Though we're still on the sunny side of the equinox (2 weeks prior), so there is a little more time charging in the sunshine than discharging in the darkness.

    When a vehicle can go 24h on only 12h prior charge, that will be the next major milestone. Still not enough for uninterrupted travel past a latitude where nights are longer than a whole couple of days (depending on the battery - a yearlong discharge battery would be good anywhere with current performance).

    The next parallel milestone is automated rechargers leaving ground charging stations to recharge the permanently aloft vehicle in flight.

    After that, there's not a lot more demand for improvement, except overall efficiency for carrying heavier loads and more demanding equipment.

    Like a network of these permanently in high atmosphere propelling solar sails through the solar system and down to blimp spaceports.
    • Re:Tipping Point (Score:4, Informative)

      by XaXXon (202882) <xaxxonNO@SPAMgmail.com> on Monday September 10, 2007 @06:14PM (#20545595) Homepage
      Mathematically that's not quite true. If it had some amount of initial charge it could be using some percentage of that in order to make it through each night. Perhaps that number is 50% each night :)

      I don't know if that is the case here.. just saying that it doesn't necessarily follow that the plane can stay up indefinitely.
  • Helios was way cooler. It was headed for continuous flight several years ago. Unfortunately it met an untimely end. I think NASA should rebuild it and continue the work. Some of the, um, pundits, on this thread don't seem to have the faintest about how it could work, but it is an awesome concept: solar panels collect all day, generating enough power to fly and to charge the hydrogen fuel cells, which power the craft all night. And it can fly high enough to be above the weather, so the sunshine will be
  • by Colin Smith (2679) on Monday September 10, 2007 @06:00PM (#20545453)
    Replace the wings with an envelope and you can stay up for weeks.

     
    • by Eivind (15695)
      True, but you're less maneuvrable. A compromise may be worthwhile, building a plane like this, but seal it and fill it with helium. Dunno if the volume is enough that the added lift would outweigh the extra mass for sealing it though.
    • by afidel (530433)
      There's that whole problem of speed, I assume even an ultralight plane like this can make better headway then even the fastest semi rigid airships like the Zeppelin NT @ 125 km/h.
  • by kwerle (39371) <kurt@CircleW.org> on Monday September 10, 2007 @06:04PM (#20545479) Homepage Journal
    Not only did I submit this story with no type-o's, last night, but I also made reference to the previous solar powered flight that lasted 2 nights [acpropulsion.com], which this submission implies never happened before.

    Though the previous one also did gliding/non-powered flight part of the time. Still, up for 48 hours.
  • by Thagg (9904) <thadbeier@gmail.com> on Monday September 10, 2007 @07:03PM (#20546151) Journal
    Check out this press release. [acpropulsion.com]

    AC Propulsion said that they could do it indefinitely, but their pilots got worn out.

    Thad Beier
  • Attaining altitude (Score:4, Interesting)

    by drwho (4190) on Monday September 10, 2007 @07:58PM (#20546625) Homepage Journal
    Like many space and exotic aircraft, it must have to expend a lot of energy to get to its cruising altitude. Once that's done, conditions should become easier. Would it be considered 'cheating' to launch such a perpetual flying machine with an assistance device? That could be either disposable batteries that are jettisoned when discharged, or some chemcal rocket engine, or a jet engine, or have it launched from an aircraft.

    Insolation is going to me much better at high altitudes. I just hope the photovoltaic cells are designed to take advantage of the increased amount of energy available in the UV spectrum. How about filling the free space in the wings with hydrogen? That might help lift a little, at least from the ground. However, there would have to be some way of dealing with the reduced pressure at operational altitude.

    There's been a lot of interesting improvements in PV efficiency lately. However, most of these seem to only happen when the cell is operated at insolation far above normal. These are obtained by focusing the sunlight. Unfortunately, all of the technologies I know of which could do this are heavier than simply adding more, less efficient cells which operate at normal insolation or the slight improvement that high-atmosphere flight provides.
    • by jeti (105266)
      I think the ultimate goal is not to establish a record, but to
      use these planes as communication links or surveillance platforms.
      So who cares how you get the bird up as long as you can do it on
      short notice and with acceptable costs?
    • by mks113 (208282)
      Hang it under a balloon to get it to altitude. You'd lose a bit of altitude when it launched at zero forward speed though...
  • In the video, the props both appear to turn CCW (viewed from behind the craft) and turn very slow. I wonder why they didn't go with props that turn in opposite directions?
  • Better check the record books. I'm sure that this is the first heavier-than-air craft to do this. Unmanned ballons have stayed up for much longer and I sure a remote controlled Zepplin could stay up much longer.
    The article says that it landed 54 hours later, but didn't specify where. If this thing doesn't have enough power to keep up with the winds above a city, it won't be much use as a satellite replacement. However if it can keep up and fly in circles above the weather it'd make an ideal replaceme

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