Ok this one's weird but it should work. The sea stead makes no attempt to stay afloat in big storms, it simply sinks. It has ballast tanks like a submarine, an air tight hull that is mostly open space and is floodable and a core structure that is actually a working sub. Every thing packs away into water tight lockers or the core structure leaving a bare room or even open decks. Fill the ballast tanks and down you go sitting below the waves at about 10 meters.
- Material issues - Structural metal and/or composite design. The main flood-able section would need to be sea water tolerant materials and easy to clean. It won't be submerged for too long so fowling should not be a problem.
- Will need a pressure tight hull for the core, probably ferro-concrete. http://imulead.com/tolimared/concretesubmarine/ is a good example of the core structure.
- Heavy pressure doors, pumps, a snorkel is required. The snorkel can be a powered system blowing air down into the vessel so its never totally underwater.
- Can be any shape but rounded surfaces allow water to flow off and can be multihulled so should be very stable.
- Shallow submarines are a well established field of design. We aren't talking military hulls.
- There are some active systems and controls needed so there is a chance of that going wrong but we can automate some of the control processes.
- Not clear how we make boats inside safe during hurricanes. A big submarine sea stead could have an internal dock.
- Dependant of good weather forecasting and someone being competent to batten down the hatches.
- In good weather, flat seas it would be ok. In heavy seas it would sink 3 to 10 meters down to get below the rough seas. If storms are too frequent there could be a lifestyle disruption problem.
- Depends on size and how cheap we can make the hatches and ballast systems. Pressure tight windows are very expensive and should be avoided. This may be changing. Video based "virtual windows" on the surface of the hull and the buoys will help with situational awareness.
- Best done as an open deck with tent like structure or a deck with domes on it.
- Can be modular but the hulls will need some space to spread out underwater.
- Because the hull can submerge and surface we could build submerging dry docks that sink down to allow a freighter or container barge to float in and then float up to lift the vessel above the waves the vessels then move together on the waves.
- Free Floating
- Yes. A system of buoys on reel in/reel out lines controls depth.
- yes a very large hull is cheaper that smaller ones.
- yes but slow. Unless it has a bow and or catamaran design.
- Three times wave amplitude. If we go down to the sea bed in shallow water there may be hull breach and environmental impacts.