5 ms·

Ask HN: Why is the tallest manmade structure only 2,722 feet?

6 points by a3voices 12y ago

I don't get why nobody built a simple tower with a narrow base to best that. Is it really that hard to do, or that expensive? Why aren't there any 10,000 foot towers?

dekhn 12y ago
ask yourself, why do you need a taller building, and if so, are you sure you want to spend the money to engineer it?
VLM 12y ago
Assuming you want a serious answer, a very HN one is to discuss scalability, and unlike rope or cables or fiber, towers most certainly do NOT scale merely linearly with length. Its way, way worse. Or if you prefer to think of it this way, we don't have enough income inequality and/or world wide wealth for one plot of land to "deserve" a 10 kilofoot tower. Another fun term to google for is Euler and column buckling. That's why we don't have 75000 foot tall radio towers, which at least superficially would seem to be a great idea that could get past the scaling costs because potential revenue would scale even better with surface area within line of sight. Or even more interesting a 75 kilofoot rocket launching tower so you could use higher Isp vacuum rated nozzles at launch (if you tried that at ground level they'd buckle from the outside in)
zachlipton 12y ago
Elevators. I mean obviously there are significant structural concerns as well, but elevators are a big part of what makes building super-tall buildings uneconomic and impractical. The Elevator Conundrum, as Wikipedia dubs it (https://en.wikipedia.org/wiki/Skyscraper_design_and_construction#The_elevator_conundrum https://en.wikipedia.org/wiki/Skyscraper_design_and_construc...), means that as you build a taller building, you need more elevators to service the floors. More elevators take up more space, meaning less rentable space for occupants. While skylobbies, double-deck elevators, and other tricks can help, they don't eliminate the problem, especially since no one is willing to transfer elevators four times to get up/down. We also run into the issue of how to build a 10,000 foot elevator, which is so far outside the competence of manufacturers that it would represent a huge risk to the completion of the entire building project. I am, of course, assuming you plan to build a useful tall building instead of an empty 10,000 foot tall shell for no particular reason.
- Pyrodogg 12y ago
  The elevator problem is partially solved by never leaving your section of the mega tower! Work on level 120 Sleep on 73 Recreation on 145 Skyway connections to neighboring mega towers every 50-75 levels. Actually travelling to the surface world would be akin to driving for hours across the state. It's a trip and would be planned for accordingly, and happen rarely.
  - 27182818284 12y ago
    >Actually travelling to the surface world would be akin to driving for hours across the state. It's a trip and would be planned for accordingly, and happen rarely. I must be missing something. 10,000ft is 1.8ish miles. That's like an 8 minute bike ride not a cross-state drive. Even if it took 30 minutes by elevator, that's a reasonable commute in cities like Chicago.
    - Pyrodogg 12y ago
      Yea, I went funny with the scale. Jumped straight from skycraper to something the size of a GSV from the Culture series.
- jvvlimme 12y ago
  The main problem with elevators today is that you can only have on cage per shaft. You could solve this if you could have multiple cages per shaft. A bit like how trains operate with switches and passing points. I imagine that would take some serious technical development but doesn't seem entirely out of this world. It would be easier if you have cableless lifts like the maglev lift Toshiba developed (http://www.toshiba-elevator.co.jp/elv/infoeng/technology/tec05.jsp http://www.toshiba-elevator.co.jp/elv/infoeng/technology/tec...).
  - JoeAltmaier 12y ago
    Maybe you don't have to pass - just like beads on an abacus string they could oscillate up and down with some overlap. Sometimes your cage might have to pause to let another leave the zone but mostly it could work.
gus_massa 12y ago
Some of the thecnical problems are discussed in "Billion-Story Building" https://what-if.xkcd.com/94/ https://what-if.xkcd.com/94/ Another problem is the cost. Who is going to pay it? Do you want to pay it???
mikeevans 12y ago
Relevant: http://what-if.xkcd.com/94/ http://what-if.xkcd.com/94/
brudgers 12y ago
Ok, let's give your skyscraper a nice 80' x 200' floor plate. A 100 stories up, and you've probably spent a billion dollars on construction and land and entitlement...at least in the US. Less some other parts of the world, more in others. You're only half way to matching the tallest building, have just put an additional million and a half feet of expensive space into the local real-estate market, and your costs are only going up. But that doesn't really paint the right picture about how expensive it is to build upward beyond a half dozen stories or so rather than building outward or just cramming more into less space. No to put the cost of building upward in perspective: the great pyramid was the tallest building for nearly 4000 years. Lincoln Cathedral was then the tallest ever built for more than 500 [250 years if you want to say it lost the title when the spire collapsed, which brings up the point that the great pyramid would have been, but for erosion the tallest structure from 1647 to 1874, but was still the second tallest in the age of steam and iron]. So yeah, it's expensive and hard and unless you're the Pharaoh doesn't serve much purpose.
joeclark77 12y ago
They say that the tall skyscrapers sway a lot with the wind. It's perfectly safe, but it freaks people out. I've never been to the top of one to see for myself.
gdewilde 12y ago
I suggest a giant snow man

