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OT: calculating airship volume
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I'm no mathematician, but I need to know the answer to this.
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Good job you added this caveat, because most people here were operating
on the basis that you were...given the fuel tank capacity situation of a
few months ago...
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The Hindenburg airship was just over 800ft long and 135ft in diameter
and contained seven million cu ft of hydrogen and had a payload of 123
tonnes.
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If it was a cylinder then that is a internal volume of approx 11.5
million cu ft.
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Assuming that it's a cylinder (which it isn't, quite), what dimesnions
would it need to be, to carry double that quantity?
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Your actual rigid airship or dirigible is carried aloft by gasbags within
the structure - it isn't filled out to the skin like a balloon. You can't
just dial up an increased volume as a simple multiple of the weight you want
to carry. When you make the thing bigger, you'll make it heavier, and then
you'll have to make it bigger again to carry the extra structural weight,
and so on. The dry weight of the Hindenburg was about 130 tons.
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Simplest answer - Twice as long. However I am sure there are more elegant
engineering solutions!
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Also, assuming it carried 14 million cu ft of helium rather than
hydrogen, what would the useful payload be?
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helium is about 92% of that from hydrogen so perhaps 123 x 2 x 0.92 =
226 tonnes.
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If I remember correctly from my old college days. The actual volume of gas
inside the H/burg was never really calculated to any degree of high
accuracy. The biggest problem was that the rigging and frame work displaced
so much, but no one actually knew how much.
So really, I reckon it's down to best guesses ;o)
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Using hydrogen instead of helium in the Hindenburg was calculated to have
given it about 8% more lift, so to double the lift, you'd need, very
roughly, 15 million cu ft of helium. This would give you around 480 tons of
lift. Th carry a payload of 250 tons, you'd need a stucture weighing no
more that 230 tons, but big enough to hold that volume of gas.
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Two words:
Carbon fibre.
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One word: lightning.
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ISTR that AV8Bs had composite wings containing CF. Dreamliners have
huge quantities of structural and skin CF.
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They've had to do a lot of work to get around it.
A better answer might be blow-moulded titanium frames supporting a
metallised mylar skin - the forces on an airship are quite different from
those on a heavier-than-air aircraft.
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Don't forget the geodetic construction of the R100. Chief designer was
Barnes Wallis.
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And the Chief Calculator was Neville Shute Norway. The girders of the R100
were each made of three 4" duralumin tubes, which were rolled up from flat
strip and rivetted along a helical seam. The calculations for the sizes and
stresses were done by teams of guys with pencils and paper. Ths was all
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And the extra large cylindrical slide rule, don't forget the ELCSR.
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over 80 years ago, and there have been improvements in materials and
techniques since.
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Precisely what I was thinking. That said, it's remarkably hard to better
the basic airframe design used by the later Zeppelins and the R100. I
mean, modern materials etc would effect a weight saving, but not a vast
one. The basic Zeppelin design was so simple that it's quite hard to
improve upon.
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genuinely, from Platy's post yesterday, until this one, I thought by
R100, you were referring to a BMW.
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Where you can save a lot of weight these days is in the interior
fittings, radios, engines, etc etc. Especially engines - you'd be able
to build 1000bhp+ engines that are far lighter than the units used in
the Hindenburg, and you'd also mount the engines so they could be
rotated for take-off and in-flight manoeuvring.
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No, no. You could easily make a much better airship today using modern
technology than by re-using the 19th century design of the original
Zeppelin.
Granted, it probably wouldn't be much *lighter* than the height
climbers (or even the liners) were for a given volume. The "bicycle
wheel frame" is incredibly strong by weight. And there is really no
incentive to make airships that are ultra-light anyway, except for
stratospheric station-keeping, and then it wouldn't need it to be
rigid.
But you could certainly make a much stronger and more aerodynamic
airship with modern technology. Really, even the Nobilo keeled design
of the 1920's was major improvement over the Zeppelin full rigids. Gas
pressure is an even more efficient form of structure than the bicycle
wheel is. There is no reason not to use it.
Further, modern airships would generally be much fatter than
Zeppelins, giving up a small amount of speed for better structural
efficiency. Not that you would necessarily lose any speed given other
improvements in propulsion efficiency and aerodynamics.
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These two sites are essential for anyone interested in either the
British or the German airships of the 1930s
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I did originally type ' aluminised mylar over a carbon fibre frame',
then deleted it.
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I think the answer is 16.9 litres.
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42 I think you'll find
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You both err.
53 cubic feet is the answer.
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A very rough (and very likely incorrect) calculation - 214 tonnes, based on
2x123 = 246 tonnes for payload with Hydrogen less the additional weight of
the helium (approx twice the weight of hydrogen) at approx 32 tonnes.
It doesn't help that the volume is given in imperial measure and the payload
in metric. Nor does it help that, after doing the caculation, I found that
the actual payload was 123.5 tons or 125.5 (approx) tonnes. However the
difference is only small.
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