Space colonies of the future as imagined by NASA in the 1970s
rarehistoricalphotos.com
rarehistoricalphotos.com
What I'd prefer to see is a space construction that is continuous. Imagine a ring station, but one that is cellular in nature- lots of smaller modules that together form the huge station. This allows one to construct and add further modules over time, growing as needed.
The beauty of this design principle is that we could start today. Design the first iteration of these modules, with the intent to fit them into SpaceX's Starship (or whatever heavy rockets come next). Launch 10 or 20 of them, connect them, and spin them up to 1/5th gravity, something not too hard to do. Add modules in the centre of the ring that are zero-G, where zero-G things can be done- but allowing those who live on station to live in mild gravity at least.
All the while, you can dream big. You can plan for how this station goes from 10 or 20 small modules to thousands.
Being huge means less inner ear dizziness, spinning small and fast is stressful on materials and makes humans sick. And docking would be a major POA.
If we are talking km diameter structures holding station in system, making it rotate isn’t going to be a drama.
Sadly, they do rather require "magical" technology....
Other challenges include how to spin it up (and down) safely, how to dock with non-spinning things, how to deal with changes in mass distribution, and how to put thrusters on it for use when it's spinning. None of these is impossible, but together they create a serious engineering problem, and the size of the whole thing is ultimately the dealbreaker.
Docking would be via a central hub. Ships would have to match rotation to dock, but it shouldn't be too hard. My conclusion is that if the money and/or political will were there we could start doing this today, but the project would be hugely expensive (even with SpaceX cutting launch costs to a fraction of what they were only a few short years ago) and once you have it built it will be looking for a purpose. It would be cool for people to basically commute up to the central part (via elevator) to do zero-g research stuff, then commute back to the ring to live and avoid the various health problems with long term zero-g living like bone density loss.
You can even build a simple starter station that has only two segments on opposite sides of the central hub. This is less cool since you don't get the jogging path around the station. If stability is an issue you could also include a computer controlled mobile counterweight on the ends. I also had the concept of building it as a double hull with a layer of water between the inner and outer to reduce radiation flux and absorb micrometeorite impacts.
But in the end you are still talking about a hugely expensive project that solves problems that aren't all that bad yet. About the only way I could see this being built is if Elon decides to go all in on space and liquidates his fortune to build it. The instant some annoying bean counters ask the question "is this the best way to spend this money" the project is dead.
From a radius of ~300m onward you'll see green lights (= good for people) for all considered parameters. RPM drops from 1.7 to 0.5 for a radius of 3000m.
If you made something like a gravitron ride on the moon, would it take a slower rotation speed to reach perceived 1g than if you spun up a ring station in orbit? This calculator makes it seem like you could get pretty close to 1g with just a bullet train running on a 3.14 kilometer loop.
It seems like the main thing stopping earth trains from being faster is that most of our tracks were built a really long time ago and it's not worth the effort replacing them, but if metal is readily available and you're laying new track already, designing for ~300km/hr wouldn't be that much of a stretch no?
The main thing stopping earth trains from being faster is politics, not engineering. Trains have been occasionally going over 300 km/h since 01955, decades before maglev. The Shanghai Maglev Train has been running at 430 km/hr since 02004. The Euroduplex regularly runs 320 km/hr on regular 1435mm standard-gauge rails and reached almost 575 km/hr in a test in 02007. 300 km/hr trains have been in regular service since 01989. There are several other train lines that run over 300 km/hr, in Taiwan, PRC, France, Belgium, Saudi Arabia, Japan, Germany, the UK, the Netherlands, Italy, Spain, Korea, and Switzerland. Soon India and the US will join them.
