Could Coruscant (or something like it) be possible?

[cantab]

Ah, neat find. So on a planet with Earthlike gravity and temperature the atmospheric pressure could be suitable for humans over about 40,000 feet or 12 km vertically. With a warmer climate or lower gravity it would increase. Coruscant is probably close to that then. It may indeed be why the buildings aren't taller.

[JDCollie]

Realistically, with sufficient technology of course it would be possible. If you put enough resources in, then a closed system can be created assuming you have 100% efficiency, and also assuming that the biosphere is completely artificially regulated (like I said, sufficient technology.) Then real question is if it would be possible to do without importing massive amounts of biomatter and water first.

[hawkinator]

One idea I thought of is that maybe in addition yo rich / poor distribution being by altitude, it might be by latitude, with equatorial regions being richer (daylight longer, cheaper access to space travel) and polar regions being where the poor folks live.

[cantab]

I doubt getting into space is much of an issue, Star Wars ships probably have millions of m/s of delta-V before you even consider the hyperdrive, the few hundred from the planet's rotation will be moot.

[hawkinator]

True, but length of daylight and climate could certainly have an effect. Of course, if we were using more realistic space travel, delta v would be important. Which brings up another question, how would they move around without super flying cars? I'm imagining a world of monorails, hyperloops, maglevs, and the like, with helicopters and maybe airships for those who could afford them.

[Idobox]

With the kind of density a city-planet would have, rail is by far the best option. If you have time, you can the number of daily rail users vs density of urban areas, and you'll see the trend is very clear.

Vactrains and maglev are good at one thing: long distance travel. But in a city with 5000 levels, you would rarely need to move more than a few km to find what you're looking for, and you wouldn't have time to accelerate, and the bulk of transportation would be done in relatively slow moving vehicles.

[Nuke]

you are going to need a combination of high speed and low speed lines. its a planet size city, if you happen to need to go to the other side of the planet, then a vactrain is exactly what you need. building of runways is going to be a prohibitively expensive use of the land, so air travel would be limited and also not very safe. if planes crash, and they do, its always going to be into densely populated areas, and that should be avoided. smaller vtols are probibly going to be used for police, fire, medivac and buisness uses mostly.

general travel would best utilize vactrains. i imagine a system where you can drive your vehicle right onto a vactrain module, which gets loaded into the system and stops at stations every few hundred kilometers. some might be express routes to travel longer distances without all the stop and go. you could also theoretically drive anywhere on the low speed system, and the vactrains are just a means of saving time. you certainly wouldn't want a 4 hour commute.

you might even dispense with personal vehicles all together and use a mass transit system on a planetary scale. again using a combination of high and low speed tubes. rather than having large trains, you can have smaller cars which can be called at a station. you punch in your destination and it will find the fastest route for you, working kind of like a big packet switched network. you might get routed through the high speed system if your destination is far away. you just sit and enjoy the ride. in theory you could go pretty much anywhere on the planet in a couple hours.

[NGTOne]

you might even dispense with personal vehicles all together and use a mass transit system on a planetary scale. again using a combination of high and low speed tubes. rather than having large trains, you can have smaller cars which can be called at a station. you punch in your destination and it will find the fastest route for you, working kind of like a big packet switched network. you might get routed through the high speed system if your destination is far away. you just sit and enjoy the ride. in theory you could go pretty much anywhere on the planet in a couple hours.

This is actually a really cool idea, and I think it's been proposed in some plans for arcologies/future cities. Problem is, the infrastructure cost for a system like that is massive - the reason packet switching works is because it's purely electronic, which means that actually redirecting a packet costs nothing. Imagine having, say, a rail switch that has to move several hundred thousand times per day, and scale that up to the size of a planet. You'd need either a) something far beyond today's technology in terms of both materials science and computational power (as mentioned before, this can be handwaved by pointing to the setting), or an army of maintenance men and a massively redundant network, and likely both. To truly serve everybody, you'd likely need a boarding station every few hundred meters (beyond that, people start being less likely to want to ride transit and just want to drive - this is part of why bus ridership is always so low in the suburbs of today's larger cities [even ones with well-developed transit systems], because only people who really need to will bother to walk out to the bus stop).

It's still definitely a really cool idea, though.

[cantab]

I think long-distance travel would still be air. The runways could be elevated over the city, or even built into the megastructures with more living space over them.

Of course it's also very possible that virtual reality would mean physical passenger transit is fairly rare anyway. You'd still need to move freight but that could be much more rigid and structured.

[vger]

I agree with both answers provided.

As for food:

If energy is no problem you could have giant hydroponic farms ... maybe in underground caves with huge artificial lightsources that imitate the stars spectrum.

A bigger problem IMHO is waste processing and water.

A city the size of a planet will need huge amounts of water .... its inhabitants will also create huge amounts of excrements.

If we want to have a Coruscant that is self sustainable to a large degree, we would definiely need methods of waste recycling that are close to 100% efficient.

Escpecially with regards to the water recovered. Else Coruscant would always be dependant on a huge fleet of waste collector ships (to ship waste off world) as well as ice ships (to bring in new water)

I don't think we could construct a pumping system for the water, no matter how much power we had for the task. Or it would require an entirely new method of moving water. Pumping water up a mile or more just isn't feasible. The amount of weight that would amount to, even if you were sucking it through a straw, would be ridiculous.

