This post was written by George Petrie, Director of Engineering at The Seasteading Institute, in response to a number of posts that have appeared in our forums promoting designs for fully submerged seasteads.
The Seasteading Institute as a Forum for Discussion
The Institute is pleased to provide a forum for enthusiasts to discuss all aspects of seasteading and to explore all avenues for advancing the goals of the organization, and we encourage the open exchange of ideas on a wide range of topics. Moreover, we do not cast ourselves as sole arbiters of the merits of various ideas that are put forth.
Notwithstanding our commitment to this freedom of expression, we do feel it is appropriate to express our views on the establishment of underwater, or submersible seasteads.
In brief, the Institute neither encourages nor endorses the idea of establishing communities whose primary living accommodations are beneath the surface of the sea. We have adopted this view primarily because of concerns for safety, but also based on considerations of feasibility and compatibility with our vision of community building. Further discussion of these issues is provided below.
Safety Issues
As we have noted many times in our research reports and web postings, the sea is a ‘harsh mistress’ that can develop powerful wind and wave forces capable of inflicting devastating damage to vessels and structures. The hope of escaping these destructive forces seems to be a prime reason for advocating sub-surface seasteads. However, we feel it is important to underscore some of the more worrisome issues with the idea.
While it is possible to escape the full force of an ocean storm by submerging beneath the waves, doing so is not nearly as simple as some in the forum suggest. In deep water, waves produce an orbital motion of water particles that diminishes exponentially with depth, roughly in proportion to wave length (1). This orbital motion of water particles beneath the sea surface causes a corresponding variation in pressure that can cause objects on (or under) the surface to move up and down or side to side as each wave passes.
Because they diminish with depth, the pressure variations associated with a surface wave are no longer perceptible at depths exceeding about a half-wavelength below the surface. As an example, consider an ocean wave with a period (time between successive crests) of about 14 seconds and a wavelength of 300m, or about 1,000 feet; waves of this length are expected about 10 percent of the time in a typical open ocean location. To completely escape the sub-surface pressure variations from such a wave, one would have to be more than 500 feet below the surface. At a depth of 100 feet, the pressure variation with each passing wave would be about 50% of that occurring at the surface; at a depth of 50 feet, the pressure variation would be nearly 75% of that occurring at the surface. For shorter wavelengths, the attenuation occurs at shallower depths; for a 500-foot (150m) wavelength, 50% attenuation occurs at a depth of about 50 feet below the surface.
These pressure variations can cause a submerged body to heave, pitch and roll. In the presence of a severe ocean storm, these motions can be significant. Moreover, these pressure variations can increase the structural loads on the hull, and are particularly worrisome because of the additional loads imposed on windows and doorways that are often envisioned for submerged seasteads.
The take-away from the above discussion is that one must be substantially deeper than just a few feet below the surface to comfortably ride out a storm. A small submersible would likely be tumbled about rather severely at depths less than 50 to 100 feet. Even larger vessels like military submarines have to dive deeper than 100 feet to ride comfortably in stormy seas.
Obviously, the technology to go this deep exists, as submarines and other submersible vessels have demonstrated for more than a century. However, the technology needed to cope with forces under the sea is every bit as sophisticated as that required for oil rigs, passenger ships and other vessels designed for operation on the surface of the sea. For more information, one can refer to Rules for Building and Classing Underwater Vehicles, Systems and Hyperbaric Facilities, 2012, published by the American Bureau of Shipping. Topics include requirements for design, testing, materials, ventilation, life support and a host of related safety issues. The document is available as a free download at the ABS website.
(1) Wave properties are somewhat different in shallow water and/or near shore so anecdotal experiences in those situations may differ from what we describe above.
