MDI Contructed Low Depth Submerged Seasteads with retractable Lilypads
March 19, 2009 at 4:54 pm #853
There is a ton of problems with submersible Seasteads. Keeping them in relatively shallow waters would alleviate many of those concerns and significantly reduce the dangers inherant in submerged habitats. At the moment I am considering a perminent location rather than a mobile vessel but the many benefits of mobility have caused me to give great consideration to this point.
I got the bug to live underwater, away from current societies, about 8 years ago. I’ve always imagined it as ‘habitat domes’ similar to those described in hard sci-fi novels dealing with colonization. You can imagine how happy I was to find the MDI system of designing low cost concrete structures with wide open interior spaces. Though I’m not a large believer in the ‘complete depletion of the world’s natural resources’ that has motivated much of the green movement, I have been actively studing the technology as a means to become self sufficient. Truth be told, I am a believer in the ‘good steward’ principles that can be found in Native American philosophy and some Christian belief systems… this fits.
The basic premise is to start with a single dome in relatively shallow water (maybe around the 50′ mark?). Extendable “lily pads” would allow surface access, air circulation, solar use and rainwater collection. In the event of bad weather, these could be quickly retracted to a submerged state to wait out the poor weather. These lilypads would mostly operate closed systems, like algae production, hydroponic greenhouses, solar and wave power units. Some more open systems would be air circulation, water desalination/rainwater collection, aquaculture (fish farming) and provide a point of access that does not require a submarine or scuba gear. I’ve had some trouble finding a fair system for human waste disposal but I think it could be incorporated into other areas like algae production, hydroponics and aquaculture. This has been one of the toughest systems for me to work out… I don’t know why.
Safety features would include a positive buoyancy ‘escape pod’ for quick surfacing and individual hip packs with a limited air supply for a manual surfacing.
These units would be easily to multiply and connect. The addition of mobility would allow for a more dynamic system of connecting units. I can’t imagine mobility would be a difficult thing to achieve in an underwater environment.
Using expandable/flexible tubing as an elevator using ballast tanks to raise/lower the platform or just use a positively buoyant platform in a tube that is filled/emptied of seawater seems relatively simple as well.
The first year will be spent getting as self-sufficient as possible, then focus could be given to maintain the established systems and construction of new domes for expansion.
Constructive criticism is welcome as many of you are much smarter than I. I’ve got a nearby river I plan to use to experiment with using concrete under water. My first dome probably won’t amount to very much but it’ll give me an idea of how the concrete settles in an underwater environment with a strong current. I can construct relatively large “lily-pads” in my garage and basement for trials and then deployment at the first dome.
-JasonMarch 19, 2009 at 9:33 pm #5257
I´m not exactly sure what MDI stands for, but the most efficient pressure resistant shape is a sphere, as far as I know.
A dome would have to be fixed to the seabed with some kind of foundation. A sphere could be simply weighted down and rest on the bottom. And you could move it at will.
If you want more mobility you need a submarine.March 20, 2009 at 12:34 pm #5259May 3, 2009 at 11:11 pm #5824
I’m currently jonesing on the submersible habitat dome concept as well. My preference, as is most assuredly yours, would be to maintain the option of mobility.
I had a thought concerning a safety/bouyancy system involving compressed helium (or hydrogren) tanks attached to telescoping portions of the structure. A quick flip of a switch could change the density of the entire module, and it would slowly float to the surface. Another system would be responsible for decompressing the structure to match the pressure outside (and to avoid decompression sickness).
There are obviously other methods than can be employed, but something like this, or other redundent systems, seems to be easily applied to a habitat dome to make it open ocean worthy.
There is no fate but what we make for ourselves. Each to his fate.May 4, 2009 at 2:46 pm #5831
Lilypad deployment and recovery would be a simple system of mechanical ballast control. No need to get overly technical with dangerous gases like Hydrogen, but sure… that’s the idea.
Originally, my plans are for simple submersibles that will not get too deep. It is not difficult to keep the interior at normal pressure. I could see an “elevator lilypad” which uses similar boyancy to move up and down a tube that fills with/or empties out seawater.
I haven’t refined many of these ideas for a while as my time has been taken up working on Seastead Outpost: Belize. I hope to make a remote controlled version when my time frees up some more… might have to wait til a few months into the Belize project. =) We’ll see.
-JasonMay 4, 2009 at 10:06 pm #5833
Yeah, I’m a fan of MDI, and have wondered if it could be used to build underwater domes. My concern is that being underwater makes everything more expensive, and things are already pretty expensive. On the other hand, you have the advantage of not having to deal with waves, which are one of the things that make seasteads more expensive.
Another concern is the psychological effect of no fresh air. Also access to power.May 5, 2009 at 2:23 pm #5847
My original idea… 8-9 years ago was to live in “habitat domes” beneath the surface. I know… screams of sci-fi geek dreams… but those original ideas have refined over time and I see the need for mobility.
