A Self-Sufficient Seafaring Society

[Ormurinn]

With Added Alliterative Appeal

Eala

I've recently been thinking about this concept, which came originally from a Nationstates nation I founded, and now I'm wondering about the feasibility of it. I know ships like this are capable of desalinating their own water using electricity they generate, but would there be enough space to grow the required food? Would Nuclear power be essential, or would you be able to get by on solar energy? What about algae-derived biofuel? Bear in mind that it has to be a self-sufficient community, it can't be reliant on fuel from landlubbers!

Im aware that ships tend to need hull treatments every so often to remain seaworthy, is there any modern technology that could ameliorate this? How easy would it be to rely on aquaculture - perhaps dragging nets full of farmed fish behing the vessels, or using shallow basins full of algae to create food supplies? Is some sort of migratory lifestyle based on following herds of whales possible? What about the inevitable psycological effects? Finally, I suppose, what would it cost?

As you can probably tell, I have no idea about almost any of this - but I'm guessing theres some experts on here. So heres the proof-of-concept challenge. The small, Northumbrian town of Berwick-upon tweed has, due constant debate over whether it should be part of Scotland or England, has decided to secede from both. Having no legal right to the land it's established upon, the town has determined to take to the sea, with all it's 11,665 inhabitants. Parliament undertakes to underwrite all costs. The challenge for you, the xkcd community is to answer this:

1) Is this even possible?

2)What would be required?

3)Can you make it cost less than the U.K government has given so far to failed banks? (£325bn)

4) If 3) is trivial, how great a population can we make permanent seafarers with that much money?

[skippysheila]

Point of order:

Can you make it cost less than the U.K government has given so far to failed banks? (£325bn)

The UK government has not "given" this money to banks. The Bank of England has used this amount of money to buy assets from the banks to increase the liquidity of their balance sheets. All the things they've bought can and will be sold again later. They have bought (mostly) gilts, not stuffed fivers in the pockets of bankers. The link does not say that this money has been given to the banks, it gives the size of the quantitative easing program i.e.: the amount of money that has been used to purchase gilts and other relatively secure assets.

If you're thinking of the amount of money owed by the banks to the government, it was around £450bn in September 2011 (the last time I can reliably remember a figure). Given that it was over £1trillion at its worst, I think it's fair to assume that this is being paid back and is not a gift.

The situation is fucked enough anyway without making shit up.

Edit: tpyos

[Dr. Diaphanous]

Unless the people are going to want to eat just fish, you are going to need to grow crops and trade for food.

Growing crops

The minimum amount of agricultural land necessary for sustainable food security, with a diversified diet similar to those of North America and Western Europe (hence including meat), is 0.5 of a hectare per person. This does not allow for any land degradation such as soil erosion, and it assumes adequate water supplies. Very few populous countries have more than an average of 0.25 of a hectare. It is realistic to suppose that the absolute minimum of arable land to support one person is a mere 0.07 of a hectare–and this assumes a largely vegetarian diet, no land degradation or water shortages, virtually no post-harvest waste, and farmers who know precisely when and how to plant, fertilize, irrigate, etc.

(1 hectare = 2.47 acres = 10 000m²)

The longest ship ever built is the Seawise Giant oil tanker. 458.45m long x 68.8m wide = 3.15 hectares surface area (Actually less as she is not a perfect rectangle).
That's a maximum of 45 people on an intensively-farmed vegan ship covered in crops (assuming they are not damaged by salt water, which they are).

I guess you could fill the lower decks with hydroponics but you still aren't going to be self sufficient with food.

To buy food you need an economy. You could probably make a few bucks as a tax haven, but that would make you unpopular? Tourism maybe. But anything requiring space is going to be severely limited.

[Ormurinn]

Unless the people are going to want to eat just fish, you are going to need to grow crops and trade for food.

Growing crops

The minimum amount of agricultural land necessary for sustainable food security, with a diversified diet similar to those of North America and Western Europe (hence including meat), is 0.5 of a hectare per person. This does not allow for any land degradation such as soil erosion, and it assumes adequate water supplies. Very few populous countries have more than an average of 0.25 of a hectare. It is realistic to suppose that the absolute minimum of arable land to support one person is a mere 0.07 of a hectare–and this assumes a largely vegetarian diet, no land degradation or water shortages, virtually no post-harvest waste, and farmers who know precisely when and how to plant, fertilize, irrigate, etc.

(1 hectare = 2.47 acres = 10 000m²)

The longest ship ever built is the Seawise Giant oil tanker. 458.45m long x 68.8m wide = 3.15 hectares surface area (Actually less as she is not a perfect rectangle).
That's a maximum of 45 people on an intensively-farmed vegan ship covered in crops (assuming they are not damaged by salt water, which they are).

I guess you could fill the lower decks with hydroponics but you still aren't going to be self sufficient with food.

To buy food you need an economy. You could probably make a few bucks as a tax haven, but that would make you unpopular? Tourism maybe. But anything requiring space is going to be severely limited.

I'd assume plants would be watered with water from the ships desalination plant, but that is rather less crop-growing capacity than I had hoped. Assuming some of the crew's calorific needs was supplied by fish we might be able to push it a bit higher, but it's not good news at all. You'd definately need hydroponic farmships with artificial lighting. Raising cattle is definately out.

Might it be possible to maximise insolation with purpose-built towed greenhouses? Something like a high-tech version of these? They'd be impossible to get through rough seas though. Maybe tow them out to an area of calm waters, anchor them, plant slow-growing but high yield crops and return for them after the growing season? Assuming an annual migration, that'd probably require splitting into smaller fleets that each leave a farm for the next one in the chain.