Feasibility
Numerous forum posts claim that submersible seasteads can enjoy the best of both worlds; they can rise to the surface and allow residents to enjoy sunshine and fresh air on vaguely conceived platforms without having to abide by the principles of Archimedes, which dictate fundamental requirements for buoyancy and stability. In reality, they will have to contend with the same issues of stability and reserve buoyancy as any other vessel, including docking with a supply vessel, landing a helicopter, or finding some other means of logistical support.
Equally pervasive is the false notion that submersible seasteads can be made cheaply. The reality is that submerged vessels must have sufficiently sophisticated and reliable ballast systems that will allow them to accurately maintain their target depth. For a vessel on the surface, floating is relatively easy, because there is ‘reserve’ buoyancy in the hull; if weight is added or buoyancy is lost (due to a leak), the hull can continue to float, albeit at a deeper waterline. But for a vessel below the surface, there is no ‘reserve’ buoyancy; if it springs a leak or simply wants to return to the surface, it must eject water from its ballast tanks or otherwise increase its buoyancy.
To be sure, people have sailed around the world on small sailboats and crossed oceans in rowboats or rafts. But these were expeditions taken on by adventurers, not proponents of an alternative lifestyle. The fact that one might successfully utilize a submersible as a novelty or a tourist attraction does not mean it is feasible to use as a permanent seastead any more than dirigibles or hot-air balloons validate the idea that humans can build castles in the sky.
Compatibility with the Institute’s Vision of Seasteading
Notwithstanding the ambitions of the Atlantica Undersea Colony, the totality of human existence has shown that human beings prefer (and are biologically adapted) to live on the surface of the earth, where they are free to enjoy sunshine and fresh air.
While we respect the rights of others to embrace their own views, the Institute chooses to allocate its finite resources towards furthering the establishment of floating communities, in the belief that these will ultimately be the preference of an overwhelming majority of potential seastead residents.
…si tacuisses….(Boethius)
For some special purposes submarine facilities could be very helpful: maintaining cables, tethered wave energy machinery; bases for ocean science; depressurizing returning divers…
Otherwise George Petrie’s discussion sums up why most humans will live on the surface very fairly. Well enough to save Yellow Submariners millions of $$s in time and investment. I shall put that Yellow image on my wall though.
“orbital motion” – sorry George but as a naval engineer you should know that the hazard for floating structures comes from intermittent liquid / air contacts and the buoyancy forces they create. – how deep do you need to dive into the ocean that intermittent air/liquid contacts on the hull are gone – 500 feet??!! – please! – wrong conclusions based on wrong asumptions – for a chatch up pls start here (http://concretesubmarine.activeboard.com/t45880972/submerged-protection-how-deep/)
I agree with George’s assessments, though I’m sure his data are based on a far more expert understanding of the engineering and oceanographic issues than I possess since he is a long-time student and instructor of naval engineering.
I really enjoy that the notion of Seasteading brings forward much creativity and thought-provoking ideas, but at the same time if we truly wish to move things forward we should focus on the most practical approaches.
As a related aside, while semisubmersibles have proven to be very stable, if a structure is large enough in plan (top down) view, then the added complication of active buoyancy control required by semisubs (and somewhat similar in complexity to full submersibles) may not be needed. A structure long enough to span more than a large wavelength can ride above those waves relatively unperturbed. Of course a large structure is more complex and expensive to engineer and build.
Jeff, the details in (http://concretesubmarine.activeboard.com/?a=24&categoryID=279555&subForumID=0) – just a few points: Right a surface float big enough (size of Nkossa or Ramform Banff) is a ocean base with comfort. Nobody is talking of “active buoyancy” control – it is a misunderstanding of the theme if you think just because the livingspace bubble is submerged it needs “active buoyancy control like a submarine. A structure to be undisturbed by waves needs to be big – compared to the wave – have you ever heard of the Draupner event? – this comes up 4 times a year or so…http://concretesubmarine.activeboard.com/t45822161/draupner-new-year-wave-and-its-consequences-for-seasteading/
All:
I ran across the following URL using Google:
http://usmilitary.about.com/od/navy/l/blsubfaq.htm
Item 21 says :
“Can you feel the waves on a submarine when it’s under the water?
