Underwater habitat

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Underwater habitat

Postby Bluewater » Thu Nov 13, 2008 10:19 pm

Hi everyone.

This may seem a little 'out there' but would anyone like to comment on the following idea:

On a 40'x40' platform a 30' dome 15' height maybe? with integral floor is constructed.

The platform is towed into position then sunk to say 20m (60'), where it is attached to a very heavy anchoring mechanism.
The platform is removed for the next job, and the dome made boyant by filling with air and left suspended.

1) the forces the dome experience are now comming from the inside as air tries to force itself upwards until all air is pressurised to 3 bar.

or

2) an airlock is used to maintain internal pressure at 1 atmosphere, and crushing force of 2 atmospheres rests on the dome.

and

3) forces are exerted by the anchor chain equal to the displaced water - total weight of structure.


How thick should the dome concrete be?
How thick the floor pad?
How close should rebar be latticed?
How do I go about calculating the forces involved?
What are the chances of this structure upending?
Windows anyone?
Does anyone else think this will work?
Will anyone who knows please explore this idea with me?
Last edited by Bluewater on Fri Nov 14, 2008 3:09 pm, edited 1 time in total.
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Re: Underwater habitat

Postby domethink » Fri Nov 14, 2008 1:30 am

I thought about an under-water home, instead of under-ground. But I thought that water would eventually leak thru & make it very humid inside. Can concrete be totally water-proofed? Also, I wondered how to enter without getting wet, and how to drive & park my car in the underwater garage. However, a lake is a pretty good disguise for a home; who would look for it there? It would seem to be especially earthquake-proof. What would building code require for firemen's entrances in case of fire?

The Beaver
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Re: Underwater habitat

Postby Bluewater » Fri Nov 14, 2008 12:54 pm

In an ambient pressure design, entrance is made via an open hole in the floorpad.
Swim / scuba down to the dome edge then up into the interior... its that or a diving bell on a wire.

I worry for your car, though! Park up at the lakeside and make it look like an unatended fishing camp? Leave a cheap rod and some other fishing gear...

Here in the UK a floating structure is classed as a boat... no planning permission or land required especially if the vessel is based out at sea rather than in a lake or inland riverway.

In the UK I doubt I can obtain a suitable piece of building land (with permission) for £100,000.
As no land purchase or planning permission is required, this may offset construction, towing and anchoring costs.

Water passing through the dome structure in the form of vapour... unlikley.
The dome will be kept at a more stable temperature than it would be on land. This alone would help reduce water penetration / vapour ingress.

There are many products designed to protect ferrocement hulls from seawater.
One of these may provide a watertight barrier to moisture.

The air inside the dome is a different matter. It will require constant replacement and conditioning.
Moisture from breathing, and evaporation from the hole in the bottom pad or "moon pool" would need controll by way of an air conditioning unit.
Closing the moon pool from the rest of the dome would possibly help, and would allow for an airlock, if required.
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Re: Underwater habitat

Postby Bluewater » Fri Nov 14, 2008 11:49 pm

Lets put some figures in (from the dome calc)...

Diameter: 36'
Height: 16'
Stemwall: 1''
Radius of Curvature: 18.13'
Circumference: 113.1'
Floor Area: 1017 sq'
Dome Surface Area: 1822.12 sq'
Dome Volume: 10287.67 cubic feet
Stemwall Surface Area: 113.1 sq'
Stemwall Volume: 1017.88 sq'
Total Surface Area: 1935.22 sq'
Total Volume: 11305.54 cubic feet
second floor level 15.03 '
area at level 710 sq '

This gives:
domecrete thickness 0.3 feet 4"
dome concrete vol7ume 546.636 ft3
15.48 m3

floor pad thickness 1 feet
floor pad volume 1017 ft3
28.8 m3

displacement volume 10287.67 ft3
291.3468144 m3
298.3391379 Tons displacement in seawater
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Re: Underwater habitat

Postby Habitat Waterford » Wed Nov 19, 2008 2:25 am

Hmmmm, competition.
Hi Bluewater, yes great idea.
I have been working on this concept for close to 5 years.
I have just got back to Australia from Florida where I was working on the concept.
My project was picked up by a UK company who were building an eco resort in the US Virgin Islands.
The project is going ahead but has been greatly delayed due to the credit debacle.

