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This question already has an answer here:

I have noticed that one thing that is very common among steampunk airship art is that the size of the decks beneath the gas chamber is outrageously larger than that of the real world.

Example:

enter image description here

Attribution: cdna.artstation.com 2019

enter image description here

Attribution: AngMoKio - Own work, CC BY-SA 3.0 id:10594526

Let's assume we are in a society that is around the 19th century in terms of technological development, so I believe some ultra-light materials might not be an option. Let's also assume that this world is much richer with helium and other light gasses than Earth, so running out of them is not a problem.

I'd like to ask if there is a way to achieve the size of the "decks" shown in the first picture, using no physics-alternating methods. These decks would be loaded either with cargo or military gear. Would the size of the bag be so incredibly immense it would be too much to justify it's use?

Because of the dangers of using hydrogen on an airship (especially a warship), I would rather use helium, but that is not as light. I know making the atmosphere denser is also a possibility, but that messes with a lot of other factors which I would rather not change.

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marked as duplicate by user535733, Chickens are not cows, SZCZERZO KŁY, JBH, Cyn May 22 at 14:38

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ There already is a gas lighter than helium, helium is twice as heavy as hydrogen & hydrogen is the most abundant element in the universe. It was most commonly used in giant airships, right up until the Hindenburg disaster.. You won't be able to produce an artificial gas lighter than Hydrogen without copious amounts of handwavium. $\endgroup$ – Trotski94 May 22 at 12:28
  • $\begingroup$ Hydrogen's been around (in use) since 1671, made by reacting iron with acids. $\endgroup$ – Chickens are not cows May 22 at 12:38
  • $\begingroup$ Are you willing to change the atmosphere to be denser? $\endgroup$ – ratchet freak May 22 at 13:14
  • $\begingroup$ @Trotski94 Helium is 4 times as heavy as Hydrogen, as a free floating gas Helium is twice as dense as H2 but that's not quite the same thing. $\endgroup$ – Ash May 22 at 13:47
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    $\begingroup$ I have voted to reopen. While the linked dup question does touch on the size issue, it's really about steam engines. Now that the OP has removed the extra question about steam engines from this post, it's just about size ratios, and is no longer a duplicate. $\endgroup$ – Cyn May 23 at 13:43
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Note that this answer was made in reference to the question “Is there a way to make a steam engine powering a dirigible work?” which was later edited out.


NOTE: You asked two questions, one about deck size and one about engines. I answered the latter because the answer to the former is a flat ‘no’, which isn’t really interesting.

Short answer? Not really

Long answer: Not really, unless you’re willing to accept a different definition of ‘steam engine’.

See: the critical issue here is power to weight ratios. We can make an arbitrarily large envelope for our dirigible (probably a rigid frame zeppelin, actually) that will be able to lift the weight of our steam engine plus all of its water and fuel stores, that’s not an issue. We can further reduce the weight needed by switching from a traditional clouds-of-steam-belching open steam engine to one with condensing coils and a closed water loop.

But that envelope would still be huge, and the power produced by a mechanical steam engine would be too small to effectively push it in anything but a dead calm (and even then it would be slow).

But what about if we don’t use a steampunk rod-and-piston arrangement?

Time for a digression.

Diesel trains don’t actually use diesel for motive power, for the most part. This is because Diesel engines are really, really efficient if made to operate at a particular speed, but trains often change speed. So what the trains do is generate electricity using a Diesel engine, then use that electricity to drive electric motors to move the train. Because the Diesel engine can be built to work at very strict tolerances it can be made very efficient.

Back to the point.

We can build a closed loop steam engine that actually just rams steam through a steam turbine to generate power, then use that electricity to power the propellers. Because it’s closed loop we won’t be losing water, because it’s designed for one mode of operation we can make it really quite efficient, and it still has some of the advantages of a traditional steam engine (notably you can use it with any fuel that will burn hot enough). If we use titanium for the piping and keep the generator quite small then our power-weight ratio can be vastly improved, potentially even to the point of being viable!!

