I started thinking about how 3d printing a seastead might work and this is what I came up with.
First, to 3d print base and all this would be something that you would need to do in shallow water. Most likely on a seamount then.
Bottom up construction would need you to somehow displace water to get whatever you are adhering to, to stick together. This would mean you’d need some kind of vacuum chamber as big as what you were forming and have to seal it to the seabed in some way. Doesn’t seem realistic.
For top down construction, unless you are in really really shallow water, what ever you are building is probably going to be too heavy to lower to the bottom unless it is a hollow caisson and then why not just build it on land and float it.
But what if you could lower as you were building?
Here’s my idea. This is what molten basalt looks like when you pour it into water.
Notice how it pours pretty straight until steam from the bottom forces it to curl? The bottom also forms pillow lava much like under water volcanoes.
Well, if you are pouring from enough distance it should be cool before it hits bottom so no pillowing and no curling. You would need to pour at an exact continuous speed to keep it from bulging or breaking though. That shouldn’t be real hard since it’s pretty viscous. The steam pressure should be equal on all sides. So what you would end up with in calm water would be an obsidian like basalt rebar from top to bottom. Of course there will be some current even on a seamount, so it would look more like a bent or diagonal rod when you are done depending on the speed of the current.
Well it doesn’t have to look pretty as long as it is functional so over-pouring, so it blobs up, would give you something that looks like an inverse cone or under water volcano by the time you are done. The more you pour in the same spot, the wider it would get. You could pour it to look just like the picture and it would work fine.
Basalt is pretty common. You can buy it in powder form. To melt enough to get the equivalent of
of a 50 cubic meters would take about 300 tons if my math is right. (6 tons per cubic meter is a rough guess) The only ton price I could find was for snow sand basalt and not powder but it was $8.50 so lets just say $20 a ton to be safe. That’s $6000 in materials for forming an island made out of the same material as Hawaii. And you are going to have to pay for it to be hauled to you and for the ship to wait while you melt and pour it.
Now there is a big cost I am leaving out. To melt it, you are going to need a big hopper and a furnace. There are ships with conveyors that can dump it into your hopper. Since you are dumping in a big blob, you can dump it as fast as you can melt it. For melting, you’re gonna need plasma torches and a tap. I’ve already seen a system that uses 2 torches and can melt 200 kg an hour, so lets put in 10 torches and melt a ton an hour. It would take you 300 hours to melt and dump it. That’s going to take 2.125 MW per hour. Lets round up and say 640 MW total. That works out to about 60,000 gallons of diesel if the generator is sized right. At $2.25 a gallon that $135,000 in diesel fuel and a ship to haul that and sit and wait.
Now if you melt and pour 16 hours a day. It’s gonna take 19 days and you’ll need the ships to wait for that long. I have no idea what it cost to charter the ships, but I am guessing that it’s much cheaper given the shipping industry right now. Let’s say $15,000 a day x 19 = total of $285,000 not including hauling it there.
I’m thinking that $700,000 sounds realistic for such a project. You could use an underwater dredger since the seamount is surrounded by the same material you are using as well. That would save you paying one of the ships to wait. But now you’d have to pay 2 or 3 divers for 19 days. You might be able to get everything under $600,000 that way.
It seems like your biggest expense would be ships waiting so maybe if you built 2 furnaces you could cut the cost even more. Perhaps you could buy the ship for the fuel and everything else and then sell it when you were done. The second biggest cost would be power and there is not much you can cut there. Material costs seem to be negligible. Your cost for going bigger would mostly be constrained by power as you could save time by using more furnaces and materials aren’t much of the cost.
Even at $700,000 you are building an island for cheaper than a lot of islands are to buy and this one doesn’t come with a government.
If you went with the pure basalt route your island would be built better than most volcanic islands are and those take centuries to erode in most cases. You could smooth your island out on top while still hot, or form it into a bowl on top and pour soil or sand in it.
I know this is way out there, but it is something to think about. Especially if you start looking at the shallow areas that are just below the water.