Life in an O'Neill Island 3 cylinder

[jollyreaper]

There's a lot more to it than "open space = inefficient = impossibly expensive".

Granted. I'm not saying I have all the ideas on what the insides of these things could be like. I'm just surprised there's no material on the net looking into it further. Most of the illustrations are stuck in the 70's.

While the old arguments for economics don't look as attractive as they once did, thanks to automation, remote control, and other factors, they aren't actually out (have you ever tried to actually remote control something in real time with several tenths of a second lag? Fucking frustrating for easy tasks, I suspect outright unbearable for delicate tasks. Automation helps a lot, but is no silver bullet either). Using space mass to profit Earth is still distinctly possible. If the competition down here changed a little, it might be right back in the game.

If we can do heart surgery over the internet, I think we'll probably be able to manage space construction. But we'll have to see.

There's new possibilities opening up too. Space tourism is still an unborn fetus for the post part, but it is slowly growing. They are looking into short hops now, and while that offers many benefits, it probably isn't the whole market. If people started taking longer trips up, you might start with a gimmicky hotel and grow into a tourist town, and see it take off from there.

The part about scifi I find so amusing is how we have all these design iterations on what the future will be before we ever get there. It looks extremely likely that we'll be seeing our autodrive cars on the road in the next few years. Certainly if we even had the powerplants to make flying cars a reality, we couldn't trust the masses to directly fly them and would have to rely on an automated flight control system. However, most scifi still shows manual controls on all the vehicles. I predict in 20 years we'll look upon that as just as quaint as the communicators on Star Trek not having screens or 1980's spaceships being full of CRT screens or 1940's robots being bipedal, walking affairs capable of speech recognition and yet visibly struggling to do arithmetic.

I have a feeling that the stuff we'll be able to do with telepresence and automation will completely obsolete most of how what we viewed the future as again.

It might follow a similar vein, but with military pushing the initial limits instead of private industry. This seems unlikely right now though.

The tourism thing seems more and more likely and is something I would have pegged as "least likely way to get people in space."

And, of course, there's still the old standby of "because it's there", maybe pushed on my nationalistic stuff or whatever, but ultimately going just because we can. This doesn't require god tech, just a good salesman.

That's what I call the political end of it. Unless it's within the means of an eccentric billionaire, someone's going to have to do a lot of work convincing a lot of other people the idea's worthwhile. Even the Virgin Galactic guy isn't completely self-financing his efforts. The Space X guy still needs government contracts to pay for his rockets. But that we're even talking about smaller, non-traditional businesses getting into what was once the exclusive domain of the government and military-industrial complex contractors is pretty heady stuff.

One of the classics is going into space to relieve the population pressures on Earth.

The direct approach never made much sense for that, but people in the 70's made that argument with an indirect approach - the space habs can increase wealth on Earth (energy availability, whatever), and rich people tend to have fewer children.

Hence it goes right back to the economic stuff.

I wonder about the possibility of creating more habitable land on Earth. There was talk in the millennium project about constructing artificial islands that would be self-sufficient ecosystems, sort of like a space colony at sea. They'd be floating saucers using calcium precipitated from sea water, a sort of artificial clamshell. As expensive as that would be, it would have to be cheaper than a space colony and it would be subject to the same political difficulties. If they could make it work down here, it would be that much more likely to work up there.

[Guardsman Bass]

There's new possibilities opening up too. Space tourism is still an unborn fetus for the post part, but it is slowly growing. They are looking into short hops now, and while that offers many benefits, it probably isn't the whole market. If people started taking longer trips up, you might start with a gimmicky hotel and grow into a tourist town, and see it take off from there.

That's what I figure the first non-military, non-government space station might come from. It's going to be a long time coming, though - right now, you could probably get the "zero g experience" just by doing high-up suborbital flights.

It might follow a similar vein, but with military pushing the initial limits instead of private industry. This seems unlikely right now though.

I'm not so sure, although I agree that it's not looking too likely in the near future that the military is going to set-up a manned facility in orbit (and they're banned from doing it on the Moon by international treaty, IIRC). I remember Sea Skimmer and Shep in other threads talking about how the advent of relatively cheap and powerful solid-state lasers might drive military aircraft out of the lower atmosphere. You could potentially see a development in that area, as the military planes fly higher and faster until they're pushing suborbital and possibly even orbital turf.

If that, as a side-effect, leads to better and cheaper space planes, that can only help setting up a long-term presence in orbit.

