What are the design considerations for my underwater settlement?

Communication

Seawater is highly resistive to radio waves at the frequencies we usually use them. (see page 7, section Sea Water.) However, at lower frequencies, 10-30 kHz, it is entirely possible. Unfortunately, this frequency allocation chart shows that the entire 10-30 kHz range is occupied. You'd be interfering with other signals, if you're using the same systems. However, you could set things up in your world so that the 10-30 kHz range is completely empty, at which point you can put radio communications from your city in it.

Your other option, since you're not that far underwater, is to build a big antenna extending above the surface, which you could then assign any frequency to since air conducts radio transmissions.

The alternative, which you can use for many of these sections, is a tunnel leading out that takes you to the surface.

Transport

Transport around your city is not a problem - since you're pressurising the whole area, you can just use regular methods of transport.

To get in and out of your city, your setup of airlocks and submersibles is sufficient, but you might want to consider big submersibles for that many people. The alternative, as I alluded to, is to use your communications tunnel to move people as well.

Power

This answer is going to get very boring very quickly if I just keep saying "use the tunnel". However, you could do, just run a big cable down it. The alternative, which is slightly more interesting, is to build an osmotic power plant or salinity gradient power plant, which uses osmosis between and fresh water source and a saline water source to create power. Assuming you also have a desalination plant set up for water, you have both required water types.

Air

Run a pair of tubes up to the surface and stick big pumps on both of them. One of them should pull air out of the underwater dome and one should put air from outside back into it. You could also add some filters if you want really clean air - this might also work as a health centre where people with weak immune systems could come to because you've cleaned the air. Just make sure you decontaminate every visitor.

Waste

You need transport for this, basically. The simple solution is to take bags of waste out on every submersible trip and bring in supplies. You could also have some fun by installing a flexible tube leading to the surface and putting some targets around on the surface... trash bag shooting becomes your new sport. Shoot them with air pressure.

For waste water, do what every country does with their waste water already: recycle it. Clean it out, filter it, sanitize it, and put it back into the fresh water system. (If this disgusts you, don't worry - you're drinking the water that someone flushed down the toilet a month or two ago.) You can dump the remaining solid waste into the sea. Again, if you protest violently against this, countries already do it and have done for a very long time.

See also eharper256's comment below this post explaining some alternatives.

posted about 9 years ago

ArtOfCode‭ staff

101 reputation 4 65 10 3

Someone is trying to do something like this on a smaller scale.
But you could do better.

Construction
Thankfully 50 meters isn't all that far down, so while it will take some heavy duty construction, it won't take Rapture level technology.

Power
You could use a few different renewable power technologies. Wind is easy. Tidal power might be an option if there is land somewhat close. Biogas could be generated on site. There has been work on using algae to produce fuel. Hydrogen could be produced by electrolysing water from the Water Recovery System to produce oxygen and hydrogen.

Water
Desalination, evaporation, and recycling are going to be your best options. Desalination and evaporation could be combined with the power generation if you go with biogas or algae fuel. Keeping it self contained like the ISS will help as then you'll only need to replace a little instead of a lot.

Wastewater
Use the same methods used on the ISS. You want to replace as little water as possible.

Communications
Having a radio buoy would be an easy way, and could easily include satellite too. Just raise it on a wire, pull it down in really bad weather. Keep spares.

Transport
Submersible would be one good option, but you could have a floating platform with a elevator tube as well. This would allow easier coming and going, and help with communication and air. Plus it would give you a place to dock boats.

Air
Similar to the ISS again. Electrolysis from the water reclamation system, pulled from the surface, or recycled in a green house.

Trash
This would be the hardest one. You'd want to remove as much of it as possible before it got to your city. No extra packaging, make as many things as possible biodegradable so they can be composted, recycle as much as you can.

Food
A few greenhouses are going to be important for food, fuel (algea), air, water filtration, sanity, etc.
I'm sure fish will be another big part.
Probably import some stuff, but you'd want to be as self sufficient as possible.

Windows
If you can't have windows then what's the point If being under water in the first place? Pressure is an issue though. As WhatRoughBeast points out, big windows are probably impractical, though with the right laminated materials and with enough thickness it's probably doable. The other option is to have smaller windows, but more of them.
The window on this is designed to go down to 300m:

So you get a lot of them and put them all over. Being stuck in a tin can 50m under water without being able to look out for any length off time would be a horrible vacation.

posted about 9 years ago

AndyD273‭

1 reputation 8 213 1 0