As for an underwater dome.
The biggest problem is the ballast required for safe submersion and also deployment.
It took me along time with the help of NASA and NOAH personelle to figure this out.
At the moment, I have come to Australia to propose it here.

You can see some of my projects media by GOOGLEing "Shaun Waterford".
Look forward to chatting about this exciting concept.

Anyways, feel free to ask any questions.
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Re: Underwater habitat

Postby Dyolf Knip » Wed Nov 19, 2008 1:32 pm

I did the numbers for this sort of thing awhile back. The hardest part is getting the dome to sink to the floor. Concrete is heavy, but there's still quite a bit of empty space in there and it displaces an awful lot of water. Bluewater, what's the total volume of concrete used in making that 36' dome? Quick-n-dirty calc using 6" thick concrete yields ~33 m^3 of concrete for the dome plus 17 for the pad. Normal concrete is about 2.5x water density (what's a little salt between friends), which yields a total dome mass of about 125 tons. That means there'd be 175 tons of buoyant force pushing the thing upwards.

Checking densities of possible balast materials... lead ore would be pretty cheap and is very dense at up to 7.5x water density. Not sure you'd want that much lead laying around, though. Iron ore is almost as good at 5x. Granite is about the same as concrete, 2.5x. But either way it means keeping between 1 and 3 feet of solid rock on the floor of your dome in order to keep it on the bottom.

Not sure if the waterproofing of the dome would be a concern; the urethane foam is extremely waterproof (even under pressure?), it's only real weakness is water vapor, which isn't a problem for submersibles unless you're moving very fast (cavitation). But the pad would be exposed. Maybe build the dome normally, hoist it up on a crane, and spray the whole underside with foam?

On a similar note, how about a spherical (or nearly so) dome boat? Keep it weighted at the bottom, not enough to totally sink it but enough that it automatically rights itself. It wouldn't have any hull shape to speak of so moving it of it's own accord would be rather difficult. But it'd be very towable.
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Re: Underwater habitat

Postby Habitat Waterford » Wed Nov 19, 2008 3:21 pm

Gentlemen,
Here's some angles to ponder. I'll give guestaments as I don't have the calc in front of me.
Bouyancy:
To calculate buoyancy (neutral at first and then you have to calc the location neg buoyancy for things like long line swells)
you find the total displacement (volume) and then multiply the weight of seawater. (I think it is 63.4lbs/cuft.)
This will give you the weight you need for neutral buoyancy. For my concept, I have a "brim like on a hat" in which you can lower additional ballast if you want. I want to be able to raise and lower at will like a sub.
To calc the weight of the structure, I broke it down into two shapes. The semi sphere and the disk foundation.
I have the thickness of the semi sphere at 6".
My design of 20' diameter, needed approx 66 tons for neutral bouyancy.

After talking with Ralph Graham and Andrew South, the shotcrete (standard) is I think they said weighs 120lbs/cuft.
I designed the thickess of the base to be the primary ballast and came up with a 1.5ft thickness. The foundation can be mixed with gravel/lead/steel or whatever, to increase the weight.

I investigated a brilliant apparatus called "suction piles". These are hollow pylons which embedded themselves into seafloor after pumping out from the top. They can hold an incredible amout of weight and are used in the oil industry. They also can be removed easily by pumping water back into the top.

As you can imagine, location is very important. I chose a bay which was sheltered from long line swells and current.
The project I am bidding on now, I have the luxury of building it in a salt water lake. (let me know your email and I'll send the outline.)
It is a luxury because I dont have to deploy it. I will be pumping out the lake (small lake), building on the "seafloor", seascaping the area with artificial reefs, then pumping the water back in. (simular to how they did it for the hotel Atlantis.)

more to come.......
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Re: Underwater habitat

Postby Habitat Waterford » Wed Nov 19, 2008 4:29 pm

AIR/ POWER and interior EQUALIZATION. (1 atm)
My design is connected to the surface by an umbilical cord. (Hose within hose).
Which not only allows me to supply the habitat with power, telecommunications and air, but also allows the habitat to be equalized at 1 atm. My habitat is set in relatively shallow water < 50'.
You cannot have an equalized 1 atm habitat with a "moon pool" (opening at the base) as it would flood. (1 atm is superior because there are no compression or decompression factor for the aquanauts.)
So this means I needed an airlock. Quite simply, this is a double hatch system for entry. One exterior hatch and one interior.

more to come.......
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Re: Underwater habitat

Postby domethink » Thu Nov 20, 2008 2:14 am

Wow, your plans are way beyond the sticks & mud domes we used to build in rivers. Technology!! Interesting that homes can be classified as "boats". How is sewage to be handled? Environmental codes for both homes & boats ususlly don't allow dumping. Will cooking be done inside for long-term stayers, or will pizza be delivered? I like the earthquake protection, but the coming tsunamis will really raise a ruckus.