The big advantage of maglev is actually not smoothness or absolute speed but acceleration and deceleration.
https://en.wikipedia.org/wiki/Euroduplex https://en.wikipedia.org/wiki/High-speed_rail#Speed https://en.wikipedia.org/wiki/List_of_high-speed_trains https://en.wikipedia.org/wiki/Maglev#Comparison_with_convent... https://en.wikipedia.org/wiki/Taiwan_High_Speed_Rail https://en.wikipedia.org/wiki/Bombardier_Zefiro https://en.wikipedia.org/wiki/Centripetal_force https://en.wikipedia.org/wiki/Euclidean_vector#Addition_and_...
Having the whole habitable part of the station rotate may be fine most of the time, but it makes docking with ships more complicated. If the ship can't be spun, then you can either use some kind of rotating docking collar (which doesn't have to be perfectly airtight if it's only used once in awhile, but it still has to be pretty good) or you have put on a suit and do a spacewalk just to move things back and forth between the station and the ship which sounds kind of inconvenient.
(I guess there's actually another solution which is to stop the station spin whenever docking with a ship. That costs energy and/or reaction mass, though, and you'd have to deal with whatever disruption switching to zero-gravity brings.)
I can see why they might not have wanted to deal with this for ISS, but maybe for a bigger/more ambitious space habitat we'll want to do it.
Another possibility is to have the docking station completely disconnected from the outer ring atmosphere, and to use small "elevators cabins" attached to robotic arms to go from the ships to the rings and vice-versa.
Another reason why it's not done is because one of the reasons why we have a space station is to do microgravity experiments, and having artificial gravity only hurts that.
That's what I thought until I started looking into it. The module has actually been built (several versions in fact), but never completed and launched.
It turned out during tests and simulations that the station's structural integrity was at risk and so it was decided not to attach a centrifuge to it.
Whether these concerns were warranted I cannot say, but engineers at NASA deemed it too risky to try.
https://blogs.scientificamerican.com/life-unbounded/watch-th...
We've also done some experiments already. There was, I believe, a Mercury mission where they spun the ship up. If I recall, it didn't go super well. But hey, we've had 50+ years to think of how to do it bette!
It’s don’t commonly on Earth. Most of the point of LEO space stations is to study microgravity so you wouldn’t even want it.
It is indeed pretty easy, but annoying to do for technical reasons (rotating joints, etc). Easier not to.
Basically, we would need to make something hundreds of meters in diameter to have any hope of a comfortable living situation. This is a huge amount of mass to get into space, which is notoriously expensive, but getting cheaper every year. Maybe one day we'll hit an inflection point where this is reasonable.
That would give you a circumference of around 628m. That sounds like a lot, but if you could build it in 80m segments by bolting each segment to the outside of SpaceX Starship (which is 120m tall) that would take 8 launches to get the ring in orbit. Plus some more launches for the hub and spokes and panels and everything else of course. Still, 15-20 launches is not outside of the realm of the feasible. If there were the political will (or personal fortune) to build this it could be done.
Split the initial station into two stations with a large number of cables connecting them securely. Now on your calculator, put in a 70m radius and a gravity of only 0.3g. All green dots.
But how do you get between the halves?" you ask? I think there's a simple answer to that: have cables complete the circle. A small car riding those cables can carry you around the radius. Then over time, you add more cells until the circle is complete!
The zipline would be trickier to make work, then. Probably you have a gadget that walks up the tether, and then you flip around and it walks down to the other end.
Not in my cosmic neighborhood.
If you instead make the rings "super-modules", you can connect as many as you like along a central axis of rotation. As long as the individual rings are balanced you're good to go. If they spin freely relative to each other, you could even build a super-modular ring in place and only spin it up after it is complete.
I'm pretty sure that phenomenon even kills the https://en.wikipedia.org/wiki/O%27Neill_cylinder, especially once you introduce liquids and soil to the interior. It's likely that we have to spin the cigar along the long axis to keep from killing everyone, which would greatly reduce the usable surface area and screw up the artificial lighting situation.
For modularity it might make more sense to use nesting. A building inside a building has no seams. Doors only need footpaths between them, not hard structures. The inner building can be used for shelter in case of an accident, and can be run at higher pressures than it could in hard vacuum.