Crop yields from some species of blue-green algae are enormous, and it's nutritious, but then it's disgusting green goop.

Anyone have any thoughts on power generation?

Economically, is there some kind of large, bulky, non-time-intensive good that needs regularly shipping in a predictable pattern? With enough ships to carry an entire town you're looking at a lot of hauling capacity - maybe that'd be an option.

[Dr. Diaphanous]

Anyone have any thoughts on power generation?

Looking at Seawise Giant again, it had 50,000 HP engines. 50 000 HP = 37 MW. On a bright clear day the best solar irradiance you can hope for is 1,000 W/m². So if the engines are running at full power on a bright day you need 37 000 m² of 100% efficient solar panels or 176 190 m² of 21% efficient panels (which is probably still unrealistically good). 17.6 hectares is impossible for our ship unless I've done my maths wrong.

Nuclear would be by far the most convenient option if you want to be moving regularly and not constantly refueling. But this would pose extreme political problems, even if you had the expertise to build it.

Economically, is there some kind of large, bulky, non-time-intensive good that needs regularly shipping in a predictable pattern? With enough ships to carry an entire town you're looking at a lot of hauling capacity - maybe that'd be an option.

Hows about Slavery? As a bonus you could recruit the strongest slaves and feast on the weakest.

[Adacore]

Unless the people are going to want to eat just fish, you are going to need to grow crops and trade for food.

Mostly just an aside, since you're almost certainly going to want grains and things, but you shouldn't neglect seaweed (or, as Ormurinn suggests, algae). It's not popular in the west, but seaweed is a major component of a lot of east Asian cuisines, and is a reliable source of edible vegetable matter from the sea, with decent nutritional value.

[Enokh]

Considering you started off your post with a link to tvtropes, I'm surprised anyone responded within 24 hours of the topic being made.

[Fantastic Idea]

I've never been able to get into TV Tropes.
Seriously.

But I am wicked into seafaring!

I don't know the answers to all the questions, but I do know what we call 'an area of calm waters' on which you could put a greenhouse boat, and that is 'a lake'. The Sargasso Sea might be worth a look, because it is in the doldrums, but even then you would have to make something very durable and able to be anchored in miles deep water. In most areas it isn't remotely feasible to put what we'd generally consider a greenhouse on the water. However I have seen some absolutely killer awesome greenhouse/water purification ideas that might make a difference.
Like this: http://inhabitat.com/bubble-shaped-skys ... r-factory/
*probably my favorite idea I found on the internet ever
and while making a 'skyscraper' migh tnot be feasible on a ship, making one that progresses through the decks of the ships would make sense and if they were still round, the water would be able to move with the rocking of the ship and not be damaged. This is easily something that could be built into say, a cruise-ship sized vessel.
This design is also supposed to run on tidal power, but I think we should be considering creating something simply powered by the rocking a boat takes on the waves. It's like tidal power, but say you just hang some bits off the sides or aft and the swells will move it around and it will generate power, but someone with better engineering knowhow can shoot that down or work it out.
Having discussed living on a boat more than once, I've gone into the idea of using wind power on a boat. There is very seldom no wind on the sea. There's the doldrums, and to get through that in a ship that didn't run on gas your only option would be the sun. It would be best to have systems to harness all three of these energy sources, Wind, Solar and Tidal. If we were trying to grow crops alongside or on top of the sargassum, we'd need the ability of the solar energy to bring us in and out of those areas of low wind and small swells.

I don't know that there is any way to feed an entire society while remaining on the ocean, but as previous posters have noted you have to take into account the availability of seaweed and the place it already has in many diets around the world. It is also a super easy thing to grow in the sea, takes almost no energy to cultivate and is simple to harvest. Seaweed, like oysters and mussels and such, need only the ocean water around them (in a relatively clean state).

Aquaculture between ships or in nets makes very, very little sense. BUT. Have you seen Waterworld?
It's a terrible movie in terms of the attachment to reality and physics and sustaining life, but they've got some neat builds. If there were an artificial Atoll like in this movie, but the center was lined with metal bars, like a giant sieve, it would be possible to farm some ocean fish. Most ocean fish, however, are built to swim far and wide, and don't take to being held in one place. Tuna alone swim hundreds of miles across the ocean each year, and would not be possible to farm. It might be worth having a central atoll near or in the Sargasso Sea and have smaller nomadic fleets that travel after schools of tuna, or bass, or sharks or sea turtles.
I don't believe that in the current state of the oceans, following whale pods would keep any society fed.
Some aquatic mammals would have to be on the menu, like seal and sea lion, because fish frequently don't have enough fat to keep humans happy all the time.

I think this could be possible. I couldn't remotely begin to wrap my brain around a dollar amount. I am not even sure which technologies would be feasible. But I think it's possible. And if it is, I want to live there.

[Izawwlgood]

Out of curiosity, why are people assuming a single boat for the surface area? Why wouldn't setting up a number of floating platforms, Mayan (Inca? Aztec? I can never recall) style be the way to go? Your sea faring society doesn't have to be limited to a single boat.

Didn't any of you read Snow Crash?

[eSOANEM]

Out of curiosity, why are people assuming a single boat for the surface area? Why wouldn't setting up a number of floating platforms, Mayan (Inca? Aztec? I can never recall) style be the way to go? Your sea faring society doesn't have to be limited to a single boat.

I was thinking just this.

That said, a single enormous floating platform would definitely be better than multiple ones due to stability considerations. In general, the height of a wave needed to capsize a craft goes with the square root of the distance across the craft perpendicular to the wavefront. Clearly then, larger platforms will be less likely to capsize. Furthermore, a large platform will straddle several waves and so reduce the rocking due to them.

