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The Physics of dragon flight possible

  1. Nov 25, 2015 #1
    So let's take a dragon, not a godzilla sized one because I'm trying to be realistic.. but say horse sized, roughly 1 ton in weight,
    or something about wolf sized so about 150 lbs
    They have 2 wings, 1 tail, 2 legs, 2 arms, and a head... because headless dragons are no fun.

    how large would the wings have to be for powered flight and what tail shape would give the dragon the most energy efficient flight if the dragon wanted to behave like an eagle (swooping and coming up again)

    no these dragons do not breathe fire/ are magical.. I want a pure realistic answer
     
  2. jcsd
  3. Nov 25, 2015 #2
    A 150 pound flying dragon fly - and you're trying to be realistic. I think you have failed.

    Insects, especially flying insects, don't scale up that far.
    But let's say we go for a 16 foot wingspan. You'll run into two problems right away. The first is that insects don't move their wings as birds do, but if you scale them up, they better. But even with bird-like flapping, there is a problem with the strength on the wing material. You're going to need to beef up the wings - they won't look exactly like a dragon fly.

    It might be better to start with an eagle, scale it to 150 pounds, and then make it look cosmetically, like a dragon fly.

    Or adapt a 150 pound remote control craft to look like a dragon fly.
     
  4. Nov 25, 2015 #3
    The problem is this. It's lift vs. mass.

    Take one dimension of your beast. Let's call it the radius of your beast. The lift of the wings depends on surface area, so lift increases as the square of the radius increases. But mass increases as the cube of the radius. So as the radius increases, mass increases faster than lift. Soon the beast can't get off of the ground. Proportionally more and more has to go into the wings to get enough lift. Then you have further problems. Big wings can't beat when the beast is standing on the ground: there isn't enough room. The biggest birds have real difficulty launching themselves.

    As for the most efficient shape, birds and pterodactyls and bats should be pretty much there already.

    The largest known flying creatures are a group of pterosaurs named azhdarchids, extinct flying reptiles that existed during the age of the dinosaurs and died out at the end of the Cretaceous. Estimations of the wingspan of the largest species likeQuetzalcoatlus and Hatzegopteryx exceed 10 m (33 ft), with less conservative estimates being 12 m (39 ft) or more. Mass estimates for these azhdarchids are on the order of 200–250 kg (440–550 lb).[6] Golly! So those dragons could exist. There have also been 150 lb flying birds.

    https://en.wikipedia.org/wiki/Argentavis
     
  5. Nov 25, 2015 #4

    a dragon... not a dragon fly..
    a reptilian dragon
     
  6. Nov 25, 2015 #5
    Sorry. I guess I was trying to be too realistic.
    Dragons are pretty fat. Maybe you should start with a dragon-shaped helium balloon.
    Other than that, the only difference in the discussion between dragon and dragon fly is that dragons have never flown.
    Perhaps you'll settle for a pterodactyl: http://calteches.library.caltech.edu/3471/1/MacCready.pdf
     
    Last edited: Nov 25, 2015
  7. Nov 25, 2015 #6
  8. Nov 26, 2015 #7
    Look up Pterosaurs.

    They were flying reptiles that lived about 228 to 66 million years ago. They had a wingspan up to 10 meters (34 feet) and weighed in 145 kg (320 lbs).

    These creatures were estimated to fly over 100 kph.

    Perhaps they would make a good starting point.
     
  9. Nov 26, 2015 #8

    DaveC426913

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  10. Nov 30, 2015 #9
    Insects are limited mostly in size by the concentration of oxygen in the atmosphere, not physics of flight, there have been gigantic insects in the past.

    These dragons, do they have to exist on earth? Earth has a pretty thin atmosphere and pretty high gravity.
     
  11. Nov 30, 2015 #10
    The only reason that I mentioned insects was because I misread the OP. Insects also don't scale up in terms of their body structures. In general, wing loading does not scale. For constant wing loading, you need wing area proportional to mass.
     
  12. Dec 1, 2015 #11
  13. Dec 1, 2015 #12
    I guess the reason why dragons in fairy stories frequently are guarding treasure is so the hero has a reason to try to tackle the beast.
    If there was no treasure to be had, I reckon most sane people would prefer to get the hell out of the way instead risking incineration and dismemberment.
     
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