In the tinker toy model you would tend to have to keep repurposing buildings because while the size may be appropriate, the older structures may get pushed farther and farther from the center of the action, rather than staying in the center of the action.
When we get into the more utilitarian phase of space development, then I think you would want something like shipyards where there really is a big micrometeorite shield (yes, as a sphere) with the inside filled with scaffolding. Robots scoot around do work with old and new hardware.
If you think about nesting ROTATING structure inside of other pressure-envelope structures, then you're getting into some really crazy stuff. Are there designs that might make sense? Maybe, I don't know, I guess I wrote a blog about it
Windows are at a huge premium on cruise ships. It'll be much worse on space ships. But it's possible that inside windows will eventually look out onto something more interesting than the black void of space, so an inside window may be preferable. One of the reasons we look out the window in a car or on a boat is to establish the horizon and fight motion sickness. If you look 'outside' of a rotating space station - especially a rotating space station orbiting a planet or moon - you'll head rapidly in the exact opposite direction.
I think my train of thought makes a bit more sense for moon and asteroid bases rather than free-floating orbital structures. And asteroid bases - on the right asteroids - are probably going to house most of the people.
The ISS design definitely doesn't scale up. Everything off axis is a lever arm and the bigger you make it the more the whole thing tries to twist itself apart.
Or, just extend everybody's cable a notch so there is room to shoehorn in the next pair of cans. As you add cans, the radius grows.
"Cans" is the only practical way to think of building a rotating station. Of course, the cans are really Starships, hanging by the nose. Passageways between cans are fabric tunnels. Each can has a mass on a column that is automatically raised and lowered as people and things move around, to maintain rotational stability, and keep the hub centered.
Realistically, you'd want to keep re-using the expensive parts of the starship rather than park them in space, which makes me wonder what's the best way to re-use a starship while leaving cylindrical body sections in space?
You could have a Starship body with sections that are removable -- like maybe you have a 50 foot section that unbolts from the nose and the tail which you leave in space, while the nose and tail get re-connected and return to Earth as a shorter version of Starship. Or maybe you could just launch two Starships, and in space remove the engine from one and place it inside the other as cargo, so you land one complete starship and the extra engine, but leave one complete body in space.
I doubt it's possible to have a disembodied engine land itself using its own thrust without a lot of clever and novel engineering, but maybe it can land by parachute? Or use thrust to slow its re-entry so it doesn't overheat, then parachute the rest of the way?
Maybe you vent the tanks and open a hatch on top, and there is a stairway inside with floors, ductwork, and places to clip on lights and electric outlets. Probably you roll out insulation onto the walls so you don't burn yourself or get frozen-stuck if you touch them, depending on what is going on outside.
Non-popularized version https://space.nss.org/settlement/nasa/75SummerStudy/Table_of... (but that was the very first study iirc and made some known mistakes; I have no idea what the state of knowledge is now.)
One, they had a significant impact on the science fiction that came after them. We see recapitulation of this imagery in a lot of '70s-'90s anime (less often in live action, which I attribute to cost to film it).
Two, I believe when we get anywhere near a technology level to try something like this, the result will look radically different. I'm reminded of the way that old depictions of the Earth from space rarely included the clouds, which are omnipresent and unavoidable when actually looking at the planet. Some things, a person just can't imagine until they're there.
Given the risk of random super high speed/energy collisions with space objects, I would wonder if a more resilliant craft shape might be based on something nested and self-simlar, literally, "bigger on the inside," or like a disconnected formation that isn't physically connected. An orbital craft in a relatively stable solar system that used a planet as a lower energy "mooring ball" might allow for simpler geometric craft forms, but there's probably a maximally optimal shape for deep space starfaring vehicles. (oumuamua was very oblong and cylindrical, which might be a hint).
Don't forget Gene Wolfe's marvelous The Book of the Long Sun!