So, for Berwick-on-Tweed-on-Sea, going with the estimate of half a hectare per person we'd need a 5832.5 hectare platform (plus living space) which means that, assuming a circular platform (because symmetry), you'd need it to be ~ 9km in diameter. Going with the 0.07 hectares (and therefore the vegetarian diet), it'd still need to be ~3.5km in diameter.

Still, a single rigid platform that large, whilst extraordinarily expensive (and so, probably blowing the £450 billion budget), would comfortably straddle a very large number of waves even in the roughest seas so would be extremely stable. In fact, I suspect that it would be so stable that it would be easy for someone in the centre to forget they were at sea.

[wam]

Ah but when you start getting large you get a different issue with waves. In that in big seas, you can end up with both ends on a wave and middle upsuported which then puts a large strain through the structure.

I reckon the best system would be a series of smaller floating platforms linked with a semi rigid system, that would allow some movement but keep everything together.

[Dr. Diaphanous]

But if you're going for something that big, it won't be very mobile. And if it's not mobile, why not just use an island? Or make an island by dumping rock into a shallow sea.

[Fantastic Idea]

Out of curiosity, why are people assuming a single boat for the surface area? Why wouldn't setting up a number of floating platforms, Mayan (Inca? Aztec? I can never recall) style be the way to go? Your sea faring society doesn't have to be limited to a single boat.

Didn't any of you read Snow Crash?

I didn't read Snow Crash but i did suggest that there be one or more stationary atolls with associated hunting fleets.
Hunt AND Gather!

Ah but when you start getting large you get a different issue with waves. In that in big seas, you can end up with both ends on a wave and middle upsuported which then puts a large strain through the structure.

I reckon the best system would be a series of smaller floating platforms linked with a semi rigid system, that would allow some movement but keep everything together.

I don't think you're nevessarily right here. oil drilling rigs are giant things but are actually floating, as stable as they are. if the platform lies low enough in the water, there is no pressure differential when waves move across, and no unsupported weight, but it may have to be tethered to the bottom like an oil rig.

But if you're going for something that big, it won't be very mobile. And if it's not mobile, why not just use an island? Or make an island by dumping rock into a shallow sea.

But in this narrative, the islands are all taken' and the materials for building a fleet would be cheaper than the materials for building an island.Anyway who builds an island in a time of sea level rise? only the silliest of gods.

[Ormurinn]

But if you're going for something that big, it won't be very mobile. And if it's not mobile, why not just use an island? Or make an island by dumping rock into a shallow sea.

Most shallow waters tend to be in the territorial waters of a nation though. Does anyone have a reliable source for the calorific load that a fishing ship can provide in different fishing grounds? Or even how much of your diet can be made up of fish before people need vegetables? Don't the inuit pretty much just eat marine mammals and fish?

Likely to be a completely ridiculous idea, but what about the marine equivalent of nomadic pastoralism? Would it be possible to train/domesticate whales or dolphins to follow the fleet, and live in part off their meat and milk? Could you could use ultrasound-emitter equipped schooners to herd them like sheep?

Finally, what about the feasibility of wind power for propulsion? Im now envisaging an annual migration of a huge flotilla following the clipper route, pods of whales in tow, dragging huge green biodomes full of seaweed and spiranella in their wake. This is a nice image, even though I'm sure it's implausible

[eSOANEM]

Ah but when you start getting large you get a different issue with waves. In that in big seas, you can end up with both ends on a wave and middle upsuported which then puts a large strain through the structure.

I reckon the best system would be a series of smaller floating platforms linked with a semi rigid system, that would allow some movement but keep everything together.

Obviously the structure needs to be rigid enough to take the strain of one full wavelength (which in high seas can be quite large) unsupported however this would be fairly easy given the many very rigid materials available nowadays (I'm looking at you reinforced concrete).

Furthermore, if the platform sits sufficiently low in the water, the space between two waves' peaks will not be completely unsupported and the strain will be reduced.

Additionally, in order to get the stability of a large platform, you need to be able to straddle several waves. If you can do this, you end up with the bits over the trough being less supported than those over the peaks and so you'll get stresses introduced. Furthermore, you'll get these stresses if you're anything over one wavelength across but you'd only get increased stability if you're over a fairly large number of wavelengths.

Therefore, if you want to introduce smaller platforms in order to reduce this stress you'll lose the main stability benefits (as the platforms will still rock and rise and fall with the waves). If you're doing this, there's little reason to connect the platforms at all and you might as well just stick outriggers on all your boats (which will reduce the risk of capsize but not rocking or rising and falling).

But if you're going for something that big, it won't be very mobile. And if it's not mobile, why not just use an island? Or make an island by dumping rock into a shallow sea.

Well if you want to be self-sufficient that's how big it needs to be. The question is just whether you have all joined up or in lots of bits.

And a single enormous circle could be very mobile, it's simply a question of how much engine power you give it. In fact, if you take a large fleet of displacement vessels (all going at the same speed) and try to race it over a long distance against the same mass arranged as a single rigid circle with the same total engine power, the circle will do better as it will have significantly less wetted area (the main cause of drag on a boat). The wetted area can then be reduced further by changing the shape away from a circle (that was mainly chosen because it gave an idea as to the scale of something big enough to sustain Berwick-on-Tweed-on-Sea) towards a more conventional boat shape.

There's a general rule that a displacement vessel's top speed is proportional to the square root of its length (IIRC it assumes a constant power/weight ratio or something like that) so a bigger boat should certainly be able to go faster (and with the same power to weight ratio should not accelerate much slower) than a collection of smaller boats.