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Re: Underwater habitat

Postby Habitat Waterford » Thu Nov 20, 2008 3:12 am

For my prototype, I am seeking to break the world record for an uninterupted stay beneath the water. (69 days set by Rick Presley).
I am looking at microwave ovens for cooking and maybe even MRE's (Meals ready to eat.)
Appliances used for RV's based on a 12 volt system is what I am looking at.
Same with the sewage. There are some excellent RV toilet systems around. The one I have chosen is a cartridge system.
Quite simply, fill it up and then replace it. (reuseable). Then top side support crews would remove each cartridge to dispose of in surface side systems. (flush it.)

The beauty about all this is that it is all "off the shelf" tech and quite affordable.
As you can imagine, the RV market is huge and many excellent products are available.

To try to counter condensation, it will be routine to purge an on board compressed tank to "flush" the ambient atmosphere out each morning. I am also interested in O2 and CO2 trade offs by using onboard hydroponics.

Yes, very exciting stuff. Well, to me anyways. :o
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Re: Underwater habitat

Postby domethink » Fri Nov 21, 2008 1:07 am

Waterford: I forgot a few technical thoughts. It seems to me that with differential atm inside/outside, there will be driving force for more vapor penetration. Daily purging might solve this. ATM differential will require PERFECT airlock seals. Keeping inner space at 1 atm still presents a problem for someone who has been down for sometime outside of the dome before entering, since they have been at 2+ atm. Also, every time someone enters/leaves will require pumps to equalize pressures in airlock -- need adequate pumps & power. It's been years since I've dived; last time was under ice. These are great ways to get away from those #@#@@ cell phones. Best wishes to you if you try this.
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Re: Underwater habitat

Postby Habitat Waterford » Fri Nov 21, 2008 1:38 am

Well actually, if it is over 33ft deep, I think you have 40mins before Nitrogen starts to dissolve in the blood.
But you are correct, if Nitrogen does dissolve in the blood, you would get the benz entering a 1atm habitat.

I am looking for shallow locations where the pressure is less than 2atm.
Because of the interior being 1 atm, I have 2 hoses in the airlock. One high to allow airflow from the habitat to the airlock and one low draining into the habitat from the airlock. My airlock design is half flooded continually. When the exterior hatch is open the interior is closed. (of course). So in a way, the access tunnel (airlock) is like a moon pool. It itself is equalized when the interior hatch is opened (when the exterior hatch is closed of course.) Hence the drainage hose into the interior to lower the airlock water depth.
If the outside hatch leaks, it would compress the air inside the airlock if the interior hatch still has integrity. If the exterior and interior hatches fail, yes it would flood the access tunnel and then the habitat.
I'm looking at 6 dog waterproof hatches.
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Re: Underwater habitat

Postby GAP » Fri Nov 21, 2008 3:08 pm

Surely 69 days isn't the record anymore for staying down. Don't we have neclear submarines that have done six month tours and such submerged the entire time?
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Re: Underwater habitat

Postby angelofdodd » Sat Nov 22, 2008 7:57 am

I would also install,1)legs underneath,lower than the moon pool/airlock,and 2)some form of escape hatch in the upper shell...If for some reason boyency was lost from a loss of air pressure,or the water draining away,these precautions would keep inhabitants from being trapped and their situation from becoming F.U.B.A.R.!Matt
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Re: Underwater habitat

Postby Habitat Waterford » Sat Nov 22, 2008 4:01 pm

Matt, my design is more like an igloo. The access tunnel is the airlock.
You're right about the access hatch in the dome.
As for Rick Presley, look him up. Maybe subs are classified differently.
http://www.google.com.au/search?hl=en&q ... arch&meta=

As you can imagine by Bluewater's dome calc, the BALLAST is the most tricky, diabolical, bugbear in the whole project.

Where Bluewater has chosen a decent sized living space, BALLAST is where his concept becomes tricky.
I have chosen for a smaller habitat to make this problem manageable.
My idea is to have smaller areas but be connected by access tunnel to other living spaces.
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