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Revision as of 23:39, 15 October 2009 by Patri (talk | contribs) (Specific Design Proposals)
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This document describes our goals, requirements, non-goals, and ideas for the conceptual design stage of engineering. It is a revision of our previous design criteria, described in User:Patri/ConceptualDesignProposal2008.

Please do not edit this unless you are TSI Staff, but we'd love to see your comments on the Discussion page!


TSI's mission is to build permanent settlements on the ocean. Our current focus is on building SeedStead - a seastead for 50 residents, with commercial space, to be built by 2015. We don't yet know the target location and its depth, wind, & wave conditions - that will come out of our oceanographic research. Currently proposed locations include the Baltic, Mediterranean, and 200 nm off Los Angeles.



  1. Size. Target size is SeedStead - 50 people.
    1. Ideally, scale down well to BayStead.
    2. Must scale up, ideally to a city of 20,000.
  2. Safety. People survive in a bad storm. A 300-year storm may damage the structure so severely that it needs to be replaced, but that is OK. Occasional evacuations (less than once a decade) for extremely unusual/severe/dangerous storms are OK. If a part fails, it should not compromise the entire structure.
  3. Comfort. Platform movement/seasickness - People are relatively comfortable for 95%-98% of the time. The remaining 2%-5% they can be uncomfortable. They may need to relocate to the center buoyancy to avoid puking their guts out. Even then, some people will puke their guts out anyhow. Here are some thoughts on Acceptable_Motion
  4. Cost. Must be affordable - driving down costs is paramount. Comfort vs. cost trade-offs are permitted. Specifically, we'd like costs to be roughly comparable to an expensive first world house ($150 - $400 / ft^2). Less than that would be even better (comparable to a rural vacation home). Seasteads that can be purchased by individuals are extremely desirable. (Note: cost per ft^2 here is by interior space, not the footprint of the entire platform, so 3 decks of 1,000 ft^2 is 3,000 ft^2 of space) We will compare cost to ClubStead, and we'd like to get lower, definitely at its size, and ideally at SeedStead's size as well.
  5. Modular. Must be built in a modular fashion, so that it can be expanded incrementally and rearranged. It must include/support a SeedStead-sized module. It must support assembly at sea (perhaps only in calm conditions). Modularity is for several reasons:
    1. Primarily to let us start small and grow big, from 50-person SeedStead to 20,000-person city.
    2. But also to support dynamic geography. An individual section with its buildings should be able to be removed from the whole structure without enormous difficulty or cost.
  6. Cargo (Accessible). We need to be able to transfer people and supplies in 90% of weather conditions. This is difficult in the deep ocean, even in calm conditions, and is difficult anywhere during a storm.
  7. Anchored. We believe that anchoring makes life much easier and cheaper than dynamic positioning, and that the first seasteads should be anchored. Free-floating deep-ocean is for the far future.
  8. Draft. The structure must be constructed & deployed in a low-draft configuration so it can be built & launched from a shipyard on land. It can have deep draft when fully assembled/deployed, if such assembling can be done at sea. For large structures, this assembly can be hard to reverse or even permanent.
  9. Long Lifespan. The structure should be designed to last at least a couple decades. Don't want to require costly maintenance to get reasonable lifespan.


  1. Standards. Should comply with as many marine safety and engineering standards as possible/practical (ABS Classification, IMO, SOLAS, etc).
  2. Mobile - We definitely need to be able to move units from land to the offshore settlement. Also the settlement itself may occasionally need to move, it's ok if this is very slow and moderately expensive.
  3. Draft. Ideally, deployed modules can be converted into low-draft configuration to return to harbor. Extra-ideally, modules have low-draft even in full deploy mode.
  4. Different sizes play nice w/ each other (can include different-sized modules).
  5. Prototypeable at BayStead size.


  1. Mobility. Options:
    1. No mobility - cluster & individual seasteads are not easily moveable.
    2. Individual mobility - individual seasteads can move, but the group cannot. ie Tugs
    3. Cluster mobility. Likely slow & expensive.


The ClubStead spar platform design is our basis for comparison, although the smaller size of SeedStead may mean that its costs per unit area are higher. But we'd like to beat it on cost and motions.


  1. Pretty. The resulting structure has to have some appeal that people would want to live in it. We want to avoid a prison cell floating in the middle of the ocean design. (NR b/c this is engineering design, we believe we can add prettiness to any skeleton)
  2. Self-sufficiency. We do not require self-sufficiency (ie enough area for growing all food.)
  3. Defense. This is not a fort that needs to defend against a determined navy. Fighting off pirates is important, but a real navy or air force can easily sink us.
  4. Green. We do not need to be carbon neutral.
  5. Construction at Sea. We prefer designs that can be constructed at sea, but do not expect that to be economical, so land based construction is OK for now. But ideally there would be a long-term path for construction at sea, once our sea-cities are big enough.

Specific Design Proposals

TODO: Add short descriptions of each.

  • Ships - Likely modified to reduce wave motions due to our desire to prioritize comfort over mobility and operate in a slow-moving or anchored state. Could start with a cargo ship, cruise ship, or flotel.
  • [Semi-submersible](
  • Spar Platforms
    • Large - Oil platform
    • Small - FLIP, single column seastead
  • Multi-hull / Generalized catamaran - stability through large aggregate footprint of connected modules. Examples: minifloat, WaterWalker, flexible connections [detailled description coming soon].
  • Breakwater

(Note: linear breakdown is not possible; some concepts are best regarded as hybrids of some design principles. Working on a better classification system)

Which Designs To Explore In Detail

TSI believes we should next explore Multi-hulls & Ships. Breakwaters might be ideal in the future, but are lacking in incrementalism. Clubstead-type designs have been explored, but have been found not to scale down very well either.

Ships are the path of least resistance, and most likely to become reality in the near future. Multi-hulls look promising w.r.t. their ability to scale down. Combined with their shallow draft (in contrast with spars), they are deemed to be the most incremental option.


  • Clean up this page - change the names of requirements (Cost -> Affordability, Cargo -> Accessibility), add categories for new requirements and link to them.
  • Get feedback
  • Do a preliminary analysis of how each proposed design fits our criteria.