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Science Technology

NASA Breakthrough For Solar Powered Aircraft 23

gilgsn writes "Planenews.com just received a news release from NASA's Dryden Flight Research Center about a breakthrough in fuel cell technology for solar powered aircrafts and how they used internet technology to broadcast data and HDTV video from the stratosphere above the Hawaiian island of Kauai. Their Helios Prototype could now fly through the night. I am sure that besides public communications, this will interest the military for their drones.."
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NASA Breakthrough For Solar Powered Aircraft

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  • With such a limited supply of fossil fuels, this could be the answer to the problem when we run out of them. If this process was perfected, it could be used to power cars in the future. I'm not very proficient with cars, but it seems to me that this process could later be refined and moved to cars fairly easily.
    • Not directly, but possibly with some changes or additions.

      First off, cars have a lot more resistence pulling on them. Not just air resistance like the plane, but also rolling resistance, cornering resistance (vector changes loose engery quicker than consitant travel, IIRC), not to mention that a car will probably be carrying a lot more weight (e.g. frame, 4 people, bag of Cheetos, etc)

      The biggest killer, though, is changes in velocity; this is one of the things that killed Gasoline turbine powered cars (I mean, purely turbine powered, mind you). This can be overcome however by using a "turbocharging" capacitor of sort that provides a monetary burst when accelerating that later slowly gets charged back up during driving (think Toyota Prius).

      And, of course, obligatory trolling: In SOVIET RUSSIA... Solar powered Aircraft break YOU.

  • Why not gravity? (Score:3, Interesting)

    by cperciva ( 102828 ) on Tuesday December 31, 2002 @10:51PM (#4992108) Homepage
    If I'm reading the story right (and it's 2:30 AM here, so maybe I'm not), the "news" here is that NASA has thrown a more efficient type of fuel cell onto a solar powered wing, thereby allowing it to store energy so that it can remain powered overnight.

    Why don't they just use gravity instead? These wings already have motors and propellors; at night, these could be used as generators. The energy obtainable by dropping a few kilometers -- hardly a big deal for a wing 40km up -- would be just as much as could be stored in fuel cells, and the entire system would be much simpler and cheaper.

    The NASA guys are pretty smart, so I'm sure I've missed something here; but what?
    • by GigsVT ( 208848 )
      You ever try to fly 40km up using a propeller?

      Hint: Not much air up there for such things.
      • You ever try to fly 40km up using a propeller?

        Hint: Not much air up there for such things.


        Ok, s/40/30/. This (propellor-driven) wing has been tested at that altitude.
    • yes but would you be gaining more energy then you were loosing the next day by trying to regain that alitude? Unless you have actual data your idea doesn't sound that usefull.
      • by spike hay ( 534165 )
        yes but would you be gaining more energy then you were loosing the next day by trying to regain that alitude? Unless you have actual data your idea doesn't sound that usefull.

        Actually, his idea makes some sense. Of course you would "loose" energy. The laws of physics dictate that you will, whether you store the energy in fuel cells or as potential energy. If you gain more energy than you lose, that would be a perpetual motion machine, wouldn't it?

        The previous poster's idea makes a lot of sense. If these solar powered aircraft are efficient at gliding, they would be able to glide all night and lose only a few kilometers, which could very easily be gained back the next day. I think it makes more sense than fuel cells.
        • by Anonymous Coward
          The only problem with your suggestion, is that for something to be considered perpetual motion, it would have to be entirely self powered, i.e fully generate it's own power.
          Wheras, this system utilises the sun to power it, there'fore, it is quite possible that this psuedo perpetual motion device could function.
          • I was just pointing out that the previous poster seemed to think that you should get more energy back from the fuel cells than you put into it. And that the gliding method would fail because you have a net loss of energy. Due to the solar cells, it's not a closed system at all, so it can obviously gain energy.
    • by Anonymous Coward
      a more efficient type of fuel cell onto a solar powered wing, thereby allowing it to store energy so that it can remain powered overnight.

      The need for power overnight isn't to keep it powered overnight (are you thinking payload?) so much as it is to keep the whole thing aloft. Their site or somewhere said the plane consumes about 30 kW. Obviously, you can't use the engines to produce electricity and thrust simultaneously.

      More data on Helios and fuel cells. [nasa.gov]
      • The need for power overnight isn't to keep it powered overnight (are you thinking payload?) so much as it is to keep the whole thing aloft. Their site or somewhere said the plane consumes about 30 kW. Obviously, you can't use the engines to produce electricity and thrust simultaneously.

