Could a giant floating self-supporting city survive a thousand year voyage?

Question

One of the main plots in my world is that a huge ship arrives in a strange group of isles. This ship a gigantic city that completely self-supports itself with farms, houses, gardens, parks, and even recreational facilities. It has a population of 10,000 people called the Explods. There is even a government and class-system on the ship. The most interesting thing is, the ship has been going on a non-stop voyage for more than 1,000 years. This means that it has not stopped at any ports, seen any other ships, or had contact with outside civilization.

Is this plausible? What do the conditions of the voyage for this to possibly be able to happen? Would there have to be multiple ships? If this is not possible, then please tell me how it could change to be possible.

Also, there are no wars on this ship, and the people are fairly like-minded. The reason why the ship even exists is because of a legend of treasure at the end of a giant ocean. A small group of people who went on this journey built a huge ship in order to try to survive this journey. Over time this ship was expanded by the descendants in order help sustain the huge growing population.

Edit: This ship is not a very modern ship and the people who built it do not have access to steel and extremely durable substances.

This ship is in the water.

This world is not at all like Earth and has an almost unimaginably big ocean with nothing in it except for sea creatures, and this ocean separates two major landmasses.

Answer 1

I don't think this is actual plausible from the boat side of things. Its not built using steel or a super durable material. Boats are usually built with a backbone (the keel) and this can't be replaced as it forms the foundation of the boat.

Secondly, the reason wooden boats had a maximum size wasn't because they didn't try to built it any bigger. They did, and it failed miserably. Large ships have huge problems traversing across waves and stormy weather and these forces will tear a very large ship apart if it isn't made out of a super durable material.

You said the ship was expanded to account for the growing population. This fundamentally means you need more land, more building materials to get more houses and expand the boat. This would be incredibly hard to do. How would you get all the extra material? where do you grow it? How do you get more building material? Your not just recycling, your generating extra materials on a ship without every contacting an outside civilization. Your also expanding the ship while its still working and not going to port. In addition, eventually, overtime the keel of the ship will wear out and you can't exactly replace it without taking apart the ship.

You also have a problem with all the salt water. Where do you get fresh water from? Evaporation is a terribly slow technique to extract water, and a fire to catch water vapors requires a huge amount of fuel to keep running. You would also have the ocean spraying salt water over your ship, especially in stormy weather and when it gets hit by waves. Your farm lands would need to be exposed to sunlight and salt will eventually leak into it.

You would also be unable to simply have all the resources you need on the ship without pretty advanced technology. Your not going to get parks, gardens and recreational areas into small ships and large ships won't survive the ocean. You would also need support faculties to collect and recycle garbage, create tools and medical equipment.

The problem I see, is that this is a sea faring ship, and you seem to want a lower level of technology. Even at our technology level, there is no way to have a ship that can support an entire civilizations while never interacting with an outside civilization.

Answer 2

I see a some issues here:

The maintenance of a ship is not negligible, especially in water and without advanded technology to build it. On earth, non-steel ship were made of wood. And sea lifeforms can severely damage wood over time. You usually have to repair holes, change some parts, and this is usually done by taking the ship out of the water. Doing this on a gigantic moving ship seems quite impossible without some handwaving here (magic, unknown material...)

The size of the ship is significant. Low estimates of the area needed to feed an adult with a 2300 cal vegetarian diet are 0.44 acres (total 4400). Medieveal urban density is about 60 people per acre, so this would be small (170 acres) compared to the food area. So food production and houses for 10.000 people would require 18.5 sq. km (4.3 x 4.3 km). This is not completely unrealistic, but it cannot be a classical ship: sea faring would break the structure. It would be loosely coupled parts bound together, a kind of floating city and gardens. Such structures exist, including floating gardens, for example on the Inle Lake. But lakes have less constraints that seafaring: even modern ships can be broken or severely damaged by wave. A floating city would be at great risk. And once your gardens are full of salty water, no more tomatoes.

First conclusion is that it is unrealistic: unsustainable, engineering nightmare, fragility. Not sure how you can fix this without some special material here...

Answer 3

Depending on the size of the city ship I don't see a reason why it couldn't survive. The bigger the better because it allows room for farms, and machinery that would clean its air and repurpose waste, and create/store fuel (nuclear minimum?). They could mine metals from asteroids from time to time to repair mechanical things and refurbish the hull and "grow" the ship.

I'm more concerned with the number you have for the people. 10,000 doesn't seem like enough without things getting... unsavory. 100,000 might be better. Someone else might be able to give you a better answer as to what is a good minimum number for how many people you would need to keep a stable society without going extinct or having inbreeding issues. Either way you're going to want as diverse a gene pool as possible too.

EDIT: Apologies! My answer was about a SPACE ship. LOL! I was deep in sci-fi mode!

Answer 4

1000 years is a long time to have not found land. Were they actively trying to avoid any landfall?

Things drifting in the ocean often make it to the other side of the world in a couple of years. Something travelling at 0.1 km/h (less than most ocean currents) would travel about 876000 km in 1000 years. that's about 21 times around the world.

It's possible that they were trapped in some sort of mid-ocean gyre but none on earth are stable enough to hold something for 1000 years.