What those vertical subway cars might be like is a good question. To increase capacity, you could make them tall, with multiple decks serving multiple floors, I suppose. You could make them wider, but that would take up floor space on each level.
You hooked me. I’ve been doing calculations in my head, so now I’m going to inflict them on all of you.
A space elevator’s terminus has to sit in geosynchronous orbit. That’s 22,236 mi according to the first cite I grabbed, or 117,406,080 feet. Since a floor is about 12 ft, including space for cables and plumbing and such, that would be 9,783,840 floors.
With a station every 20 floors, you’d need 489,192 stations. I hope you run a contest to give each of them names.
But that also makes each station only 240 feet apart. That’s ridiculously far for an elevator stop (what would people have to do, use stairs to go up or down 10 floors) but ridiculously close for a subway stop (it can’t pick up any speed because the period of acceleration is too short). You either need subsidiary elevators to go the short distances or a secondary short haul system - IOW, exactly the problem you already get on a 1000 ft skyscraper, except multiplied 117,406 times. The speed of getting anywhere outside your block is another issue. The fastest elevator is currently around 40 mph. That means it would take 556 hours or 23 days to reach orbit. True, that’s 17,600 floors per hour but that doesn’t get you out of your immediate neighborhood. You couldn’t get up to this speed with stations that close, now could you keep that average speed while needing to make stops at intermediate stations.
All of that is pure number play. The bigger question is why anyone would want to live on 4,576,876th floor of this structure? What conceivable rationale would there be? Imagine everyone on earth living in a band 20 feet wide along the equator, with no way to go outside. Other than the making of a bad sf story, how can a society function in such a space?
A space elevator is a fascinating structure, but its only real purpose is to get stuff into space without a million gallons of rocket fuel. Housing along it is more than unreasonable; as Lumpy noted it’s probably destructive and even if physically possible an economic and societal nightmare.
Actually, I was thinking of the Mile-High Building, not the space elevator. The space elevator would be of a completely-different scale.
I read an SF story a while back, I think it was one of the 2001 sequels, where the protagonist awakens in a tower structure built around a space elevator. It is old and enormous, but even after centuries of construction for varying purposes, 99 percent of the tower is skeletal or unbuilt.
Yes, but if it can be done, then the answer to the OP’s question is there is no limit. (Except I guess it could prove difficult to extend it forever into space.)
You ask about the practical, economically useful limit—as opposed to the physical limit.
The sweet spot will vary some depending on local building codes (how many separate exit stairs are required), elevator codes (Asians will more readily pack themselves into full elevators), and construction costs vs. land values. In Chicago the sweet spot is currently between 35 and 50 floors for residential buildings. Higher than that—unless you can offer world-class premium price views—you’re eating up more in floor space with the additional elevators than the extra floors will bring you.
For office buildings, the calculation also has to include the timing. You need to sign up a couple of big anchor tenants (taking 15 to 20 percent of the space) to get your financing, but they’ll seldom sign a lease more than 30 months out. So you need to deliver the building pretty quickly, and that sweet spot seems to be about 1 million square feet, again in about 50 stories.
As we saw also on 9/11 the taller the building the more prone it is to have airplanes run into it.
And then what if there is a fire or even a bunch of injuries or sick people on say the 110th floor? How to get emergency crews there?
If the building is a mile high, it will be big enough to support its own emergency services halfway up.
I still think plumbing is going to be an issue.
It always has seemed to me that the practical limit is “fear”. Not many folks are going to want to work a mile in the sky. And what’s the point of having a building so tall that most people won’t even go to the upper floors?
There’s no economical way to have all emergency services on call in house 24 hours a day for such a limited population and rare emergencies.
That’s just one in a long list of reasons why such buildings are impractical. As was mentioned before, people are going to have to live, work, and shop in the same building, only venturing out on special occasions (holidays & such) because just getting down to the ground floor would be too much of a logistical hurdle. The elevator ride to the top floor would probably take an hour or two, in addition to whatever travel time would be required to get to the building itself. That means you’ll need to have seats, and possibly TV or some other form of entertainment. The elevators would be more like waiting rooms than any elevator we’re used to using today.
If you have thousands of people trying to get up & down the mile-high building every day (commuting to work & back), then the logistics become impossible. If you try to have enough elevators to accomodate all of these people, then there won’t be any room for anything else in the building. So, no, they’re going to have to live up there, and shop up there, in addition to working up there. It’s pretty much like living on a space station.
No place on Earth has a population density high enough to make a mile-high building practical. Not even Hong Kong. It would be a pure vanity project.
To make this work, you have to have the buildings interconnected horizontally as well as vertically. Instead of 1 single supertower, you need a network of dozens of supertowers. You’d use elevator lobbies, and have skybridges or even automated horizontal elevator cars interconnecting the towers at each elevator lobby level (which might be every 30 -50 floors or so)
If you have a network of towers, this also takes pressure off the elevator problem. For one thing, it means that you have more places to go. With a network, you could have dozens of stores and restaurants and workplaces distributed throughout the towers. There could be several elementary schools (competing with one another for tuition/school vouchers!), a high school or 2, maybe even a university.
Instead of just a few employers, there would be hundreds - in principle, a big enough pool that most workers could find a job and most employers could find the workers they need from among the tower network residents.
Also, to get to the ground floor, there could be an express elevator to the ground floor located in each elevator lobby. So the actual way you get to the ground floor is you choose a local elevator to get you to the nearest elevator lobby (within 30-50 floors) and then you choose an express elevator to the ground from there.
