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So my world is a fantasy setting (I wouldn't call it high fantasy) where a few hundred years ago a great empire invaded an island the size of Syracuse (due to overly aggressive flying natives attacking ships that sail a bit to close). When they first invaded the island they actually did quite well for wingless creatures, (the natives could only glide) but as they went farther inland the coastal mountains got higher and the advantage of gliding became ever more clear, their armies would always get destroyed before they reached the tallest ridge, to be able to get past the apparent wall the emperor declared a reward for someone who could come up with a form of airship to bombard stuff at and beyond the coastal range.

Of course somebody came up with the idea of a hydrogen filled Zeppelin, but without engines. Any form of engine would wait over a hundred years to be invented. My question is how would you land a Zeppelin (without deflating) and what would you use, instead of engines, to maneuver it? Also the culture doesn't have a good enough understanding of magic to use it for this problem.

skout
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    An airship without engine is usually initially called a "balloon", and later called "wreckage". Without a ground crew, airships simply crash. Zeppelins had 30+ laborer ground crews to catch the guy rope and haul the massive airship to the mast. Quite a few laborers were killed or maimed doing this - airships have a lot of sail area, and gusts happen. Goodyear later began using a tractor to haul (smaller) blimps to the mast. Without engines, maneuvering to the landing field's county would be a real challenge - with working engines, fly-arounds caused by gusts or misjudged winds were common. – user535733 Mar 12 '18 at 04:44
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    @user535733 is absoltely correct, especially about the "wreckage" part. The answers you're getting are clever, but they also won't work. You're 100% subject to the weather and your only way to land iis to let the gas out. – JBH Mar 12 '18 at 16:25
  • You might want to look through the answers to [https://worldbuilding.stackexchange.com/questions/8485/how-could-a-sail-powered-airship-work/8489#8489](this similar question). – Henry Taylor Mar 12 '18 at 16:44
  • ground crews are no problem, the landing just needs to be doable without engines or deflating. They will always be landing in friendly territory and there is no other air or anti-air to worry about. It taking a long time to land doesn't matter either. Is it doable? Practically? then its fine. – skout Mar 12 '18 at 20:34
  • Taking a long time to land does matter - close-to-ground is the most dangerous place for an airship. There is no time to react to an errant breeze. The longer you stay low, the more likely that errant breeze will occur. – user535733 Mar 13 '18 at 01:46
  • Then it would be appreciated if you could provide a system to land a blimp quickly without engines. – skout Mar 13 '18 at 01:51
  • Perhaps the 'reality-check' tag is too restrictive, since the concept does not seem realistic (this does not diminish it's coolness at all). You might do better with 'science-based', where you can take a bit more liberty and can handwave away a few more hard realities. – user535733 Mar 13 '18 at 02:45
  • Suggestion implemented. – skout Mar 13 '18 at 02:48

3 Answers3

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A zeppelin is floating like a boat is floating. Engineless boats can be propelled by sails or oars.

  • Sails would be possible for the zeppelin and it would need a long keel below it to allow tacking.

  • Oars or paddles which must be lifted out of the water on the forward stroke would not work; there is not an air/water interface.

    • Oars that stay in the water and propel via a lateral motion would work fine. This is sculling.

https://en.wikipedia.org/wiki/Sculling#Single-oar_sculling

Single-oar sculling is the process of propelling a watercraft by moving a single, stern-mounted oar from side to side while changing the angle of the blade so as to generate forward thrust on both strokes... In single-oar sculling, the oar pivots on the boat's stern, and the inboard end is pushed to one side with the blade turned so that it generates forward thrust; it is then twisted so that when pulled back on the return stroke, the blade also produces forward thrust. Backward thrust can also be generated by twisting the oar in the other direction and rowing. Steering, as in moving coxless sculling shells in crew, is accomplished by directing the thrust.

The pictures I found do not do it justice. My favorite sculling is the little tub-boat Lin is in in the movie Spirited Away.

As regards landing, you would land the inflated zeppelin in the same way people moor barges and boats. Someone jumps off to the land, attaches a line and then the crew use the line to pull the boat in.

For your zeppelin a crewman would be lowered on an anchor. He would make the anchor fast to something sturdy on the ground (or perhaps the anchor is a screw and he screws it into the ground) then the crewmen still aboard the airship use the anchor line to pull themselves down to the ground - either with manpower or with a winch.