But if you're going for something that big, it won't be very mobile. And if it's not mobile, why not just use an island? Or make an island by dumping rock into a shallow sea.

But in this narrative, the islands are all taken' and the materials for building a fleet would be cheaper than the materials for building an island.Anyway who builds an island in a time of sea level rise? only the silliest of gods.

Iceland and Hawaii.

But then, they don't have much say in the matter.

Finally, what about the feasibility of wind power for propulsion? Im now envisaging an annual migration of a huge flotilla following the clipper route, pods of whales in tow, dragging huge green biodomes full of seaweed and spiranella in their wake. This is a nice image, even though I'm sure it's implausible

Sails would certainly be a good way to get some of the propulsion for whatever sort of vessel(s) we have however towing anything as a sailing boat is a bad idea.

The maximum amount of power you can get from a sailing boat depends upon its stability (because eventually it'll just get blown over) and as soon as you start towing things astern, you add significant amounts of weight without adding any more stability. Because of this, your power to weight ratio falls off a cliff. You'd be better off having sails on each craft separately.

[Fantastic Idea]

But if you're going for something that big, it won't be very mobile. And if it's not mobile, why not just use an island? Or make an island by dumping rock into a shallow sea.

Most shallow waters tend to be in the territorial waters of a nation though. Does anyone have a reliable source for the calorific load that a fishing ship can provide in different fishing grounds? Or even how much of your diet can be made up of fish before people need vegetables? Don't the inuit pretty much just eat marine mammals and fish?

Likely to be a completely ridiculous idea, but what about the marine equivalent of nomadic pastoralism? Would it be possible to train/domesticate whales or dolphins to follow the fleet, and live in part off their meat and milk? Could you could use ultrasound-emitter equipped schooners to herd them like sheep?

Finally, what about the feasibility of wind power for propulsion? Im now envisaging an annual migration of a huge flotilla following the clipper route, pods of whales in tow, dragging huge green biodomes full of seaweed and spiranella in their wake. This is a nice image, even though I'm sure it's implausible

The caloric load of a fishing ground depends on the fish, with things like tuna having more meat and fat than a bass, but traveling farther and maybe being harder to catch.
I am pretty sure that the current arctic inhabitants do eat more than meat and fish, because it's 2012 ffs, but it's been a while since i took that class. i think that you would want to do the most to make large fish half of the biomass of the diet or less, to prevent poisoning via toxin biomagnification.
and yes, the whale herding idea is completely ridiculous. again, it's 2012 and we don't even know why they beach sometimes, let alone how to get them to do what we want. they probably mostly hate us, but that bit's just meauxtheory, and trying to harvest milk from a whale is probably going to be a one-way trip of an errand.
Humpbacks and some other whales will be unafraid enough to hang about but they won't follow a ship around.
Fish, however, will.
Sharks will follow any ship that's got food particles getting into the water, and anything that remains relatively stationary, maybe has tethers to the bottom or has dangling ropes/chains/keels, will become a Fish Aggregating Device.
That,s why governments can dump and old bridge in the ocean and call it 'reef creation'. Fish like stuff to hang about and hide in.
The wind power propulsion idea is cool, but as i said above you need a back up power supply and also, why make biodomes of things that grow in the ocean? it would make more sense to have them grow non-aquatic plant life, maybe?

[Izawwlgood]

We're assuming pretty advanced technology but treating our agriculture platforms as though they're just sheets of buoyant material with dirt ontop. People! We are masters and engineers of this system;
Multiple smaller atolls that can seal off and submerge. 'Bad weather tipping' problem solved. In fact, just do that for everything. The notion that we need to make our entire society dependent upon a single supervessel for both living space and surface area is sort of silly. Big waves? Just dive until things clear up.

[natraj]

i'd go live in armada if it were established. clearly the primary occupation of this floating city needs to be piracy.

[Ormurinn]

i'd go live in armada if it were established. clearly the primary occupation of this floating city needs to be piracy.

I like the idea thematically, but any world where several landed states maintain blue-water navies and cruise missiles is going to make that sort of thing impossible.

[eSOANEM]

We're assuming pretty advanced technology but treating our agriculture platforms as though they're just sheets of buoyant material with dirt ontop. People! We are masters and engineers of this system;
Multiple smaller atolls that can seal off and submerge. 'Bad weather tipping' problem solved. In fact, just do that for everything. The notion that we need to make our entire society dependent upon a single supervessel for both living space and surface area is sort of silly. Big waves? Just dive until things clear up.

This will limit the sea areas you can live in. In order for the plants to grow and the agriculture to function you need sunlight which limits the amount of time you can spend below, this puts a limit on the proportion of the time it can be stormy somewhere where you want to stick Berwick-on-Tweed-on-Sea and so would rule out the whole Southern Ocean (because that's a constant storm) and probably also most other large seas.

Sharks will follow any ship that's got food particles getting into the water, and anything that remains relatively stationary, maybe has tethers to the bottom or has dangling ropes/chains/keels, will become a Fish Aggregating Device.

Yup, no need to even be trailing much gear, there are accounts of people whose yachts went down catching enough fish to survive, and all those rafts trail is a single drogue which would be a reasonable distance from the raft.

[Dr. Diaphanous]

What about being on the bottom of the sea? An underwater city, with huge gills to harvest oxygen from the water. Huge vehicles drive along the sea bed to mine and to steal fuel from oil wells. Submarines criss-cross the ocean between other undersea colonies.

This has the advantage that land nations would find it hard to attack to even find you, as even their submarines are really dedicated to surface warfare. Also, they wouldn't believe you existed as the idea is impossible (impossible = some of the engineering would be quite tricky).