        You could do what amounts to this by turning off the engines and just gliding down at a shallow angle (spending gravitational potential energy to maintain airspeed). I'd be very surprised if the craft would only sink a few km after gliding unpowered for up to 12 hours, though.
    • by Christopher Thomas ( 11717 ) on Wednesday January 01, 2003 @02:49AM (#4992715)
      The energy obtainable by dropping a few kilometers -- hardly a big deal for a wing 40km up -- would be just as much as could be stored in fuel cells

      This turns out not to be the case.

      Energy stored gravitationally is F*d: 10N/kg * 1e3m, or 10 kJ per kg per km.

      Energy density for conventional batteries is at least 10 times this. Energy density for chemical fuels is several hundred times this. So, for a fuel cell power storage system representing a small fraction of the craft's mass, you get much more power storage capacity than you'd get from having the craft sink and rise again.

      The main problem will be keeping the weight of the hydrogen tank down (if stored at high pressure), or the volume down enough to fit in the craft's airframe (if stored at low pressure).
      • Energy density for conventional batteries is at least 10 times this. Energy density for chemical fuels is several hundred times this. So, for a fuel cell power storage system representing a small fraction of the craft's mass, you get much more power storage capacity than you'd get from having the craft sink and rise again.

        I think you're missing the point. It does not matter at all how much potential energy is stored in a few kms of altitude. But if this craft is good at gliding, which it should be, being light with a large wingspan, it would only drop a few kilometers overnight through unpowered gliding. That could be easily gained the next day.
        • by Christopher Thomas ( 11717 ) on Thursday January 02, 2003 @02:52AM (#4997162)
          I think you're missing the point. It does not matter at all how much potential energy is stored in a few kms of altitude. But if this craft is good at gliding, which it should be, being light with a large wingspan, it would only drop a few kilometers overnight through unpowered gliding.

          I find it doubtful that it would only drop a few kilometres after gliding for 12 hours.

          Back of the envelope calculation supporting this:

          From the Helios page cited by another poster, Helios weighs 1600 lbs, and has 14 moters rated to 1.5 kW each (2 hp). This gives a power consumption of 0.029 kW/kg, or about 1.25 MJ/kg over the course of 12 hours. Dropping 10 km gives you 0.1 MJ/kg. Power used in flight is far greater than gravitational potential energy for any practical drop, even counting the fact that the motors are not perfectly efficient at driving the craft.

          In summary, you'd hit the ocean quite early trying to glide overnight.

          The builders of the craft seem to agree, as the project page mentiones fuel cells being _required_ for operation through the night.
  • Helios -- way cool (Score:3, Interesting)

    by MacAndrew ( 463832 ) on Tuesday December 31, 2002 @11:21PM (#4992209) Homepage
    Apple Computer did a nice piece on Helios [apple.com] -- self-promotion, but it's still nice.

    I don't think the military will be *too* interested in Helios. A very easy target to shoot down! The Predator is a lot faster, and I'm pretty sure they lost at least one to hostile fire in Afghanistan. On the other hand ... it would be useful for peacekeeping functions such as maintaining surveillance over [region] for long periods of time at low cost, such as to monitor (ahem) an arms control agreement. And I suppose it could drop bombs on things, though I'd rather it didn't.

    Now with Helios, that unending 14-hour transoceanic flight you complained about really could be unending. You could just have the thing endlessly circling the globe, weather permitting.
    • Cancel that (Score:3, Informative)

      by MacAndrew ( 463832 )
      Forget what I said about getting shot down and weather. This thing flies higher than both. My eyes apparently skipped over the subhead of the Apple article:
      Powered by the sun and controlled by Power Macs, the ultralightweight Helios aircraft shattered the world altitude record in August 2001 when the remotely-piloted vehicle climbed to more than 96,500 feet (29,421 m.) -- three times higher than most commercial jets -- in a test flight over Hawaii.


      HAPPY NEW YEAR
  • by js7a ( 579872 ) <james @ b o v i k . o rg> on Wednesday January 01, 2003 @01:38AM (#4992509) Homepage Journal
    Their Helios Prototype could now fly through the night.

    Not yet; that regenerative cell endurance upgrade is scheduled for completion by Summer 2003.

  • When can I buy one? (Score:2, Interesting)

    by joelt49 ( 637701 )
    Seriously, it would be a cool toy, to float above you. Think of the potential implications: parents could buy one for their teen-age kid(s) and have it watch him/her/them to see where they go :)
    Another idea: what about using it to generate electricity here on the ground? If we can get these things up in the air indefinitely, then maybe we could use the excess solar power, combined with the gravity idea above, to generate excess power. Not sure how efficient that would be, though. Eh, every bit helps ;)
  • by Animats ( 122034 ) on Thursday January 02, 2003 @02:21AM (#4997071) Homepage
    Here we have a commercial project [skytowerglobal.com], done by a private company [aerovironment.com], and partially funded by the Japanese Ministry of Telecommunications. And there's NASA, taking the credit. [planenews.com]

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