If we’re stuck with rockets that either lift tiny payloads or are ludicrously expensive to launch (see SLS’ $2B-$4B estimated cost per launch), I think your predictions are right on the mark. In that situation building anything even remotely luxurious is not practical.
If we assume the existence of something like Starship+Superheavy as it’s currently planned, that starts to change. You’re still not going to see O’Neill cylinders, but simple ring stations with interiors nice enough to be resorts are within grasp.
To achieve things as fully as depicted in these images, extraction of resources and manufacturing in space will be necessary. Even with cheap superheavy launch, lifting all the required material to orbit isn’t a practical consideration. Achieving those prerequisites is helped quite a lot by Starship though, because it’s more than enough to bootstrap asteroid mining operations and the like.
I think we'll actually see more of similar designs, even if much smaller, e.g. in spacecrafts for human journeys beyond the Moon and, indeed, space stations.
Interestingly, many very recent Sci-Fi movies involving realistic-ish human space travel feature spacecrafts with spinning toroidal living quarters.
Some less recent ones too [1]. It never ceases to impress me that this was filmed before the moon landings.
It's feels strange to look back and think how much the world has changed since I was a child in the 1980s, and yet how little it changed in the ways I thought it would.
Elon estimates that the refueling procedure necessary for interplanetary starship missions would require 8 fuel tanker starship launches, but this could be cut in half if the tankers were stripped of the elements needed for reentry and landing.
I could see the economics working out to where it would make more sense to launch stripped down single use fuel tanker starships, and then sell the empty orbiting shells to someone interested in building in space.
https://caseyhandmer.wordpress.com/2021/11/17/science-upside....
I just meant to point out that a stripped down starship would consist of 30+ tons of easily weldable steel pre-fabricated into a reinforced pressure vessel. Spacex's interplanetary goals would benefit from treating the tanker starships as expendable, and if someone was inclined to start building habitations similar to those depicted in the link, they could buy up the building-blocks for a song.
Similar results can be reliably recreated on earth. Ultrasonic welding rubs two pieces of metal together until the oxide breaks apart leaving pure metal to fuse. Explosive welding creates a plasma that strips off the oxide layer, and then propels the metals into each other. This method has the benefit of bonding dissimilar metals, and usually produces bonds that are as strong as the weakest metal.
The main issue with welding in space is the lack of convection based cooling, which means the welds take longer to cool through conduction, which can result in a larger HAZ. Increasing the mass and heat capacity of the adjacent material greatly reduces this.
The lack of an atmosphere and contaminants makes space a near ideal welding environment.
For all its issues, Earth is actually pretty resilient. To ability to destroy civilization is pretty much limited to very large nation states.
Not so in a spinning space colony. A small group could easily destroy it. Thus, there will be ubiquitous surveillance and huge social and legal pressure towards "correct" behavior.
By the way, I've done the math, and a habitat like the one in that book would need to fuse 18 metric tons of Deuterium per day to produce "solar light" for an area equals to Virginia state's. Pumping heat out of that thing must be a similarly hairy challenge.
Regardless, by the time we're creating massive space colonies we'll probably be manufacturing oxygen rather than maintaining massive forests.
What's the difference?
Unless you're playing devil's advocate, I'd say you are shilling for a certain industry
Btw, photosynthesis doesn’t produce CO not because it’s more efficient. It doesn’t split CO2 at all, it does CO2+water+light+catalyzers -> carbonhydrates+O2, and this O2 comes from water, CO2 goes to carbs as is.
Of course CO could also be used to make some kind of carbon compounds: https://www.scientificamerican.com/article/splitting-carbon-...
Great Mambo Chicken and the Transhuman Condition by Ed Regis
It includes a great section on space travel and space living.
https://en.wikipedia.org/wiki/Great_Mambo_Chicken_and_the_Tr...
https://www.amazon.com/Great-Mambo-Chicken-Transhuman-Condit...
I loved those books!