ADDENDUM

I take it the anchor thing is self explanatory. Here is more on single oar sculling.

single oar sculling water taxi

The single oar is swept back and forth. You can use a regular oar this way (for example your other oar breaks). Some boats have a mooring point in the back of the boat to allow this. The pictured boat has a long oar purposefully for sculling.

The sculling oar is pushed back and forth. It is turned as it moves from side to side, so a component of the motion is forward in both ways.

sculling diagram http://archive.is/pJOua

If it is still not making sense watch some youtube videos.

So your single oar sculling airship: it would have a giant fanlike sculling air-oar off the back. This would be pulled back and forth - maybe by a team of slaves or maybe by draft animals in the ship working a wheel with mechanisms to translate rotary into lateral motion.

Alternatively you could have a row of individual air-oars set up like a Roman galley, but the oar stroke would be flat against the wind on the backstroke and then blade forward (to minimize air resistance) on the return stroke.

Of course the fans would be painted with patterns specific to the allegiance of the ship, or maybe with a decoration particular to that ship.

Willk
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  • So could you please give abit more information on how this would work? – skout Mar 11 '18 at 23:13
  • With air it would probably be easier and more efficient to "row" and simply rotate the "air oars". This is because lower density of air means the oars would have much higher aspect ratio (be flatter), so the drag difference between rotation of the oar would be huge. Since the motion would be simpler than in water, it would be simple to make a mechanism to auto rotate the oars. – Ville Niemi Mar 12 '18 at 02:35
  • Sails extract energy from the difference between the water's speed and the air's speed. An airship doesn't have any speed difference to extract energy from, so sails are useless. "Sculling" would work, but your "oar" would be a gigantic fan, probably best operated by a team of "rowers". – Mark Mar 12 '18 at 06:11
  • @Mark - I am happy you put that up about the sails. Get out a napkin and draw some vectors: wind on ship body, wind on sail, air resistance of sail, ship, keel. What do you find? – Willk Mar 12 '18 at 12:57
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    @Willk, I find that if I drop the water friction vectors, the ship moves at the speed of the wind in the direction of the wind. If I drop the wind friction vectors, I find the ship moves at the speed of the water in the direction of the water. It's only if I have both the water vectors and the wind vectors that the ship goes in a controllable direction. An airship doesn't have the water vectors. – Mark Mar 12 '18 at 18:19
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    @Willk, sails are only able to move a boat in any direction other than downwind because of the resistance of the keel against the water, which can be used to redirect the force provided by the wind. There is no equivalent for an airship unless you can extend a "keel" so far down (or up, I suppose), that you find a wind layer moving in another direction, but even then winds don't vary in direction that much. Additionally, given the difference in density between water and air, an air-keel would need to be enormous to generate equivalent force. – Keith Morrison Mar 12 '18 at 20:44
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There were Chinese man-powered paddle wheel boats and ships for hundreds of years before steam engines were invented.

http://www.cogandgalley.com/2009/10/chinese-paddle-wheel-ships.html1

So theoretically someone could invent a man powered propeller for airships before steam or internal combustion engines are invented.

There actually have been specially designed man powered heavier than air aircraft. Therefore man powered lighter than air airships are a theoretical possibility. I see that some have actually been built.

https://en.wikipedia.org/wiki/History_of_human-powered_aircraft#Airships2

M. A. Golding
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There's a simpler answer depending how often you need to pivot. If you only need to pivot when landing, positioning the air release valves on the sides of the inflatable would act like the oar example without the necessity of wind in your favor. Just release the left valve when going right and the left when going left. It's not going to be super-fast, but if you're landing, that's not likely a major concern.

Carduus
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  • The lifting gas in a zeppelin is not pressurized. Opening the release valves will not give you any thrust (there's a reason the release valves are on the top of the ship). The lifting gas in a non-rigid airship is slightly pressurized, but not enough to give measurable thrust, and releasing it means you also need an active pumping system to bring air in to keep the envelope inflated. – Mark Mar 12 '18 at 18:23
  • The way OP is using zeppelin gives me the impression s/he is more interested in the airship portion of the question than the rigid-frame aspect. You're correct, if we want a true zeppelin, it's not going to be pressurized. But yeah, blimps are, and even that small amount of pressure is enough to slowly turn it. Heck, there could even be pressurized balloons on the sides separate from the floaty bits that could do the deed. – Carduus Mar 12 '18 at 19:07
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    As the OP i was specifically wanting a landing system without having to partially deflate the blimp. – skout Mar 12 '18 at 20:07
  • Then the pressurized side-balloon idea is the best I have. – Carduus Mar 12 '18 at 20:49