Of course: using electrical motors stops it being quite the victoriana cast-Iron-and-belching-pipework that defines the Steampunk genre, but technically you’re using steam, so...

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  • $\begingroup$ Hi, i have added a note explaining why your answer does not answer the question any more. I would leave this answer up as the OP has found it useful, though i might suggest also reposting this onto the question this was marked as a duplicate of or having a moderator translocate it there (obviously then removing the note i put on the answer here as it wouldn’t be relevant there). worldbuilding.stackexchange.com/questions/67461/… $\endgroup$ – Liam Morris May 23 at 18:21
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Your airship looks about the size of a galleon, which range from 500-2000 tons in weight. If you take a light galleon at 500 tons, this is 2.5x the weight of a Hindenburg Airship.

This means you need 2.5 times the size of a gas cell, about 500 000 cubic meters for the gondola alone, not accounting for the gas bag. This of course does not match up spatially with the pictured deck size, galleons were maybe 30m long, while the Hindenburg is 250m long, even with a thicker gas cell, the bag will be more than 10x the length of your craft. You still need to keep this up somehow, without benefit of lightweight aluminium.

The steam engine should not be the issue, steam engines can be built quite light and efficient, especially if you are willing to burn petroleum. You will need a condenser to keep down on the water consumption.

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As other answers and comments have already said, the proportion of gas bag volume to gondola is going to be big even if the gas is hydrogen and the gondola is made of lightweight modern composites. Using helium (as you wanted) and wood (as per steampunk restriction) is going to make that proportion outrageously huge. Like a small ant on a football ball - american football, for the correct shape.

There's no way to solve that except resorting to magic or changing the atmospheric conditions of your planet. For the engines, I think I have a solution that's valid for your steampunk technology, even if it's sort of a frame challenge: kite rigs.

Kite rigs can be made using the same kind of cloth they used for sales, and even if they can't be made as big and light as modern ones, an airship is way easier to move than a ship - same "weight", because they are both floating, but much less drag. Also, kite rigs work the better the higher they fly, so using them in an airship is going to take advantage of the really strong winds up there. They work remarkably well with cross winds, and I'm convinced they would yield a far better performance than any kind of engine you can build with handwavium-free steampunk technology - they are probably a viable competitor against modern dirigible propellers.

I know that you didn't want to use hydrogen, but besides offering much better performance, and thus the least skewed ratio between gas container and payload, it's far more believable since hydrogen has been known and used from the middle ages. By using kite rigs you avoid its most known problem: the risk of fire. No engines, no sparks - just beware of the kitchen and smokers. :P

I'd put a mast with a periscope and the kite rig all through the gas bag so that the kite can be deployed from the upper side of the gas bag while controlle from the gondola on its belly.

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  • $\begingroup$ I've done some basic math, coming to the conclusion that to lift a gondola that weighs 500 tons, I would need around 450 000 cubic meters of helium, which would make the dirigible around 430 meters long, should it be 50x50 meters in width and height. (Hindenburg was 41 meters) If I am to be honest, that does not seem to me as outrageously huge. It is less than double the length of Hindenburg and allows to carry a 500 ton gondola. I also calculated this using hydrogen, but the difference wasn't that big, only about 30 meters. I am not sure if my math was off, though. $\endgroup$ – D. Daniels May 22 at 14:39
  • $\begingroup$ @DDaniels A 500 tons wooden ship should be less than 50 meters long, if it was to retain its normal proportions of beam and draft. It's going to look tiny compared to the gas bag, just like every airship that ever was. $\endgroup$ – Rekesoft May 22 at 14:56
  • $\begingroup$ Kite rig airship would require extremely long lines, as the upper and lower ones need to catch winds going in different speeds/directions. $\endgroup$ – Eth May 22 at 15:52
  • $\begingroup$ @Eth You can see pictures of kite rigs in the wikipedia link I provided. Sure, they are long, but victorian era technology can procure this far more easily than a ultralight steam engine. $\endgroup$ – Rekesoft May 23 at 8:05

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