By chance does anyone know what they might have been?
https://www.worldcat.org/title/high-frontier-human-colonies-...
https://www.worldcat.org/title/colonies-in-space-a-comprehen...
Pricing on Amazon for new copies seems to be a little fucked, but there are several used copies available for reasonable prices.
NASA SP-413
Space Settlements: A Design Study
Edited by Richard D. Johnson, NASA Ames Research Center, and Charles Holbrow, Colgate University
NASA Scientific and Technical Information Office, 1977
http://large.stanford.edu/courses/2016/ph240/martelaro2/docs...
But instead of O'Neill cylinders he seems to be spending his money mostly on lawyers.
I really want to hear from anyone that disagrees because there's got to be something I'm missing. Ultimately we probably just need to do some testing.
All in all though, what NASA really needed to make this stuff real was what SpaceX is working to provide, sending tonnage into orbit at an economic price.
Something similar is depicted in the film 'Elysium'. But it is a open torus, rather than a closed cylinder and they never explain how they keep the atmosphere in.
In fact, starting with 0080 war in the pocket isn't a bad idea given the self contained story.
From there, I'd check out 0083: Stardust memory and move on to the Zeta Gundam tv show.
Then, for a completely different experience, you can check out the alternate universe shows like Mobile Fighter G Gundam or After War Report Gundam X
https://colonydrop.podbean.com/e/space-colonies/
For actual in-depth scientific exploration of the colonies of Gundam, Dyar Straights is pretty great:
How tall do atmosphere retaining walls on rotating space habitats need to be?
https://worldbuilding.stackexchange.com/questions/119739/how...
It doesn't matter what frictionless calculations say, the air will climb through any wall you create until it gets out of the station.
According to the stackoverflow entry above, a 10km high wall on a ringworld would leak about half the atmosphere every century.
Obviously the wall would have to be airtight.
You might be able to slow down the loss of gas by putting lips on the tops of the walls and maybe even air jets blowing downward though. Or leave it mostly closed except for a few openings for spacecraft to enter or leave. Also, working out the practical considerations for a Ringworld is an exercise in futility anyway. You are already well beyond practical when you start building one.
Yeah, with constant gravity and no friction.
100km isn't enough because no height is ever enough, because friction exists. Any wall will have a flow of air near it going away into space, as a result, the pressure will fall much slower than exponentially.
Yes. So you would need to build it multiple of 10km. Assuming the pressure falls of 75% for each 10km (which seems about right from a quick glance at some tables), if it was 100km high the loss would be 0.25^10 of what it would be at 10km. So 100km wall would be ~million times less loss than a 10km wall.
The gravity would be constant if the rotation was constant. No sure what you mean by 'no friction'. Friction against the wall?
Hum... No. The gravity reduces linearly with height.
And yes, friction against the wall.
I'm not convinced friction with the wall is going to result in any additional air loss. There is no 'upward' (towards the top of the wall) force component.
Friction ensures that whatever air reaches a high altitude near a wall tends to stay at that altitude and spread again on the lower gravity. The difference in pressure between this higher place and a lower one bias the movement up, there is no upward force component on the dynamics of any few components you can choose, it's emergent.
not familiar with the design, is there gravity? that’s why our atmosphere sticks around, right?
And even if their atmosphere wasn't lost, the inhabitants would quickly suffocate and die due to low air pressure. On Earth, there's 10 tonnes of atmosphere pushing down on every square meter at sea level, compressing the air to 1 bar. Reduce that ~100 km column of air to ~100 m, and the pressure would be very much lower.
The main advantage of open air designs is it allows you to use aerobreaking when approaching the habitat which could be a significant save in fuel.
One possible solution is to ionise the air near the walls and then use a magnetic field to contain it. This would not really prevent all air leakage but you don't really have to as long as it's substantially reduced since even the relatively diminutive size of the Elysium habitat would contain a fairly formidable volume of air. There can also be outside magnets that can arrest the momentum of the escaped ionised air enough so it falls back down to Earth. Then all you need is a tether extending down to the atmosphere with an internal air pump and you have a self contained cycle.