[Ormurinn]

What about being on the bottom of the sea? An underwater city, with huge gills to harvest oxygen from the water. Huge vehicles drive along the sea bed to mine and to steal fuel from oil wells. Submarines criss-cross the ocean between other undersea colonies.

This has the advantage that land nations would find it hard to attack to even find you, as even their submarines are really dedicated to surface warfare. Also, they wouldn't believe you existed as the idea is impossible (impossible = some of the engineering would be quite tricky).

"My name is Andrew Ryan, and I'm here to ask you a simple question..."

[Izawwlgood]

n order for the plants to grow and the agriculture to function you need sunlight which limits the amount of time you can spend below

I think you're underestimating the amount of light present 20-30 ft under. It's less, surely, but most of whats filtered out with any sort of depth is the red light. So your plants don't flower as effectively; hardly an issue in the short term. And assuming the center of our floating city is a giant nuclear power plant, it's not like electricity is going to be in particularly short supply; just supplement submerged hydroponics chambers with a bit of blue and red light.

Lash a bunch of these together, and tether them to a couple underwater jets aimed against the tide; they'll fan out instead of glomming or slamming into one another. Or if you're in shallow enough territory, just anchor them.

[eSOANEM]

What about being on the bottom of the sea? An underwater city, with huge gills to harvest oxygen from the water. Huge vehicles drive along the sea bed to mine and to steal fuel from oil wells. Submarines criss-cross the ocean between other undersea colonies.

This has the advantage that land nations would find it hard to attack to even find you, as even their submarines are really dedicated to surface warfare. Also, they wouldn't believe you existed as the idea is impossible (impossible = some of the engineering would be quite tricky).

Natural-ish agriculture would be impossible. Hydroponics labs could work though.

n order for the plants to grow and the agriculture to function you need sunlight which limits the amount of time you can spend below

I think you're underestimating the amount of light present 20-30 ft under. It's less, surely, but most of whats filtered out with any sort of depth is the red light. So your plants don't flower as effectively; hardly an issue in the short term. And assuming the center of our floating city is a giant nuclear power plant, it's not like electricity is going to be in particularly short supply; just supplement submerged hydroponics chambers with a bit of blue and red light.

dI/dx=-cI (where I is the intensity) [citation]

looking at this chart the absorption coefficient for visible light in pure sea-water is between 10^-2cm^-1 and 10^0cm^-1 depending on wavelength, but for yellow light, is at about 10^-1cm^-1.

Therefore:

dI/dx=-I/10

so I=I₀e^(-x/10) which means that at 10m (1000cm), I=I₀e^-100 and so the intensity of yellow light has dropped by a factor of ~10^-13 (and the other colours will be attentuated by a factor between ~5*10^-5 and ~5*e^-435).

So you'll have trouble farming crops at any reasonable depth using sunlight (the formula also shows that at just 7cm of depth, half the yellow light will have been attenuated and that, after half a metre of sea water, less than 1% of yellow light from the surface wil lremain).

So yeah, hydroponics would be essential for all the light to the plants (not that this should be a problem with sufficient nuclear power).

Lash a bunch of these together, and tether them to a couple underwater jets aimed against the tide; they'll fan out instead of glomming or slamming into one another. Or if you're in shallow enough territory, just anchor them.

It's not the tide which would bash them together, it's their wake. As long as they drift, they'd be perfectly fine sitting near each other, but as soon as you get any speed up, the wash will start trying to pull the rafts together.

Of course, this isn't a problem if you're submerged, but then you've got other problems (like agriculture with natural light).

[Soralin]

Obviously the structure needs to be rigid enough to take the strain of one full wavelength (which in high seas can be quite large) unsupported however this would be fairly easy given the many very rigid materials available nowadays (I'm looking at you reinforced concrete).

Furthermore, if the platform sits sufficiently low in the water, the space between two waves' peaks will not be completely unsupported and the strain will be reduced.

Additionally, in order to get the stability of a large platform, you need to be able to straddle several waves. If you can do this, you end up with the bits over the trough being less supported than those over the peaks and so you'll get stresses introduced. Furthermore, you'll get these stresses if you're anything over one wavelength across but you'd only get increased stability if you're over a fairly large number of wavelengths.

Something like some big massive bowl perhaps. You could have a big plain of farmland, with 20m+ tall walls on the sides or such, where the base of it is actually below sea level. You could make it big enough that waves would end up acting a bit differently, the crests of waves wouldn't go over the top, and the troughs of waves wouldn't go underneath, and it wouldn't move much with them, since it would only be an edge effect.

Long term self-sufficiency takes more than food and water and air and such though, you also have to be able to repair or replace any machines that you're using, which takes raw materials. I suppose you can filter raw materials out of seawater. If you have a fission reactor, it's possible to filter uranium out of the trace amounts in seawater, and get net positive energy out of the whole process: http://en.wikipedia.org/wiki/Uranium_mi ... m_seawater . You could get a bunch of other materials in the same way, although it might take a long time to get enough resources for replication, to, say, build a completely new additional ship (Which you would essentially need to be able to do, if we're taking self-sufficiency to it's extreme). But I suppose you could get raw material from elsewhere too, like the seafloor, or simply from land, if you're not trying to be that self-sufficient.

For extra challenge, what about a self-sufficient skyfaring society?

http://en.wikipedia.org/wiki/Cloud_nine ... _sphere%29
http://en.wikipedia.org/wiki/Colonizati ... ing_cities

[Izawwlgood]

So you'll have trouble farming crops at any reasonable depth using sunlight (the formula also shows that at just 7cm of depth, half the yellow light will have been attenuated and that, after half a metre of sea water, less than 1% of yellow light from the surface wil lremain).