Concrete can set underwater if done correctly. MDI itself is an inexpensive method of construction. Maybe I should focus on making a stationary dome complex… then since it’s already underwater, develop the method for making it mobile. That seems like a lot of wasted effort to me as stationary and mobile structures have different sets of design needs.
For power and access to fresh air, the submersible would have the ability to surface (needed for emergencies), but should be able to use the floating “lilypads” on the surface to meet the need. As for air, you’d be surprised how easy it is to draw atmosphere (no oxygen, but mixed atmosphere) from pressurized water. Ever open a bottle of soda and see all those bubbles? The liquid inside is pressurized, that’s why you don’t see the bubbles…. when the liquid loses pressure it releases the gases. Water is shown to hold the blend of atmosphere even at depths… so hit the “pressurized faucet” and let the fresh air out of the water.
Honestly, I’m more concerned about the psychological effect of limited sunlight and claustrophobic conditions.
-JasonMay 5, 2009 at 4:43 pm #5855
Yeah, I’m a fan of MDI, and have wondered if it could be used to build underwater domes. My concern is that being underwater makes everything more expensive, and things are already pretty expensive. On the other hand, you have the advantage of not having to deal with waves, which are one of the things that make seasteads more expensive. Another concern is the psychological effect of no fresh air. Also access to power.
Exactly. I see it as another viable way of solving the engineering issues associated with waves.
Problem is: you need to be somewhat below the surface to avoid the effect of waves, and add in some vertical space, and you are looking at a lot of pressure, and failure is not an option.
Ive done some calculations on submerged concrete structures, and it turns out you need quite a bit of the stuff. Material costs will probably be the limiting factor.
It seems like it could work, but what worries me is that it has never been done before. Not that this means it cant be done, but it does mean everything will be more expensive.
The psychology is not a concern for me personally, but its probably not a good idea to count on tourism as a source of revenue.May 5, 2009 at 5:15 pm #5857
Forces could be equalized by pressurizing the air in the module to approximate that of the water. The top and bottom of the structure will probably need some, additional reinforcement, as they could be 1-2 atmopheres off, but it would be little compared to the need to reinforce the entire structure to a 5-8 atmosphere differential without pressurizing the air inside at all.
There is no fate but what we make for ourselves. Each to his fate.May 8, 2009 at 1:29 am #5893
Oxygen becomes toxic at 2 atmospheres of partial pressure. Nitrogen narcosis sets in starting around 100 ft, around 2 atmospheres of partial pressure (more precisely 2.1) dependent on physiology … factors in it aren’t terrible well understood afaik. You get 1 atm total pressure per 33 ft/10 m. If you want to pressurize a dome and not die/be drunk all the time and die, you need to a) keep it no deeper than 100 feet, b) start replacing nitrogen with helium below 100 ft. There’s not much ocean that’s less than 100 ft deep not within 12 nm of a country (any?) So you would have to run a helium distillation system from somewhere, import it, or mine it. Most helium is gotten from natural gas wells, iirc. Additionally the initial charge of helium you got wouldn’t keep, you’d constantly have to buy more of it. That would happen with any gas that you can’t produce economically yourself, but it would be far worse with helium that doesn’t react with anything except maybe flourine and is so small. It’ll leak it’s way out of anything, fast. The costs would be simply enormous. Plus career deepsea divers (the guys who use these mixed gases regularly) aren’t known for their lack of chronic health problems. There is a lot of strain. IIRC even they are limited to a certain depth, ruling out the vast majority of the world’s oceans (assuming you’re pressurizing).
Pressurizing a dome, I think our physiology rules that out entirely. Now if you could get that oxygenated liquid breathing stuff they had in the Abyss …. It’s actually real stuff. I understand eating doesn’t work real well. And I expect the costs would be enormous^2. Perhaps you could pressurize a section between two nested domes to prevent taking on water, but then you’d still need to build the inside dome to resist the same pressure.
Ok so did some “research.”
Some crazy SOB went to 1752 feet on mixed gas! But take a look at all the stuff they need to do that stuff and you’ll get an idea of the costs.
OTH, they’ve got all sorts of structures and vehicles that allow people to explore and work at much greater depths not pressurized, heck the bathyscape plumbed the challenger deep way back in ’60.May 10, 2009 at 10:51 am #5929
Pressurizing sounds like a bad idea, from a biological, engineering and economic point of view.
Frst of all, as has been pointed out, humans anrt fully compatible with anything other than normal pressure.
Secondly: its going to be expensive.
And lastly: concrete doesnt like tensile forces. You can halve the maximum force by such a process, but one unit of tensile stress is much much more of a problem than 2 units of compressive stress, as for as concrete is concerned.
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