Engineering Parallels Between Ephemerisle & Seasteading

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There are a wide variety of opinions in the seasteading community about whether Ephemerisle is a plausible path to full seasteading. [Here’s my pre-event pitch of why Ephemerisle is useful](http://seasteading.org/blogs/main/2009/08/05/why-ephemerisle-matters-to-seasteading). Post-event, I have an additional thought.

Our [Ephemerisle](http://ephemerisle.org/) structure and setup basically worked as plan, with a few exceptions. One is that it took longer than we expected, and was not completed by the noon Friday starting time (although everything did come together for Saturday evening). Besides that, the biggest technical issue had to do with anchoring (ie location control).

Ephemerisle Saturday morning,
platform moved to the shore,
houseboats not yet moved

Friday night, much of the main platform was together, but the huge sea anchor our platform engineer brought didn’t work in the Delta mud. He made some gravity anchors out of concrete and rebar which were sufficient to hold the platform, but he was not comfortable docking all the houseboats and homemade structures to the central platform and having the whole collection moored by the gravity anchors. We also had concerns about anchoring the collection of houseboats as one unit, as mooring 9 houseboats with 1 or 2 houseboat anchors risks an anchor or line giving.

The obvious solution is to parallelize, but anchors don’t parallelize well, for two different reasons in two different setups:

First, suppose all your structures are one unit, and you drop multiple anchors, each of which is individually too weak for the whole unit. The constant motion of the structure (in the wind, waves, and currents) will pull different anchor lines taut at different times, and you can’t easily maintain tension on all of them at once, so they’ll pull out one by one. That’s why many small gravity anchors on the main platform did not constitute a solid anchorage.

Second, suppose you anchor each structure (or group of a size that a single anchor can hold) separately and then try to have some kind of flexible bridges. Each structure has what’s called a “watch circle”, which is the area on the surface that it moves over as wind, currents, and waves change. Because of how anchors are set, anchor lines run diagonally, not vertically, and so the watch circles are several times the depth. Each structure also has a “mooring footprint”, which is the area spanned by the anchors and lines. Again, this is several times the depth. And unfortunately, neither can overlap – when watch circles overlap, structures may bang into each other, and when mooring footprints overlap, anchor lines can tangle. So this means the structures must be widely separated, which would make Ephemerisle not be a single community.

So we ended up using the shore as a fallback – we tied the main platform to trees on shore, tied the houseboat collection to separate trees on shore (so both had solid moorings and tiny watch circles), and we built a [rope barge](http://www.flickr.com/photos/11338642@N00/3991136760/) to go the short distance between them. One of our major goals for incremental progress for Ephemerisle 2010, of course, is to solve this anchoring problem without cheating by using the shore.

In the months since the event, Eelco has been working at TSI on an overview of seasteading engineering considerations and solutions. And the single biggest challenge he’s found, besides the obvious one of dealing with the waves, is…location control! While the situation is more complex, the exact two same anchoring issues we encountered at Ephemerisle still come into play. The fact that anchors attached to the same structure don’t parallelize (so how do you anchor a city?), and that moored structures have large mooring footprints and watch circles and so you can’t just individually anchor multiple structures. (Watch circles are proportional to depth, so moor in 1000m water and you’re talking about a footprint of a square mile or more separating each structure – not much of a city!)

There are several potential solutions to this, but I’ll save them for Eelco’s paper, because my main point is not to explore location control issues. My point is that even the first Ephemerisle, in the protected waters of the Sacramento River Delta, brought up significant engineering challenges _which directly apply to open-ocean seasteading_. Even I, as an avid proponent of Ephemerisle as a viable incremental strategy, did not expect this much of an engineering parallel.

Now, I’m not pretending this is a complete argument for the viability of the Ephemerisle strategy as a path to true seasteading. Perhaps it is merely a coincidence. But I think it’s a striking data point, and I’m glad that Ephemerisle is one of the parallel paths we are pursuing, along with academic research, professional engineering, developing real businesses, and more.

One comment

  1. i_is_j_smith 6:34 pm

    Normal gravity anchors will never work on a massive scale. That is why vertical anchoring is the only real option.  Look to the oil industry for these types of things.  While they may be killing the environment, the economy, and good sense they know how to anchor a large floating structure in the deep ocean with excellent location control.

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