Plants don't use yellow light for photosynthesis. They use orange/red, and blue/violet. Here:
http://www.emc.maricopa.edu/faculty/far ... ookps.html

Also, plenty of photosynthetic organisms live up to 50m underwater. Light often isn't the limiting factor in plant growth, CO2 is.

[Fantastic Idea]

What about being on the bottom of the sea? An underwater city, with huge gills to harvest oxygen from the water. Huge vehicles drive along the sea bed to mine and to steal fuel from oil wells. Submarines criss-cross the ocean between other undersea colonies.

This has the advantage that land nations would find it hard to attack to even find you, as even their submarines are really dedicated to surface warfare. Also, they wouldn't believe you existed as the idea is impossible (impossible = some of the engineering would be quite tricky).

Natural-ish agriculture would be impossible. Hydroponics labs could work though.

n order for the plants to grow and the agriculture to function you need sunlight which limits the amount of time you can spend below

I think you're underestimating the amount of light present 20-30 ft under. It's less, surely, but most of whats filtered out with any sort of depth is the red light. So your plants don't flower as effectively; hardly an issue in the short term. And assuming the center of our floating city is a giant nuclear power plant, it's not like electricity is going to be in particularly short supply; just supplement submerged hydroponics chambers with a bit of blue and red light.

dI/dx=-cI (where I is the intensity) [citation]

looking at this chart the absorption coefficient for visible light in pure sea-water is between 10^-2cm^-1 and 10^0cm^-1 depending on wavelength, but for yellow light, is at about 10^-1cm^-1.

Therefore:

dI/dx=-I/10

so I=I₀e^(-x/10) which means that at 10m (1000cm), I=I₀e^-100 and so the intensity of yellow light has dropped by a factor of ~10^-13 (and the other colours will be attentuated by a factor between ~5*10^-5 and ~5*e^-435).

So you'll have trouble farming crops at any reasonable depth using sunlight (the formula also shows that at just 7cm of depth, half the yellow light will have been attenuated and that, after half a metre of sea water, less than 1% of yellow light from the surface wil lremain).

So yeah, hydroponics would be essential for all the light to the plants (not that this should be a problem with sufficient nuclear power).

Lash a bunch of these together, and tether them to a couple underwater jets aimed against the tide; they'll fan out instead of glomming or slamming into one another. Or if you're in shallow enough territory, just anchor them.

It's not the tide which would bash them together, it's their wake. As long as they drift, they'd be perfectly fine sitting near each other, but as soon as you get any speed up, the wash will start trying to pull the rafts together.

Of course, this isn't a problem if you're submerged, but then you've got other problems (like agriculture with natural light).

Another aspect of the light issue is that if you're in more fertile zones where plants and fish thrive the plankton and suspended particles in the water will make light even less available than it would be in 'pure' seawater as the above equation uses. Not to mention adding in a secondary artificial light source would be an unnecessary drain. I'm not sure if we are assuming some kind of nuclear powered city center while also making plans for a bunch of small atolls, do you want one or the other, Iz? I'm not getting a clear picture of what you're describing.

I would never advise a nuclear powered anything in this system because of the instability of the power source and the unpredictability of the oceans. I am not even a bit convinced humans currently have the technology to make a nuclear power system that could power a whole society and still be safe enough to actually warrant living there. I mean, nuclear submarines work but their lifespan is about 25 years and the nuclear fuel lasts that long in the new ones, earlier models have to refuel their rods. Creating a system on the water to do the nuclear material work on would be kind of freaking insane- a nuclear sub built in 2000ish cost $1.8 billion US. I see a much more reasonable proposal in wind or sun or tide power, things that can be built and maintained on the ocean.

[pyronius]

question: beyond the difficulties with repairs and getting it into port is there any particularly good reason most boats don't build "down"? it seems to me that the deeper your boat extends below the surface the more space you have to utilize as you please. I'm thinking you want to build both down and up. the lower decks below the surface would be cabins, nuclear power, and heartier plants or animals with the crop production portions closer to the top so that an amount of natural light could be let through using whatever particularly tough and transparent material was available which would of course be supplemented by specialized light bulbs. the portion above the surface would be many levels of indoor agricultural space built similarly to those below design focused on harnessing as much natural light as possible with areas around it set with mirrors to direct additional amounts of light up toward areas that needed it. basically a multi-story farm building. i think that if designed right and a large amount of otherwise unused space were devoted to hanging plants you could have a decent yield of fruits and vegetables. meat would be tricky but just go ask someone from peta for a brochure and you'll see how little space you can keep a pig or a chicken in if necessary. i'm imagining that this would be supplemented by smaller fishing vessels which would dock with the ship for the night and go out each day as some group's job.

As far as power goes i think you're really best off with nuclear. there's a reason militaries use it on large ships. you may or may not be able to find an alternative, but it would only be worth a look if your main concern was being eco friendly or if other governments didn't like the idea of you having nuclear tech.

If you did build down deep like i was saying then you do have the issue of not being able to bring it into port which mean that you would both have to use the smaller boats for trips anywhere near land and have to repair the boat at sea. frankly though, if you're trying to design a self sufficient sea faring micronation boat then being able to manage repairs at sea is something like priority number one on your list of things to learn how to do.

