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Theoretical limits to wing and aircraft size?
by
Andrew_W
on 13 Aug, 2012 23:43
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Is there a limit to how large a wing can be without the distances across the surfaces leading to a degrading of wing performance?
For example could a 10,000 tonne subsonic booster with a delta wing area of 60,000m^2 (say a span of 300m, average distance leading to trailing edge of 200m) fly OK in theory?
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#1
by
cleonard
on 14 Aug, 2012 00:08
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The first limit will be the cash needed to engineer and build such a gigantic thing.
The squared vs cubed relation of surface area to volume has a way of making the weight too high for the surface area to support when the scale gets too big.
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#2
by
Patchouli
on 14 Aug, 2012 03:57
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Cost and finding a place to land it would probably become limiting factors long before you'd run into any limitations of physics.
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#3
by
Andrew_W
on 14 Aug, 2012 04:09
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Cash isn't relevant to the question, which was restricted to the physics of the issue.
Landings and TO (also not on topic) would be from lakes.
In terms of area vs volume, given that such a giant would have most of its cargo (fuel for upper stage) stored in the wing itself (or externally as an upper stage), with no need for window seats, subtracting the mass of a large fuselage should push such an upper boundary very high (well into the tens of thousands of tonnes?).
Thank you both for your considerations on the physics.
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#4
by
Jim
on 14 Aug, 2012 10:02
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1. Landings and TO (also not on topic) would be from lakes.
2, In terms of area vs volume, given that such a giant would have most of its cargo (fuel for upper stage) stored in the wing itself (or externally as an upper stage), with no need for window seats, subtracting the mass of a large fuselage should push such an upper boundary very high (well into the tens of thousands of tonnes?).
1. that adds different problems and negates your premise. Hydrodynamic considerations will have a larger affect on the shape of the vehicle.
2. Not viable for cryogens. You will need a fuselage. Especially with external carriage.
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#5
by
cleonard
on 14 Aug, 2012 15:32
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I believe the limit is really wing loading. Large airplanes like an A380 or 747 are in the 600 to 800 kg per square meter range. Go any higher and your takeoff speeds just get too high. Now big delta wings don't have the efficiencies of a passenger plane but the above is a good range for BOE type of calculations. Be conservative and use 500kg/m^2.
Your 10000 ton 60000 m^2plan is actually lightly loaded. If you go with 500kg/m^2 you only need 20000 m^2. Still a gigantic plane but only one third the size.
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#6
by
Patchouli
on 14 Aug, 2012 21:41
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The Reynolds number will be different from what is normally encountered in aircraft engineering at those scales.
Not an unknown though since architectural engineers deal with this scale all the time when they have to model wind loads on a large building.
Though no one has dealt with super sonic airflow at those scales as far as I know.
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#7
by
MATTBLAK
on 14 Aug, 2012 21:55
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I wonder how well Blended Wing/Bodies fair in terms of making really, really large aircraft? I'm taking about a vehicles that could have a 1000 ton takeoff weight, taking masses of passengers and/or freight at high subsonic speed over global distances?
I've looked at the Antonov-225 and wondered about a similar concept for the A-380: six engines, highly-stretched fuselage, new wings and undercarriage etc. Probably not viable in today's economic climate.