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The Military Transportation

Liquid Hydrogen Powers a UAV For a Cool 48 Hours 72

Posted by Unknown Lamer
from the spy-longer dept.
An anonymous reader writes "While liquid hydrogen may not be a mainstream fuel for drones, the aerospace industry has said it holds the promise of flight endurance on the order of days, seemingly just another far-fetched aerospace industry pitch ... until now. The Naval Research Laboratory just announced that the Ion Tiger, a diminutive 37-pound airplane with a 17 foot wingspan, flew for 48 hours and 1 minute on liquid hydrogen and a fuel cell (anyone else notice the oddly specific duration? Guess it's better than 47 hours 59 minutes). This is a dramatically different scale than the liquid hydrogen powered 150 foot wingspan Boeing Phantom Eye and 175 foot wingspan AeroVironment Global Observer, which have yet to live up to their multi-day endurance projections. Interestingly enough, the well-known Global Hawk only has an endurance of 33.1 hours, which barely cracks Wikipedia's list of notable UAV endurance flights. Of course, solar-electric airplanes have flown for two weeks continuously, but that sure seems like refueling!"
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Liquid Hydrogen Powers a UAV For a Cool 48 Hours

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  • by Anonymous Coward on Friday May 10, 2013 @02:37AM (#43682633)

    How about you try to use units that make sense? Here's a diagram that illustrates the sillyness https://7chan.org/sci/src/132255181954.jpg [7chan.org]

    • by maxwell demon (590494) on Friday May 10, 2013 @02:55AM (#43682709) Journal

      Yes, they certainly should have used "172.86 kiloseconds" instead of "48 hours, 1 minute". Those odd factor-60 minutes and hours should die. It's not that hard to remember that a day is 86.4 kiloseconds and a year is about 31.5 megaseconds, after all.

      • by julesh (229690)

        What are these archaic "day" and "year" units you're using? I haven't felt the need for units based on the orbital mechanics of one single planet for a significant fraction of a gigasecond. And besides, 10*PI megaseconds is a much more interesting period of time. :)

        • Re: (Score:3, Interesting)

          by maxwell demon (590494)

          Actually a good way to remember the length of a year is to remember that pi gigaseconds give (almost) a century.

      • Those odd factor-60 minutes and hours should die

        There has been an attempt at decimal time [wikipedia.org] during the french revolution, but it did not catch up

    • by Anonymous Coward

      Surely it was to meet a contract stipulation: "...shall fly for a period exceeding forty-eight (48) hours..."

  • The QinetiQ Zephyr laughs aloud at this with its two week high altitude endurance record. There are several two day platforms out there, look harder ;-) http://www.suasnews.com/2010/07/470/after-14-nights-in-the-air-qinetiq-prepares-to-land-its-zephyr-solar-powered-unmanned-aircraft/ [suasnews.com]
    • by Sique (173459)
      To quote the blurb you are replying to: "Of course, solar-electric airplanes have flown for two weeks continuously, but that sure seems like refueling!"
  • by Anonymous Coward

    Someone please come up with a small Arduino solution to shoot them down.

    • Re: (Score:2, Funny)

      by Anonymous Coward

      I'd suggest some sort of catapult. Although I'm not sure Arduinos are the best type of ammunition.

    • by T-Bone-T (1048702)

      So it is OK to shoot down a plane just because it doesn't have a person in it?

      • So it is OK to shoot down a plane just because it doesn't have a person in it?

        That depends, are there a lot of people under it as well?

  • Of course, solar-electric airplanes have flown for two weeks continuously, but that sure seems like refueling!"

    Come on, that's terribly unfair! Refueling as you fly is not the same as having to return to base...

    • by drinkypoo (153816)

      Come on, that's terribly unfair! Refueling as you fly is not the same as having to return to base...

      It's not refueling at all. Refueling would be swapping batteries. This is recharging. It's foolish to try to describe recharging as refueling when there's already a separate name for each. Or, in this case, it was prevarication on the part of the commenter.

  • by oodaloop (1229816) on Friday May 10, 2013 @05:25AM (#43683149)
    The Global Hawk is the size of a 747. The Ion Tiger is a small lightweight drone with a 17" wingspan. And the Phantom Eye is large at 150" wingspan, but also described as lightweight. Comparing flight duration seems a bit unfair. Anyone have a better idea how to properly compare efficiency of engines?
    • by Anonymous Coward

      For 'regular' turbine engines this is typically done with the 'specific thrust' and 'specific fuel consumption'. With these this allows you to make more reasonable comparison between engines of whatever size. Of course performance characteristics such as velocity of the plane etc should be the same.

    • by Sique (173459)
      While the Global Hawk surely is large, it's a far cry from a 747. It has a wingspan of about 130 ft and a length of 48 ft. Compare that to the 211 ft wingspan and 230 ft length of a 747-400!
    • by T-Bone-T (1048702)

      The Global Hawk isn't anywhere close to the size of a 747. A 747-8I is about 4x taller, 4x longer, 4x wider wingspan. It is a big drone but not especially large compared to other aircraft.

    • by wagnerrp (1305589)
      Global Hawk is a turbofan. Phantom Eye is a turbocharged piston. This one is electric. As a general rule, turbines are more efficient than pistons, and fuelcells/electrics are more efficient than turbines. The more important trait here is cruise velocity. The electrically powered Ion Tiger is going to be much slower than either of the other two, and thus will inherently consume considerably less fuel.
      • As a general rule, turbines are more efficient than pistons, and fuelcells/electrics are more efficient than turbines.

        Fuel cells can be anywhere from 1% to 90% efficient. In this case it's probably nearer the 90% limit, but that's not the general case.

        • by wagnerrp (1305589)
          90% seems awfully high. I was under the impression typical performance was around 40%-70%, depending on the chemistry and materials.
          • by tlhIngan (30335)

            90% seems awfully high. I was under the impression typical performance was around 40%-70%, depending on the chemistry and materials.

            In general, the limiting factor is the quality of the hydrogen - the oxygen can generally come straight from the atmosphere. In this case, it's pure hydrogen stored as a liquid, so fuel cells tend to be fairly efficient.

            Take Apple's fuel cells powering their data center, and they're running off natural gas, which is 20% carbon for the most part (by stoichiometry) which is impur

  • by gatkinso (15975) on Friday May 10, 2013 @07:39AM (#43683741)

    It flies at 300 knots and weighs ~30,000 lbs (~14,000 kg).

    I worked on the NASA Global hawks for a few years. They are incredible aircraft and certainly not in the class of the toys it is being compared with. Predator comes close (I was on an effort to put a sensor on the NASA Predator but funding got yanked) but Predator doesn't have nearly the capability of Global Hawk.

  • by Anonymous Coward

    Yeah, I've spent some quality time navel gazing myself.

  • The liquid hydrogen can be used to cool the infrared sensors as well.

  • Not sure that says much about the power system.
    The plane appears to be very close to a sailplane. Drop the weight a bit and i think it would run on watch batteries and thermals.

    17 feet is a lot of wing for 40ish pounds of airplane.

    hmm, can we make a powered glider that can find a big thermal and reverse the circuit to recharge a battery in a dive?

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