I would never advise a nuclear powered anything in this system because of the instability of the power source and the unpredictability of the oceans. I am not even a bit convinced humans currently have the technology to make a nuclear power system that could power a whole society and still be safe enough to actually warrant living there. I mean, nuclear submarines work but their lifespan is about 25 years and the nuclear fuel lasts that long in the new ones, earlier models have to refuel their rods. Creating a system on the water to do the nuclear material work on would be kind of freaking insane- a nuclear sub built in 2000ish cost $1.8 billion US. I see a much more reasonable proposal in wind or sun or tide power, things that can be built and maintained on the ocean.

I know a few guys in the nuclear industry (safety watchdogs of sorts) and what I've taken away from them is that nuclear power is vastly more safe than people make it out to be. Don't get me wrong, I personally don't know anything about it, but from what I've been told all the major nuclear disasters have either been extremely minor and blown out of proportion (three mile island) or entirely the product of human error and imbecilic failures (Chernobyl, Fukushima). for instance, on day one of Fukushima one of the guys was in the 100 or so people informed and asked to consult and his response was pretty much that there were things that could be done but that they should have seen this as a possibility for a long time and the japanese government had simply not bothered to properly prepare. in the days afterward i constantly saw him exasperated about the way japanese nuclear engineers had been trained. essentially they were the best people in the world to have so long as everything was working right but the second they encountered something that wasn't in the manual they had no creativity to solve it and thus things just went from bad to worse as they ran around like chickens with their heads cut off because somewhere down the line some official had said "yeah, an earthquake could kill us all, but who the fuck cares? what are the odds?". so pretty much you're good to go as long as you aren't cutting corners and can think on your feet instead of needing to be spoon fed instructions.

oh, fun fact: you can actually go swimming in nuclear reactors. so long as they're currently cool you won't be harmed if you stay far enough away from the material. there's an entire career based on doing repairs using scuba gear in active reactors. i have to imagine its awesome seeing as how the whole thing glows.

[lutzj]

question: beyond the difficulties with repairs and getting it into port is there any particularly good reason most boats don't build "down"?

The buoyancy force is stronger on more-submerged objects. An object with a sufficiently high height-to-width ratio just won't float upright. Ballast and fins/keels (for water resistance) near the bottom of a boat help but can only do so much. Also, if the bottom few decks are full of heavy ballast, the craft overall will only barely float, and big waves or fluctuations in seawater density could swamp the whole thing.

[Soralin]

I would never advise a nuclear powered anything in this system because of the instability of the power source and the unpredictability of the oceans. I am not even a bit convinced humans currently have the technology to make a nuclear power system that could power a whole society and still be safe enough to actually warrant living there. I mean, nuclear submarines work but their lifespan is about 25 years and the nuclear fuel lasts that long in the new ones, earlier models have to refuel their rods. Creating a system on the water to do the nuclear material work on would be kind of freaking insane- a nuclear sub built in 2000ish cost $1.8 billion US. I see a much more reasonable proposal in wind or sun or tide power, things that can be built and maintained on the ocean.

The lifespan of a nuclear sub's power plant is how much fuel it has in it. It lasts 25 years, because they seal it up with 25 years worth of fuel in it. If they put 40 years of fuel in it, it would last for 40 years. It's sealed closed with the fuel inside, to make it simple and self-contained, no input, no output (other than electricity and heat).

If you started with a breeder reactor, you could just toss enriched uranium directly into it with no refining necessary. And if you think constructing those is hard, realize that full self-sufficiency means that you're going to need your own semiconductor fabs, to make your own computers. Not to mention general (un)automated industry to make everything else, including itself. Assuming again you're going for true self-sufficiency, i.e. a self-contained civilization on a ship. Although maybe it was planned for a lower standard of living, or lower level of tech involved, bare survival minimum or such. But then, you probably wouldn't be able to make a new ship without resources from land with a lower level of technology.

[eSOANEM]

Something like some big massive bowl perhaps. You could have a big plain of farmland, with 20m+ tall walls on the sides or such, where the base of it is actually below sea level. You could make it big enough that waves would end up acting a bit differently, the crests of waves wouldn't go over the top, and the troughs of waves wouldn't go underneath, and it wouldn't move much with them, since it would only be an edge effect.

I suspect a disk is actually a better solution than a bowl. With a bowl, the edges will still be susceptible to vertical stresses due to the waves whereas, with a very large-draught disk, the entire platform is supported. That said, a spherical bowl will have less wetted area and so will have less drag (and so move faster) than the disk. So in practice, you probably want a spherical bowl will a disk on top with it all such that the edges sit with top of the bowl well below the water.

So you'll have trouble farming crops at any reasonable depth using sunlight (the formula also shows that at just 7cm of depth, half the yellow light will have been attenuated and that, after half a metre of sea water, less than 1% of yellow light from the surface wil lremain).

Plants don't use yellow light for photosynthesis. They use orange/red, and blue/violet. Here:

I was using yellow because it was the easiest to obtain a value for and is in the middle of the spectrum where there is the most light so will give a good estimate for the mean attenuation.

Furthermore, I also gave values for the attenuation of both violet and red so you got the extreme values and both colours were still attenuated significantly. There's certainly no way plants evolved for surface living could survive with that little light long-term.

I see a much more reasonable proposal in wind or sun or tide power, things that can be built and maintained on the ocean.

Wind and solar are useable at sea, but tidal is not. For tidal you need to take advantage of the flow of the water and so be anchored to the sea-bed. Away from other countries, the warp needed gets too big and it becomes impractical (if nothing else, the swinging room you'd have to leave between generators would be too huge to be practical.

Wave power should be possible though. It would be very possible to, in a flotilla, tow some snake style wave generators with you or, on a platform, have them on outriggers.

question: beyond the difficulties with repairs and getting it into port is there any particularly good reason most boats don't build "down"?

