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The simplest effective method for maintaining large flying vessels is needed

My society is a pirate haven which has low technology and resources. They have jury-rigged some system to keep the fleet flying, with personal safety being pretty much an afterthought.

The challenges I came across in the story arise from ships suffering small gun combat damage and needing to get patched up. The alien environment is very challenging so doing repairs outside might need resources out of their reach, but getting large ships out of the hostile atmosphere and into a maintenance hangar has its own challenges. Keeping the outside air outside as much as possible would be best.

Factors

  • Consider a ship of $200 \times 30 \times 40$ meters long/wide/high.
  • For a hangar, pressure is equalized inside and out; temperatures are not at all equalized ($\Delta \text{T}=380$°C)
  • No computer technology
  • No fictional technology beyond of what is stated here.
  • Advanced thermal insulating materials have been developed (a very simple aerogel equivalent)
  • Pumping air into a hangar is an option but they certainly would work nonstop on a solution which avoids the very long time that would take
  • They have suits to work outside but again, this would be ridiculously cumbersome and undesirable. Poor outcomes are likely, they would work diligently on an alternative.

How would a civilization maintain large vessels in a hostile climate?

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  • $\begingroup$ What kind of vessel are we talking about? A spacecraft, wet navy, airship, something that blurs the lines? How large is large? Surface area is going to be a factor. $\endgroup$
    – Ash
    Mar 5, 2022 at 0:54
  • $\begingroup$ @Ash Zeppelin-sized craft. Likely multiples of them at a time after any conflict. $\endgroup$
    – Vogon Poet
    Mar 5, 2022 at 0:57
  • $\begingroup$ If this is an airship in a dense atmosphere, the lifting gas can be a breathable mixture, allowing fixing damages from inside the skin. $\endgroup$
    – user35577
    Mar 5, 2022 at 2:11
  • $\begingroup$ This is true for some maintenance, yes. Eventually some outer hull will be needed? $\endgroup$
    – Vogon Poet
    Mar 5, 2022 at 2:20

3 Answers 3

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Let us take an example from the early days of the space age: von Braun's bottle spacesuit.

von Braun's bottle spacesuit, original illustration

(illustration from 1954, uncertain origin and copyright status, but it appears everywhere)

Obviously, your peeps aren't operating in a vacuum or in microgravity, but the basic design is still one worth considering, because a one-person pressure hull intended for maintenance would be ideal for you needs.

The pilot could have unobstructed view above and all around them, and downwards to a certain degree. The insulated pressure hull they're standing in protects them from the environment. The remote manipulators on the outside of the hull might be controlled via direct physical connection to the pilot's arms and hands, giving them a surprising degree of dexterity without the need for advanced robotics. Such devices were used back in the day for manipulating dangerously radioactive materials, so they had to be reasonably fit for purpose.

Here are some that were used to work on nuclear rocket components:

Remote manipulator arms

(image credit: National Park Service)

I would envisage something tethered on a crane, either fixed to the hangar or maybe even from the top of the zeppelin's canopy. The tether provides a continuous source of cooling water to prevent the occupant getting baked, and a supply of air to stop them asphyxiating, much like the tethers used for commercial diving (though modern deep sea divers get warm water, of course).


But what if the remote manipulators were not enough?

Why, then you need a diving bell!

I found it weirdly difficult to get a decent picture or cross section of what I wanted, but I did discovered there was an olympic diver with the surname Bell. Just thought I'd share that.

The advantage of working under considerable pressure is that you can use that pressure to help form a seal. Your maintenance bells (again, tethered and held by a crane) have two chambers, a human-friendly chamber and an open end. The open end is manoevered against the damaged area of the airship canopy, and its pressure is reduced to minimally human-friendly levels. This causes it to suction on to the canopy. The inner section has a pressure door that is then opened to allow the occupant to perform fine manual work.

Obviously this is limited to the area covered by the open end of the bell, but large scale work can be done by the bottle suits above.

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  • $\begingroup$ A couple minutes after I wrote this I thought about thermal expansion and contraction stresses every time you take several hundred tons of metal across a 380C gradient. How long will it be before it is workable without a suit anyway? $\endgroup$
    – Vogon Poet
    Mar 6, 2022 at 14:18
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I'm going to go with "an ounce of prevention is worth a pound of cure". Any shot that cuts through the pressure hull is going to let hot, high pressure gases from outside rush into the gas envelop and crew gondola. The hulls are coated with something like aerogel as a thermal insulator so the simplest solution is to have that insulation inside the hardened pressure hull and it foam up when exposed to some constituent of the external atmosphere. The foam will then block the hole and harden off. That way in the event of a breach the insulation seals the hull temporarily and prevents the lose of habitability of the ship as a whole while it makes its way to safe harbour. There are many examples of such materials in modern glues, expanding foam insulation, etc... Better still if the insulation changes colour when it expands to fill a hole such that breaches are extremely visible to repair crews.

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Venetian blind patches.

patches

Figure 1: Your airship has a bunch of rolls of repair material. I think something like aluminum sheets could work. They are stored on one end of the ship exterior.

Figure 2: Holes are shot in the ship. Rolls corresponding to the strip on the ship are unrolled. The pull cords to unroll them are on the exterior of the ship and they can be unrolled from the interior.

Figure 3. Unrolled patch covers hole. It is held in place by the pressure differential. Maybe the crew applies glue.

Figure 4. If a patch is itself holed then next roll down is deployed to cover that.

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  • $\begingroup$ I think you need the patches to be on the inside. I don't think the people the OP is describing have the ability to make zeppelins with lower internal pressure than the air around them. The lifting gas might be breatheable, but even if it weren't zeppelins tended to have the lifting gas confined in balloons inside the outer envelope so people could work inside to apply patches. $\endgroup$ Mar 6, 2022 at 10:11
  • $\begingroup$ @StarfishPrime These are zeppelins? I thought they were more like submarines with huge pressure and temperature outside, less inside. In the OP it says "for a hangar" and I took hangar to mean some controlled environment where they park the ships for repair. If it is higher pressure inside you could go up to the inside part of the hole with a big square patch covered with glue and stick it on. The interior pressure will hold it. $\endgroup$
    – Willk
    Mar 6, 2022 at 15:25
  • $\begingroup$ For some reason the OP didn't mention that explicitly in this question (other than the airships tag), but all the linked questions mention it. Not your fault for missing it, certainly. $\endgroup$ Mar 6, 2022 at 15:29
  • $\begingroup$ @VogonPoet - this risks getting moved to chat. I think either you have the pressure differential and structural augmentations because you want the interior livable (like a submarine) or you have the pressure the same in and out and save the weight of the structural augmentations (like a zeppelin). The idea of the venetian blinds is to avoid the need for repair crew to physically go near the hole, inside or out. $\endgroup$
    – Willk
    Mar 6, 2022 at 16:29
  • $\begingroup$ @Willk A variation on this theme would definitely work. Likely not fully automated, and maybe not even rolled out (cableways and tracks can be just as easily damaged as the hull). I can see a low-tech version having patchwork sheets strategically dangling off the netting and some "difficult" crewmembers might be doing some climbing. Often it's more economical to just steal another ship, but when pressed with war... $\endgroup$
    – Vogon Poet
    Mar 6, 2022 at 16:52

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