It depends on how big the waves are at the surface and how deep is the submarine. During normal weather conditions, a submerged submarine will not rock with the motion of the waves on the surface. In fact, during even moderate storms the submarine stays perfectly level at its submerged depth while the waves crash above. In extremely violent storms like hurricanes and cyclones, wave motion can reach 400 feet or more below the surface. Though not as violent as on the surface, these large waves can cause a submarine to take 5 to 10 degree rolls. “
I’ve always wondered at what depth the does surface heavy seas go from uncomfortable to unsafe.
-Wayne
Wayne, you should consider that “can feel hurricane waves” is something VERY different to “being impacted by breaking hurricane waves” with thousands of tons of force. Also, you need to understand that some nuke subs are traveling at speeds of 70 knots – this makes them interact differently with the ocean than a static concept like the Ben Franklin does… (http://concretesubmarine.activeboard.com/f544145/concrete-submarine-project/) … More about Ben Franklin (http://www.nasa.gov/vision/space/preparingtravel/px15.html)
The ocean surface is clearly an extremely hostile environment during a hurricane. The question has always been what is the cost of building a safe structure that can withstand such a hostile environment? For below surface solution, how deep is deep enough? For above, what is the lowest cost structure that remains safe? How do those two costs compare? I personally do not know the answers to these questions.
-Wayne
a steel hulled submarine moving quickly thru the water might have a very different reaction to ‘turbulence’ than a moored concrete box with solid walls 16″ thick. remember that a solid weight also hangs below it. i tend to think the mass would prevent the island from shifting so much even as the water swirls around it. like u said Wayne, it should be tested in a computer. i just dont have the resources to do that. nonetheless i still think it would be rare that it needs to submerge anyway.
theres so many OBVIOUS things about the Bergstead that were completely overlooked by Mr. Petrie. one of them is the fact that, because its mooring is attached at a corner, that corner always faces into the current and effectively breaks the turbulence to a great extent. i heard a great phrase today, “generals always fight the last war – especially if they won it”.
Better term perhaps is Temporarily Submersible. Submerge only in case of storms, ships, attack and rogue waves that get seriously destructive. Pivotal Questions become “how deep and for how long”. Need air recirculation and refreshing capability for a period of several hours minimum. Great subject to mull over.
Yeah, while I can appreciate that TSI may want to focus their resources elsewhere, I really REALLY dont like their using the position they have to knock any possible avenue for seasteading.
Whether you are on the surface or below it, you have the possibility of sinking, and the danger concerns associated with it.
Rather than utilizing sub-surface realestate being a dangerous concept, I firmly believe that ignoring the extra-dimensional abilities that sub-surface utilization offers is itself dangerously limiting.
This is like designing the car all over again, and saying that electricity has no place in the design. If TSI succeeds in convincing people that sub-surface utilization is dangerous, it will take a long LONG time to convince people that in fact it has an equally legitimate place in the conversation and does a huge amount to improve the whole concept of seasteading.
pod hotel fiji – project .
It’s actually possible to have lots and lots of reserve buoyancy, and still be submersible.
Can have separate water-tight rooms, as recommended by SOLAS. In case there is large reserve boyancy, and low amounts of cargo, can flood some of the extra rooms.
Though of course would have to have bilge-pumps in them to pump out the water, preferably with a manual-pump that can be operated from the hallway.
Of course another option to submerge large-reserve boyancy boats, is to load up with lots of ballast in the form of large rocks, with enough load then the bilge-ballast could suffice for regulating up and down flotation.
My recommendation for submerging vessels is to have an air-lock, that allows exiting from the rear bottom of the vessel. Can also drop some of those large rocks to regain buoyancy.
TSI not officially supporting submerging, runs in the face of the fact that currently all life in the ocean is submersible or aerial in nature.