Yup, the surface area under the water (wetted area) is the main source of drag on a displacement (as opposed to planing or hydrofoil) vessel and the main limiting factor on its speed.

[Fantastic Idea]

Sorry, i did mean wave, and not tidal. one of these things makes sense.

[Izawwlgood]

I'm not sure if we are assuming some kind of nuclear powered city center while also making plans for a bunch of small atolls, do you want one or the other, Iz? I'm not getting a clear picture of what you're describing.

I'm just spitballin' here. I was envisioning something somewhat modular; say, an aircraft carrier, with a nuclear reactor providing lots of power, and a bunch of smaller platforms lashed to it. A bunch. Maybe even other aircraft carriers. Cruise ships, freight, etc. Smaller ships can be lashed to these, etc. Floating city, like in Snow Crash.

This idea is sort of dependent upon a lot of power, something nuclear, or magically efficient solar/tidal would be required for. And you CAN grow stuff below the surface, just obviously not terribly deep. In fact, the Australian dude who sealed himself in an underwater cycling biome was using algae for oxygen generation, and he was ~10m down.

[mmmCatSoup]

Because I have too much freetime...

[Hawknc]

You young kids today, you don't remember the classics: xkcdia

[omgryebread]

Though it doesn't meet one type of definition of self-sufficient, since it relies on trade, of a sort, with the land, this is already a thing.

Pirates in the Gulf of Aden, and to a lesser extent the Straits of Malacca have their bases on ships. Income is obviously piracy. Maintenance is taken care of by hijacking a new ship instead of repairing your old one. Navies are kept away by rotating hostages. A pirate "mothership" always has several hostages on board. Hostages held there aren't ransomed off until new hostages are there to replace them. The lack of desire of any country to actually arrest and prosecute pirates also helps.


I question the reason behind asking for a society that needs no trade, for fuel or other things. No nation in the world right now is self-sufficient, why put that restriction on the seafaring one?

[Trasvi]

Slightly tangential:
Could building a floating/flying/submersible city be good practice for any eventual star-faring efforts? Would we gain sufficient experience to outweigh the time and cost? If we could build a self-sustaining island-city, I think we'd learn a lot about self-sustaining space cities. Enough solar panels would generate power, though we'd need to learn how to farm space whales for meat.

I admit that I know next to nothing about agriculture, but would it be possible to have a (very) large structure of which 5-6 levels were dedicated to growing plants, ie all with artificial light?

[Ormurinn]

Though it doesn't meet one type of definition of self-sufficient, since it relies on trade, of a sort, with the land, this is already a thing.

Pirates in the Gulf of Aden, and to a lesser extent the Straits of Malacca have their bases on ships. Income is obviously piracy. Maintenance is taken care of by hijacking a new ship instead of repairing your old one. Navies are kept away by rotating hostages. A pirate "mothership" always has several hostages on board. Hostages held there aren't ransomed off until new hostages are there to replace them. The lack of desire of any country to actually arrest and prosecute pirates also helps.


I question the reason behind asking for a society that needs no trade, for fuel or other things. No nation in the world right now is self-sufficient, why put that restriction on the seafaring one?

Pirates, historical and modern, are something I've looked into as examples of how efficient legal systems can arise in the absence of a state, but I wan't aware of this model of resource management. Thanks for the info.

As for the self-sufficiency, thats probably partly a personal hangup - i put a high value on communities and individuals being able to take care of themselves, but theres also a practical element. No Nation is self sufficient as it stands, but if blockaded, most have the capacity to at least keep their citizens fed and watered, while a ship-based society lacks this ability if it's dependent on trade. A non-self sufficient sea-nation is also less interesting - its really just a long cruise holiday.

Slightly tangential:
Could building a floating/flying/submersible city be good practice for any eventual star-faring efforts? Would we gain sufficient experience to outweigh the time and cost? If we could build a self-sustaining island-city, I think we'd learn a lot about self-sustaining space cities. Enough solar panels would generate power, though we'd need to learn how to farm space whales for meat.

I admit that I know next to nothing about agriculture, but would it be possible to have a (very) large structure of which 5-6 levels were dedicated to growing plants, ie all with artificial light?

The latter is certainly possible, Meaux posted something similar earlier in the thread. As for the former, I've cited NASA reports here a couple of times, so presumable the research flow could also be in the other direction.

[Tyndmyr]

Well, a seafaring nation would need to produce something, certainly...you'd want something that you're advantageous at to trade for the things you can't efficiently produce without land. Furthermore, you'll have some additional upkeep costs that are non-trivial for keeping things floating.

Solar is probably not an effective power source. In addition to the added wear and tear of being at sea, land used for farming is not land used for solar, and frankly, most ships have a relatively low amount of sun-exposed area anyway. Wave power is an option, though only a really viable one while stationary. Same, same for wind.

You'll need significant power output for propulsion needs(dependent a lot on vessel and location. Are you going to be stationary year round, or seasonally located?), lighting(as natural light is, again, a very limited commodity), and desalinization. Extra energy can be used in growing things via artificial light, increasing the population supportable per ship. Long story short, to do this on any kind of large scale, you're probably going to want nuclear. If that's not an option, you'll want to be mostly stationary, either on a built island, or utilizing existing vessel design for cost reasons.

[eSOANEM]

Wave power is an option, though only a really viable one while stationary. Same, same for wind.

If you're using the snake style of wave power generators, there'd be no need to be stationary.

Likewise, depending on the direction of travel, movement might increase the amount of wind power generated because, when sailing into the wind, your induced wind builds with the true wind producing a stronger apparent wind. When sailing downwind of course, the opposite effect occurs.