I wonder about the possibility of creating more habitable land on Earth. There was talk in the millennium project about constructing artificial islands that would be self-sufficient ecosystems, sort of like a space colony at sea. They'd be floating saucers using calcium precipitated from sea water, a sort of artificial clamshell.

You probably wouldn't need to go that far if you wanted to develop a seaborne colony. Just build some large floating platforms, or even just lash a whole bunch of boats together properly to create huge "rafts".

[lamm128]

A few hints on the economics of an O’Neil space colony habitat, in what I call a ‘mature’ development setting.

A good sized O’Neil, for 1 000 000 people. 100m2 per person for living space, 100m2 per person for transportation and industry, 100m2 per person for farming. Let’s put them on three floors, to simplify. Since 1 km2 = 1 000 000 m2, that’s 100 km2 or 10 x 10 km. Double this for the windows, 200 km2 total. For 3km diameter, 10 km circumference, 20 km long. About 850 million tons, including shielding.

1 000 000 people paying 300 000 $ for housing = 300 billion dollars available for construction. These are the same costs as on prosperous parts of Earth. If they cannot be built for this type of cost, they will probably never be built. Works out to about 300$ per ton of cylinder, all included, with shielding. About half the cost of a ton of steel today. That’s a big challenge right there.

The construction time may be relatively short. Chicago went from 300 000 to 1,7 million in about 30 years, 1870 to 1900. For a 20 year construction time, you would need to build 10 km2 every year, or about 1 km2 per month. 30 houses a day.

If the people in the colony live 100 years on average, 25% will be children or at school, 25 % will be retired and 50% active. So to answer the question ‘What will they do?’: Mostly, take care of one another, just as in any Earth city. Teachers, doctors, sales clerks.

Other possible revenues: Mining, mineral processing, power satellites construction and energy sales, low cost manufacturing (if 0 gravity can be used to save costs), building other colonies and spaceships, internet services, banking, finance, tourism.

The colony should offer the same services as an affluent neighborhood, with some advantages: Controlled weather, controlled access, good schools and interesting jobs. A hospital, retirement homes, The density of the colony would allow for shorter commute times than on Earth.

Of the 500 000 workers, if 50% work outside the home, the colony will need a transportation system for at least 500 000 movements per day. So a large integrated subway, or personal movement system. Large quantities of goods will also be on the move, so a cargo transportation system will also be required.

If a lot of people work in the 0 gravity area, there will be a complete transportation hub at the connection between the rotating and non rotating parts, with possibly hundreds of thousands of transits per day.

The colonies might cluster in groups, forming larger communities and markets.
Moving to a colony should not be much more expensive than changing cities today on Earth, including travel costs. So expect space elevators or very simple, highly reusable, SSTO oxygen-hydrogen rockets; or something new….

I expect there will be different phases of space colony construction:

The bootstap phase, the most difficult one, when the initial infrastructure is put in place at great financial risk, and the returns must be high. The most likely drivers being mining of high value ores (rare earth, platinium) or energy, or high value tourism. We’re not there yet. A few thousand people in space would be required.

A first development phase, where the habitats are more construction camps than communities. The habitats serve the Earth, creating power satellites and supplying larger volume ores (iron, nickel). Gerard O’Neil planned for much smaller torus habitats of up to 10 000 people at this stage. Squat cylinders with multiple floors might be another option.

A second expansion phase, when the habitats become the equivalent of affluent neighborhoods on Earth. The habitats are part of the Earth economy, possibly the most prosperous part. Immigration is important. Smaller O’Neil cylinders might be at their best in this phase.

A third, mature, phase, when the habitats become large enough and cheap enough to be independent of the Earth economy. Habitats make more habitats. This phase basically goes on forever, expanding to Culture Orbitals, Niven Ringwolds, Halos and other mega structures….

Because of the cost of the initial habitats, it is unlikely they will ever impact significantly on the Earth population. The first settlers will be those that would live in costly neighborhoods anyway. The first habitats will be just too costly to be slums. After a few generations though, you might get more variety…..

For the airplane questions, the station is spinning at 430 km per hour. A plane in the center will get carried along faster and faster the lower it goes, but with regards to the air around it will probably remain at about the same relative velocity. The pilot will have to look out for shear and turbulence, but they always have to anyway.

Hope this helps.