For instance the largest mammals on the planet, a great role seasteading model by any standard, whales. Sure sometimes they die/sink, but since there is submerged life at the bottom of the ocean, all of that carcass can get reprocessed.
It’s quite possible we’ll eventually have some deep ocean colonies, that could run salvaging operations, and even rescue drowning vessels.
The ocean may be considered a “harsh mistress” though she did give birth to biological life on earth, which eventually crawled out onto land. If you wish to be a seasteader you have to love the sea, love is forever greater than fear.
Humans much like aquatic mammals have babies with large amounts of blubber, that can swim from birth, indicating they are completely competent for living in a submersible aquatic environment, as the themselves can submerge, and swim to surface from the womb.
In fact underwater births are considered to be some of the easiest and most comfortable ways for a human women to give birth.
And, as one final comment on this farce of an article, I love how they put a picture of the Yellow Submarine, complete with technicolor stoner swirls, right in the middle of the whole thing. Why rely upon your argument alone when you can try to make your opposition seem ridiculous by associating them with drugs and fantasy, right?
Never thought Id see TSI stooping to politician maneuvers.
fair and balanced, just like rupert murdoch
Pretty dissapointed by ALL the directions http://www.seasteading.org has gone.
Guess they only want to get the contracts for airports.
ALL seasteads should have bombshelters , and ellmers is definitely the way to go.
To point out a deficiency that a sub “may roll ” without pointing out that most floaters would actually sink and become a total loss is not very productive.
Just another pointer for that oil platform on the home page.
Hi ellmer, I was referring to active buoyancy control systems for semisubmersibles, not submarines.
That said, it’s hard to imagine a submarine functioning without buoyancy control in the form of ballast and trim tanks and the air and water used in them, in addition to the control systems used to control them.
A problem with semisubmersibles is that they add a significant part of the complexity of a submarine to a ship, i.e. ballast tanks and associated active buoyancy control. Those systems tend to fail at inopportune times such as during storms.
Semisub Ocean Ranger sank with all crew lost when a rogue wave broke a window, flooded a buoyancy control room, and caused it to list in a heavy storm.
http://en.wikipedia.org/wiki/Ocean_Ranger
that is exactly the point – if we dismiss something than it should be on base of scientific and economic arguments not on base of misperception due to lack of knowledge … the idea that just because it is submerged it must be complicated is dead wrong…
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Jeff you’re right, I looked up the definition of “semi-submersible” it was totally-different from what I was intending to say.
What I meant was a fully-submersible craft, with a large amount of reserve buoyancy, that can function like a sailboat.
the “semi” in my intention was that it only acts as a submarine fully-underwater a part of the time.
In terms of the Ocean Ranger tragedy, yes, it wasn’t water-tight, and it wasn’t designed to be, as semi-submersible in their diction is a craft that is never fully submerged, on the ocean that kind of design flaw can be a serious issue.
In Phi Boat designs, we like to make sure that all aspects of a ship can be manually operated. From Ocean Ranger we learn that it’s good to have clear instructions of use, next to any levers or manually operated tools. Also it would be optimal if such tools could be operated from a top level of the craft in case of flooding. Though in a distributed system, it may be useful for people to be able to also bilge from a variety of locations.
In Phi Boat designs, we like to regard nature for examples of how to be. Fish have have only two eyes or “large windows”, in a heavily fortified section of their bow. They also have some smaller sensory devices on their sides to do with feeling the current and it’s properties. It is best to follow nature’s example and only have inset windows in the heavily fortified bow section of the boat just like our cheekbones and brows defend our eyes.
passengers are curious as to the location, they can go to the control room, or get a live-feed with maps, sonar readings and all that, as looking outside wont tell them much in most cases anyways “water water everywhere”.
If in sailboat mode, above-surface sailing, then can venture onto the roof for a scenic view in safe conditions.