As for the waste... sadly this was one of my gripes about Coruscant in the films. That planet isn't as bright and shiny as it likes to make people think it is. But you wouldn't know that without going down to the surface where the sun never shines, about 2 or 3 miles below the sparkly skyline. The ground level is literally a cesspool of crime and scavengers and waste management is a way of life. It's exactly as glamorous as it sounds.

[Nuke]

This is actually a really cool idea, and I think it's been proposed in some plans for arcologies/future cities. Problem is, the infrastructure cost for a system like that is massive - the reason packet switching works is because it's purely electronic, which means that actually redirecting a packet costs nothing. Imagine having, say, a rail switch that has to move several hundred thousand times per day, and scale that up to the size of a planet. You'd need either a) something far beyond today's technology in terms of both materials science and computational power (as mentioned before, this can be handwaved by pointing to the setting), or an army of maintenance men and a massively redundant network, and likely both. To truly serve everybody, you'd likely need a boarding station every few hundred meters (beyond that, people start being less likely to want to ride transit and just want to drive - this is part of why bus ridership is always so low in the suburbs of today's larger cities [even ones with well-developed transit systems], because only people who really need to will bother to walk out to the bus stop).

It's still definitely a really cool idea, though.

i like to think of it as an engineering problem. a mechanical switch to move a car from one tube to another tube would be very complex. but you see modern rail yards with with complex arrays of rail switches that can accomplish the job, all be it in more or less 2d and using a lot of land area. you might draw other parallels with highway systems, or pneumatic tube transport in large buildings. automated factories are another good example of how computers can control complex events with absolute precision. analogies with packet switching networks are just analogies, but similar protocols for managing one can be used for the other, despite being carried out through mechanical rather than electrical means. so its not like we dont know how to engineer these kinds of things.

your basic unit is an intersection between 2 perpendicular 2 way lines. by default they never intersect, like an overpass. you dont want to change velocity while in the main lines. you need a system to take a car out of the main tube, decelerate, turn, accelerate, and rejoin the desired main line (and this might be a good place for a transit station as well). this all has to be done without interrupting traffic or endangering its safety. how its done also depends on the technology used. maglev trains might use magnetics to switch from one tube or another. you might use aerodynamic forces if you are in a low pressure tube, but this wouldn't work in a vacuum tube. the size of the interchange also depends on the speed of the main lines. the faster the cars move, the longer the acceleration/deceleration tubes need to be and the bigger the interchange structure needs to be. of course i would engineer this as part of the urban substructure, you might have a large building on top of the interchange to maximize land usage.

grid topology works best, you have a large array of fairly simple interchanges connecting intersecting lines. if one interchange is down for maintenance, you can use the next one. you might also have high speed<->low speed interchanges for the global lines. hub and spoke topology would be a nightmarish mash of tubes everywhere, and very complicated hub stations, loosing one of which would cripple or at least slow down a large number of routes. your tubes need to be smart. they need to be able to sense traffic patterns and usage. if one tube is congested, it might switch some of its traffic to another tube. the shortest route might not always be direct because of queues at interchanges, congested tubes that would be unsafe to add additional traffic, or perhaps you would need to bypass too many interchanges because of maintenance.

there is a catch though. its going to be astronomically expensive and very complex to do a planet wide transit system. it would likely be the greatest feat of urban planning ever attempted. even doing one on a typical urban scale without the super high speed lines would be difficult.

Edited August 31, 2014 by Nuke

[NERVAfan]

I don't know what Coruscant's population density is supposed to be, but I think you could get "sparse city" population densities over a whole planet to work (without importing food) with algae farms and such, especially given genetic engineering.

If all photosynthesis on Earth was used directly to produce human food (and everyone was vegetarian) you could get enormous numbers of people. This would also provide oxygen for everyone.

And there is probably room for genetic engineering to increase the efficiency of photosynthesis (which is quite low).

It wouldn't be a planet with literally nothing but skyscrapers, but it could be pretty dense.

I don't know how much of the problem the heat would be... but you could build it on a planet that started out cold. It would totally destroy the existing ecosystem though.

EDIT: I think the heat could be gotten around because the population I'm suggesting would probably be in the hundreds of billions range (which is likely less than Coruscant) and because this civilization would probably use much less energy per person for living needs than, say, the US. The algae is grown by sunlight, not artificial lighting, and there probably aren't actually mega-skyscrapers, which are a transportation problem -- the population density wouldn't be high enough to require them.

Edited August 31, 2014 by NERVAfan

[Idobox]

This is actually a really cool idea, and I think it's been proposed in some plans for arcologies/future cities. Problem is, the infrastructure cost for a system like that is massive - the reason packet switching works is because it's purely electronic, which means that actually redirecting a packet costs nothing. Imagine having, say, a rail switch that has to move several hundred thousand times per day, and scale that up to the size of a planet. You'd need either a) something far beyond today's technology in terms of both materials science and computational power (as mentioned before, this can be handwaved by pointing to the setting), or an army of maintenance men and a massively redundant network, and likely both. To truly serve everybody, you'd likely need a boarding station every few hundred meters (beyond that, people start being less likely to want to ride transit and just want to drive - this is part of why bus ridership is always so low in the suburbs of today's larger cities [even ones with well-developed transit systems], because only people who really need to will bother to walk out to the bus stop).

It's still definitely a really cool idea, though.

Maglev switches can be build without moving parts. If you are using a scheme like the magnetic river, or null flux loops, you just need to electricaly open loops to make them "disappear", and this can be done with solid state or vacuum devices (Vacuum switches are excellent for high power applications).

Maglev also has much less wear, making it a very good option for high density networks, even at low speeds.