Michel Lamontagne
Otterburn Parc, Qc

[Swindle1984]

Just as a general thing, the simple explanations don't seem to hold up. One of the classics is going into space to relieve the population pressures on Earth. But if it costs a million bucks a head to put up space habs, then it would make more financial sense to pay couples a half million to only have one kid.

In my story, a comet about to hit the earth breaks up; part of it hits us and kills millions while doing long-term environmental damage. The rest of the comet, the part that missed, is guesstimated to return and actually hit us in 100 years. It's big enough that it could very likely be a global extinction event.

The entire planet freaks out and pressures their national leaders and the UN to do something, anything to prevent human extinction, the nations of the world unite for a project to save mankind. Naturally, the first idea is to blow up the comet or divert it somehow, but a media figure then asks, "what about the next comet or asteroid that takes us completely by surprise" and suggests getting our eggs out of one basket. A bunch of nerds advocate O'nneil cylinders to get us into space, pointing out that they can hold significant populations in space, can be used as bases to mine the asteroids and other planets for resources, and experience in building them would help toward building Rama-style generation ships in the future if we ever want to colonize other star systems. The media latches on to it, millions of panicked people think it's a great idea (and want to be the ones in space when the comet returns) and the governments of the world decide "fuck it, might as well, half of us are up for reelection soon anyway" and start building a small-scale cylinder pair to test the concept. It works, and despite the obscene costs, the various nations all contribute to building more cylinders as any politicians who object to the costs and/or logic of the project itself tend to get voted out of office or, in some of the less-developed nations, lynched by angry mobs.

Fifty years later, we have several cylinder pairs with growing populations actively mining the solar system for resources and manufacturing finished products for Earth, which has decided to ease some of the environmental damage by drastically cutting back on mining, industry, etc. and letting the space colonies take up the slack. Meanwhile, the people on Earth have the same short attention span as ever and many have either forgotten the comet will return or don't care because they figure they'll be dead by then anyway; they're a little pissed at paying such ridiculously high taxes to support the colonization effort, particularly since- oh yeah, originally it was affluent people and specialized personnel and their families (pilots, miners, construction workers, etc.) living in the cylinders, but once the panic wore off, most of the affluent and well-connected people decided they liked Earth better and moved back. And thanks to the growing world government (which is increasingly authoritarian thanks to bill after bill being passed to deal with the emergency of a potential human extinction and needing to ensure an end to international hostilities in the meantime) deciding the colonies were a good place to dump excess people and political undesirables, a lot of the people in the colonies are seen as pariahs by the Earth elite. If and when the comet really does return and they're still alive by that time, the various influential people plan to flee to the colonies and avoid the impact, but until then? Fuck those yokels floating up there. We shouldn't be supporting them with OUR money, dammit! Taxes are too high to begin with.

The colonists, meanwhile, are resentful of Earth because of the attitude, the "undesirables" and "excess" people resent being shipped off (even the ones who are glad not to be on Earth when the comet comes back) and the other colonists resent having uninvited/unwanted people dumped in their laps, and the colonists are also resentful because they don't see themselves as being treated fairly since they do a lot of resource mining and manufacturing of high-end goods and Earth thinks it can get everything cheap because of what they invested and continue to invest in the colonies.

Construction of cylinders has ground to a halt by this point, by the way. Earth can't afford to fund more even with the lowered expenses that come from having the materials and experienced workers already in space, and the colonists have little interest in building more because, well, they already have colonies.

So there's why there's cities floating around in space.

[someone_else]

Has anyone considered the inherent instability problems of a rotating cylinder? (I looked until page 3 of the thread, so I may have missed something)

Anything wants to rotate along their principal axis of inertia. An O'neill cylinder does not do so since it is longer than wide. A bycicle-wheel habitat (and a ringworld) does so, since it is wider than long.

Thus, if compensation systems of a O'neill cylinder fail, it starts rotating end over end. Hilarity ensues.

You can read this

It would be tumbling end for end in about ten minutes or half an hour.

Forgive me, but you're asking me to believe that you understand physics better than somebody who worked at Princeton University's Institute for Advanced Study. Can you give me a reason for supposing that?

A freely rotating object, isolated from the rest of the world, will wind up rotating about the largest principle axis of inertia. An O'Neil cylinder is supposed to rotate about its smallest principle axis of inertia.

Angular momentum is conserved, since the habitat is not banging into anything external to itself, but kinetic energy is not, since things inside the habitat can dissipate kinetic energy by being shaken around - and they will be shaken around if the axis of rotation fails to agree with one of the principle axes of inertia.