[^1] https://2warpstoneptune.com/2014/03/04/usborne-publishing-th...
[^2] https://www.murrayewing.co.uk/mewsings/2011/04/17/the-usborn...
But without space to live, grow, and try new things, our humanity is maimed. The path of least losing is leaving the planet alone, and making our own habitats.
It would be way easier and cheaper to build one unrolled out onto an actual desert. And safer. Maybe try that first?
You can stay in the guest rooms at Arcosanti, the city he started building in the 70s, it’s wonderful having a glass wall looking out to the barren desert, knowing i can walk 5 minutes up the path to a whole “city” of a cafe, theater, and workshops.
What you say is true but with a couple of caveats.
1. Yes it would likely be cheaper to build domed habitats in the desert. But how long will that be the case? In the desert you have to build on top of sand (or dig way down and build a crazy foundation that would likely cost close to a space habitat) and there may be local governments who aren’t keen on random immigrants coming and building giant domes in their territory.
2. Humans have lived on Earth for a hundred thousand years and have barely colonized the most extreme deserts (both frozen and unfrozen.) The reason thus far is because there isn’t a good economic reason to do so. We’re talking about colonizing the solar system, for resources or whatever, so the idea is that colonizing the desert isn’t sufficient.
3. Space is empty right now so we have to bring everything up from the surface. In a future where people have an economic need to colonize Mars it would make sense to have infrastructure in space that allows for mining/etc so that you don’t need to lift 100% of the resources off the planet. In which case, and with decent automation, it may become cheaper to build habitats in space than it is to build buildings on Earth. If it’s early and there is no infrastructure in space there likely isn’t an economic need and thus those who lived there would be doing so for their own pleasure and would pay a premium.
To clarify: My argument isn’t that we should build these habitats or we should colonize anywhere at all. But if people are wanting to colonize Mars it would be cheaper and nicer just to build rotating habitats with Earth like gravity and whatever weather you choose. I know if worked on Mars I’d prefer to live in a sunny paradise orbiting it than live below the surface while only having 1/3 gravity.
If we were really serious about this we would have a followup to the Biosphere projects that finally solved the issues they identified. We should have several fully self contained habitats on Earth before we consider building them in orbit or on another planet. People are trying to skip all the way to the end without doing all of the hard work in the middle. It's doomed to failure.
So, pick such a place, and try it there first. If you aren't even talking about that, you are far from ready to make a go at someplace massively more hostile to your very existence.
I mostly agree, with a single caveat: there are (and never were) any benign species. There are only insufficiently capable ones.
I’m still bitterly disappointed that the timeline it proposed was not accurate.
Check out the amazing cassette futurism illustrations:
https://duckduckgo.com/?q=usborne+book+of+the+future&t=iphon...
They still seem to be making some of the best non-fiction kids books, my kids have some great ones.
Signed, former NASA guy, unpopular with the spacecraft engineering crowd
P.S. Yes, I know; Simpsons did it.
All I got was confusing USB cabling and Zoom that has problems detecting my camera and sound.
(Sorry I've been readying The Expanse series too much and it's making me very pedantic about spin gravity)
Instead, you'd probably want either a non-curved structure, or a flat false floor inside of it that is perpendicular to the direction of gravity. That would probably work ok though, since it would give you an easy place to run e.g. cabling, air handling, fluids, etc.
I mean, lots of people live on slopes here on Earth. It's actually a pretty desirable terrain, as long as you're not farming it. You can see in many of the toroidal stations that the hillsides are terraced and treated like slopes.
The direction of gravity won't be perpendicular to the curvature of the hull, but who says you need to stick to the hull? Even on Earth, people don't stand diagonally on hillsides. We build stairs, towers, and terraced gardens, with man-made floors perpendicular to the direction of gravity.
Some of the illustrations are more realistic than others in this respect.
