Yesterday Nader Elhefnawy explored in "Diversifying our planetary portfolio" what technologies would enable a space settlement to be self sufficient. This is an ill-posed question as he partly sees:

“Species survival” is a strong argument for eventual space colonization—but given the sheer scale and technical demands of the task, a questionable justification for the most probable kinds of near-term investment in space. Indeed, it would even be a questionable justification for the most probable sorts of missions to the moon and Mars (which may actually be less attractive locales for colonies than fully-customizable “O’Neill cylinders”).

The assumption he then makes is that the goal is best achieved by cutting the costs of a self-sufficient settlement by cutting the mass required.

No, the cultural, technical, political and financial challenges of putting civilization on the path to long term survival via space settlement is not primarily about engineering. A self-sustaining space economy will naturally grow into one that is nearly self sufficient. The key in-situ resource is money. If the space economy can sell its tourism, entertainment or other services, more and more life preserving equipment will be sent to space simply to support normal economic activity.

I think there will be a cultural shift as the economic activity grows. Once space population hits critical mass, the continued growth of the space economy and population will be seen as inevitable. Then settlement can continue as an accepted and routine activity. Transportation costs will fall with volume of traffic and ark building won't be so expensive. Prior to that point, the best way to reduce the net cost of settlement building is to find the "killer app" for space that pays for the investment necessary rather than focusing on reducing cost.

The big problem is that nobody has yet come up with that "killer app" to make space travel economically viable.

I think an instructive analogy might be submarining. We have quite advanced subs, but they're military. We have a handful of research subs, and a few very specialized commercial machines for oil work and underwater cable maintenance.

But there are no underwater cruise ships and no seabottom cities.

We may have to wait quite a while before space settlement gets practical.

There are increasing numbers of privately owned 'submarine yachts', whose purpose is some combination of pleasure and ostentation.

Are mining company villages in the Canadian and Russian arctic a better analogy for the initial stages of interplanetary settlement?

There are a couple of new luxury underwater hotels being opened soon; one in Dubai, and another somewhere around Malaysia I think.

The mining company villages in the Canadian and Russian arctic are better analogies for why it will happen; the submarine talk is a better analogy for the technical challenges.

One of the main "obstacles" for finding that killer app (once tourism is maxed out), is that lots of stuff is cheap here on Earth, and getting cheaper. Real estate is plentiful. Rare elements are rare (by definition), but they're not THAT rare. Maybe the moon has an abundance of Helium-3, but we've got plenty of Uranium and Thorium down here (plus more efficient solar every day), which is almost as good. Most of the world's nations are "free" (or improving in that regard), so there's no overwhelming political reason to "escape" Earth.

Sometimes if I wonder if the first settlements in space will be some 21st century version of the Mormon exodus. Because materials just aren't what they used to be, and I don't see a gold rush.

Rand Simberg nails it! Except for this post I think the article and all the comments I've seen so far here and elsewhere have gotten more wrong than right. Too many people are thinking too far ahead in grandiose scales and aims and operate with self-defeating definitions of what constitutes as self-sufficiency. I almost want to call it "the O'Neill fallacy" but that's too unfair since he can't argue back. Let's just say we've seen it before and it just doesn't work that way; large scales and overly ambitious plans won't do anyone any good on their own.

Jon Goff has writen good stuff on this theme of "castles in the air" in the past, people might want to check that out in his archives over at http://selenianboondocks.blog spot.com/ (anti-spam measure chocked on "blog sp" so no link and remove the space in the url).

Step one or "killer app one" is more affordable prices for "smallish" payloads so people (individuals or small companies) can start getting real experience and data without building up a huge debt (or any debt at all if they meet success). Some things just can't be simulated well. Space tourism is great and I wish it the very best but an affordable kilogram price to orbit is the really exiting stuff in my opinon - not that the two won't support each other because they definetly will. We all know lots of good people are working on it, the rest of us should try our best to become their good/profiting customers.

A pretty good app for a self-sufficient off-world settlement would be miniaturized and distributed manufacturing. A example would be a Fablab the size of a walk-in closet that is capable of building new tools/machines and other Fablabs.

There is research that is ongoing in this area.

http://cba.mit.edu/projects/fablab/

The military currently is using mobile "Parts Hospitals" to replace parts for damaged equipment.

http://www.businessweek.com/magazine/content/02_29/b3792096.htm

Here's a group trying to build a self-replicating 3D Printer.

http://reprap.org/bin/view/Main/WebHome

I think space simply has more appeal than oceans for tourism. I would think a trip in a submarine (with good visibility and lighting to look at things with) would be incredibly cool. But two weeks in space would be mind blowing.

Habitat: as we love to bang around here one of the biggest drivers of a lower price per kilogram to orbit involves volume. You build one jumbo jet and fly it once, it's ridiculously expensive. You build a bunch and fly them thousands of times and, although the view is way neat, I want the aisle instead of the window so I don't have to wake up my neighbor to go to the bathroom.

(So more affordable prices is tied up in increasing demand and cheaper repeat usability and operational cost.)

Hermit: It's Sam actually, not Rand, but thanks.

I think that O'Neillians will muster the money to conduct their plans, but it will take much longer if no exports can be made from a space economy. I am a knowledge worker so my export can be my expertise if I can have a laptop, internet and phone connectivity up there. But the value of my product would be equal or less than what it is here on Earth in many respects. The first applications need to appeal enough to be worth millions of dollars such as movies, sports, entertainment and high end tourism.

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The submarine/ice analogies are somewhat strained because there isn't yet an economical industrial export from space that requires human presence. There's national prestige and tourism (ISS) which might be compared to adventure to see the Titanic or Antarctica or scale Mount Everest. There's also sport demand to cross Antarctica, science demand and a little bit of entertainment TV demand.

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Another way to bridge the gulf between demand for an off-Earth biome and supply is to educate people who want to pay for such a biome in how to make money.

Sam Dinkin: oops, I apologize.

I think that O'Neillians will muster the money to conduct their plans, but it will take much longer if no exports can be made from a space economy.

Of course the O'Neill plan was for the export to be solar power stations constructed from space resources and then sold to Earth.

Your subsequent comments about how your export could conceivably be your expertise given the right connectivity made me think of the Marshall Savage argument that everyone living in his space bubbles would be information technologists. But that's not enough. It's not enough to posit an export where being located in space is not necessarily a handicap. We need to posit an export product which is better worked on in space than here on the surface of the Earth. In my opinion, O'Neill acomplished this by pointing to SPS from space materials.