For a given angular momentum, rotational kinetic energy is minimized if the object is rotating about the largest principle axis of inertia. In an O'Neil cylinder, it is rotating about the smallest axis of inertia - so if the axis of rotation deviates slightly from the cylinder axis, the soft and loose stuff in the cylinder will get rattled about. As the rattling dissipates kinetic energy, we wind up with the largest axis of inertia being parallel to the angular momentum vector - the cylinder tumbling end over end.

To see this effect, spin a raw egg about its axis.

An O'Neil cylinder is like a pin balanced on its point. If the axis of rotation develops the slightest deviation from the smallest principle axis of inertia, that deviation will very rapidly grow, until eventually the largest principle axis of inertia is aligned with the
angular momentum vector.

For a hard boiled egg, the growth in the instability is quite slow. For a soft boiled egg, quite fast. In the case of the cylinder, if it was all steel, and no air, water, or human flesh, the instability would be reasonably slow. Assuming a cargo of people, earth, air
and water, the instability will grow pretty fast, at about the same order of magnitude as the rotation period, due to corpses and dirt dissipating energy by being hurled from one side of the cylinder to the other.

And here are formulas if you want to have a try (third post)

To be stable, the cylinder bust be rotating about the principle axis with the largest moment of inertia (this gives it the lowest rotational kinetic energy for a given angular momentum, meaning it cannot shed energy into other rotational modes).

A thin cylindrical shell - a hollow cylinder without endcaps - with mass M and radius R has a moment of inertia of MR^2 for rotation around its center axis.

A uniform circular disk - one of the endcaps of the cylinder - with mass M' and radius R has a moment of inertia of M'R^2/2 for rotation around its center axis. The cylinder will have two of these endcaps.

Thus, the moment of inertia for the entire hollow cylinder is MR^2 + 2 * M'R^2/2 = R^2 (M + M').

A hollow cylinder of length L, radius R and mass M without endcaps rotating around an axis perpendicular to its primary axis has a moment of inertia of M(L^2/12 + R^2/2).

A disk M' of radius R oriented perpendicular to its axis of rotation at a distance of L/2 - the endcap - has a moment of inertia of M'(L/2)^2 + M'R^2/4. Again, there are two endcaps.

Thus, for a hollow cylinder tumbling end over end, we have a total moment of inertia of ML^2/12 + MR^2/2 + 2 * (M'(L/2)^2 + M'R^2/4) = L^2 (M/12 + M'/2) + R^2 (M + M')/2

If the cylinder and endcap both have a uniform areal density D (probably equal to 1 ton/m^2, as this is sufficient to cut the dose from cosmic radiation down to levels without known long term health risks), then M = 2 * pi * R * L * D, M' = pi * R^2 *D.

For rotation about the cylindrical axis, this gives
I_z = pi * R^3 (2 * L + R) * D.
For end-over-end tumbling, on the other hand
I_x,y = pi * L^2 R (L / 6 + R / 2) * D + pi * R^3 (L + R/2) D
And we need
I_z > I_x,y
for stability. This gives us the condition
R^3 + 2 * L R^2 - L^2 R - L^3 / 3 > 0
Since it is late, I'm not going to solve this cubic inequality now (or check my work, for that matter - others may wish to look it over for accuracy), but will note that cubic equations do have closed form solutions, so you can find the allowed values of R in terms of L that give you a cylinder that rotates stably about its axis rather than tumbling end over end.
http://en.wikipedia.org/wiki/Cubic_equation

Luke

[someone_else]

That specific post has a couple big flaws

Can you tell the second? The layout of that site is confusing, I'll take your word.

O'Neill cylinders are never built individually. They always come in pairs, connected on the ends. They rotate in opposite directions so the angular momentum cancels out on the whole.

Yeah, knew that detail. I just don't like to make things that can fail and fuck up everything if I can do stuff that can't fail like that for a similar price. And this is something other people may have not guessed (I have not seen images of o'neill habs with two counter-rotating cylinders, only stuff like this where the connection isn't obvious, at least to me).

Is there any good reason to have another thing that can catastrophically fail like that (you have already heat management systems that can force an evacuation if they break down)? Say, A stanford torus will work fine.

Anyway, you can also use dynamically-adjusted ballast tanks and skip the problem of mating two of such rotating cylinders. Although maybe its unpractical at that size.

But, since they are so massive, it will still take quite some time for the situation to become critical (well over a month).

How can you calculate the time it will need to destabilize? I'm curious.