All this can work. There are nasty problems, such as the stair one. Those stairs are non-rentable space, they are too slow to really evacuate quickly anyways, and so on.
The reason we don’t see these yet is for 2 reasons. One is that current construction techniques make building towers very expensive. The other is the http://en.wikipedia.org/wiki/Network_effect
Until you have enough towers built and interconnected, the “arcology” idea won’t work. So any project that doesn’t have enough towers will fail. But, these failures will mean that decision makers are unlikely to approve a large enough investment to make a network of towers that actually works.
Basically, on opening day you have enough towers and infrastructure that it’s basically a prebuilt medium sized city, just waiting for workers and businesses to move in. There would be significant advantages. EMTs and police would get elevator overrides, such that their response time would be under 5 minutes. You would have total control of the population - bad in a dystopia, but it also means 0 homeless and perfect surveillance of everyone, so crime would be very rare. (since there would be cameras in all corridors and elevators, so it would be very difficult to commit any sort of crime and not be caught)
Also, individuals entering the tower network could be given a badge, and physically prevented from going anywhere they aren’t allowed.
You could have an enormous deal of collaboration between businesses and even schools, due to the minimal transit times. Work out a deal to share development expenses on new technology with another business? You can walk to that business in about 5-10 minutes. Got an outsource firm creating a project for you? Check on their progress in person. And so on. I’m imagining a building full of high technology businesses, all robotics firms and software development houses and remote factory plant operators. Everyone sorta leverages off each other. If a particular skill is needed, someone could just go learn it at the local university, a 5-10 minute walk away, and be back for work after class.
Since there’s no motor vehicles, everything could be powered with mostly solar. Most physical labor would be done by robots - some in the building network, and then whole factories full of them located miles away, on the polluting side of town.
We already have this: they’re called streets. You can’t make economic sense out of duplicating a street, even in miniature form, dozens of times. Lots of cities have skybridges or tunnel connectors between a large number of buildings. They are expensive and require ridiculously high traffic volumes. And when you do get people to use them, they have an effect on street level traffic, as downtown Minneapolis saw as street level shops failed when people stopped going outside in winter. Trying to extrapolate this into multiple connectors is utopian thinking. They will never all function equally in the way needed.
You recognize the problem that a network of super-buildings can only work with a critically large population, so getting there is next to impossible, but you make the additional assumption that such a conglomeration will be totally self-supporting because everything everybody can want is present. That’s never happened in reality and there are good reasons to expect that it can’t happen even in theory. That’s not the way economies or people work. They function in hive terms only in science fiction stories, which is exactly what you’ve written.
I was once seduced by their attraction myself, until I started actually studying urban design. Man, that’s humbling, both for the slap of reality and the spectre of so many supposedly bright people who keep falling for the same fallacies of what people *should *want and *should *do. You know how far packing people into high-rise cities goes back? 1894. Metropolis long before Superman.
According to this site, your could theoretically build a steel skyscraper over 6 miles high. That’s just based on material strength. It doesn’t take into account economics, construction methods or practicality. Remember that modern skyscrapers are mostly empty glass boxes of air anyway.
Obviously as you start building taller and taller, you get into a whole lot of practical considerations:
-Elevators - I’m not an elevator expert, but I suspect that there is a maximum practical length for the cables. There is also the matter of elevators having a maximum practical acceleration (IOW, you don’t want the passengers hurled against the floor or free-falling through the car).
-Construction techniques - I suspect that building a skyscraper a mile or more in height would require the development on new techniques to be done safely.
-Economics - Who is going to fill up all the floors? One World Trade Center in NYC only has a 40% occupancy rate right now. And what is the point of building a half mile high tall skyscraper in the desert instead of 5 smaller skyscrapers? It’s not like land is in short supply
I’ve also heard that the wind hitting the tower will cause it to sway slightly. On higher floors this sway is more significant, so you would get people on upper floors getting “seasick” from the slight motion.
Hell, the water in my mom’s 11 story seaside condo building toilet will, during high winds, slosh around pretty vigorously…
Something that hasn’t been mentioned yet: where is the food for all of these people going to come from? You’re going to have to ship it in from outside, along with everything else that these people need (which, realistically, will be most things). The tower won’t be self-sufficient; it will really be more of a “company town”, with the building’s owners controlling every aspect of the inhabitant’s life: work, living space, shopping, recreation. Historically, company towns have always turned out to be rather dystopian, with the workers ending up as economic slaves.
That was 3001: The Final Odyssey. Clarke seemed to feel the main benefit of such a system was that everybody could decide how many G’s to live in-- IIRC the protagonist lived at the 0.5G level of the tower. Living on the ground, the full 1G, is seen as kind of eccentric.
Seriously. Whenever someone advocates these self-contained multi-use “archologies”, I don’t think of utopias. I think of the Tyrell Corporation building from Blade Runner or the Megacity blocks from Judge Dredd. The problem that always comes to mind is that you are trying jam a self-contained city of thousands of people into a single structure. Unlike an organic city layout, the archology can’t expand, contract or easily rezone to meet the demands of the residents and workers. It’s very easy to imagine one of these things getting thrown out of balance. Becoming underpopulated or overpopulated to the point where critical services were no longer economically viable, starting a vicious cycle and ultimately becoming an dangerous overcrowded (or vacant), dirty slum.
All tall buildings sway slightly, but they tend to be designed so as not to make the occupants uncomfortable.
Or a giant paternoster lift. Just step on and step off at the right floor. My old university Arts building has one. YouTube link: http://www.youtube.com/watch?v=w8-RdjCll0w 
A 300-storey paternoster might be fun…