The idea of mirror flaps swinging around as the cylinder rotated was ridiculed, and brilliantly replaced with the Mitsubishi Dragonscale Mirror Array, a cone of millions of individually-steered mirrors. Clever re-uses of that drove major plot points both as a weapon, a la Archimedean defense against ships, then as the light pump for a beam weapon, which then became remote power for vapor-phase asteroid ore refinement, and then for a capital ship, all background for solar-system-scale political intrigue.
There are many experiments of various types of organisms in space but I’m not aware of any that test and try to sustain entire ecosystems, something that’s essential for prolonged human life off of this planet.
Improvements in space life support technology should have significant and positive applications on Earth as well.
You can even buy them [1].
[0] https://www.dailymail.co.uk/sciencetech/article-2267504/The-...
It might be the only book that's ever given me the feeling of agoraphobia with some of the descriptions. I'd love to see some kind of adaptation, but it's not sure if a TV screen could ever do justice to the scale.
Looking at what the past thought space exploration would become is really fun. Disney and Wernher Von Braun collaborated to make a happily imaginative view into space exploration back in 1955.
I miss those days.
Super funny, and very relatable, if you're a creator or engineer.
And the idea is to lower the cost of all the various technologies required and then operate and build them cheaply using extraterrestrial materials without any more continued reliance on Earth’s resources. NASA was supporting this idea of asteroid mining (for in-space use) at one point with the Asteroid Redirect Mission (ARRM) which was canceled and replaced with Artemis.
Someone should do an open world game that took place in one of these.
A good example is Larry Niven's Ringworld. It's a cool idea in the early days when people were thinking about mass-to-living-area ratio but to produce Earth-like gravity at an Earth-like distance would require the thing to spin at (IIRC) ~1.5m km/h. The centrifugal force would tear that apart.
Likewise, people mistakenly view a Dyson Sphere as a rigid shell around a star. That was never the concept. This misconception is so common it's led to the term Dyson Swarm, which was always the original intent: a "cloud" of orbitals around a star all moving independently.
The likely future of space habitation is (IMHO) going to use the humble O'Neil Cylinder [1]. This is nothing more than a cylinder a few miles wide and maybe a couple of dozen long. Such a cylinder could potentially house millions. They're large enough such that spin gravity wouldn't be disorienting and small enough such that they don't require exotic materials (eg space elevators for Earth require exotic materials we haven't even theorized yet other than possibly graphene).
So an O'Neil cylinder can be built of nothing more sophisticated than stainless steel.
You have options of joining them to other cylinders. You can build a "ladder", which is a series of orbitals all in the same orbit but slightly displaced. You could even run cables for transportation between them. You could construct networks of these things.
You put solar cells on the outside and a window at one end, possibly using refractive materials down the center to create more pleasing diffuse light and the whole thing is reasonably low tech and low maintenance.
You could even build them by hollowing out asteroids and other space bodies.
The mac daddy to the O'Neil Cylinder is the McKendree Cylinder [2]. Instead of being a few miles wide, it might be hundreds of miles wide and much longer. This is beyond the tensile strength of stainless steel but within the theorized limits of graphene.
Such a cylinder could comfortably house billions of people.
As much as it's cool to have things like the micro-gee environment of the ISS, I honestly wish we'd start building prototypes for spin gravity. This would greatly simplify living in such an environment for extended period of time.
To give you an idea of how efficient thing is for living area, IIRC the estimate is about 1% of the mass of Mercury could consume essentially be a complete Dyson Swarm around the Sun and comfortably house a quintillion (10^15) people.
Planets are nice and all but are horribly inefficient uses of mass to create living area and come with some serious negatives, not the least of which is the energy cost of entering and leaving such a gravity well.
This is also why looking for the signature of such a Dyson Swarm as evidence of extraterrestrial spacefaring life makes way more sense than pretty much any other approach. Saying that we're less than 1000 years away from having this kind of space-industry is beyond conservative. 1000 years ago we were throwing spears at each other.