6 points by a3voices 12y ago

I don't get why nobody built a simple tower with a narrow base to best that. Is it really that hard to do, or that expensive? Why aren't there any 10,000 foot towers?

dekhn 12y ago

ask yourself, why do you need a taller building, and if so, are you sure you want to spend the money to engineer it?

VLM 12y ago

Assuming you want a serious answer, a very HN one is to discuss scalability, and unlike rope or cables or fiber, towers most certainly do NOT scale merely linearly with length. Its way, way worse. Or if you prefer to think of it this way, we don't have enough income inequality and/or world wide wealth for one plot of land to "deserve" a 10 kilofoot tower. Another fun term to google for is Euler and column buckling. That's why we don't have 75000 foot tall radio towers, which at least superficially would seem to be a great idea that could get past the scaling costs because potential revenue would scale even better with surface area within line of sight. Or even more interesting a 75 kilofoot rocket launching tower so you could use higher Isp vacuum rated nozzles at launch (if you tried that at ground level they'd buckle from the outside in)

zachlipton 12y ago

Elevators. I mean obviously there are significant structural concerns as well, but elevators are a big part of what makes building super-tall buildings uneconomic and impractical. The Elevator Conundrum, as Wikipedia dubs it (https://en.wikipedia.org/wiki/Skyscraper_design_and_construction#The_elevator_conundrum https://en.wikipedia.org/wiki/Skyscraper_design_and_construc...), means that as you build a taller building, you need more elevators to service the floors. More elevators take up more space, meaning less rentable space for occupants. While skylobbies, double-deck elevators, and other tricks can help, they don't eliminate the problem, especially since no one is willing to transfer elevators four times to get up/down. We also run into the issue of how to build a 10,000 foot elevator, which is so far outside the competence of manufacturers that it would represent a huge risk to the completion of the entire building project. I am, of course, assuming you plan to build a useful tall building instead of an empty 10,000 foot tall shell for no particular reason.

Pyrodogg 12y ago
The elevator problem is partially solved by never leaving your section of the mega tower! Work on level 120 Sleep on 73 Recreation on 145 Skyway connections to neighboring mega towers every 50-75 levels. Actually travelling to the surface world would be akin to driving for hours across the state. It's a trip and would be planned for accordingly, and happen rarely.
- 27182818284 12y ago
  >Actually travelling to the surface world would be akin to driving for hours across the state. It's a trip and would be planned for accordingly, and happen rarely. I must be missing something. 10,000ft is 1.8ish miles. That's like an 8 minute bike ride not a cross-state drive. Even if it took 30 minutes by elevator, that's a reasonable commute in cities like Chicago.
  - Pyrodogg 12y ago
    Yea, I went funny with the scale. Jumped straight from skycraper to something the size of a GSV from the Culture series.
jvvlimme 12y ago
The main problem with elevators today is that you can only have on cage per shaft. You could solve this if you could have multiple cages per shaft. A bit like how trains operate with switches and passing points. I imagine that would take some serious technical development but doesn't seem entirely out of this world. It would be easier if you have cableless lifts like the maglev lift Toshiba developed (http://www.toshiba-elevator.co.jp/elv/infoeng/technology/tec05.jsp http://www.toshiba-elevator.co.jp/elv/infoeng/technology/tec...).
- JoeAltmaier 12y ago
  Maybe you don't have to pass - just like beads on an abacus string they could oscillate up and down with some overlap. Sometimes your cage might have to pause to let another leave the zone but mostly it could work.

gus_massa 12y ago

Some of the thecnical problems are discussed in "Billion-Story Building" https://what-if.xkcd.com/94/ https://what-if.xkcd.com/94/ Another problem is the cost. Who is going to pay it? Do you want to pay it???

mikeevans 12y ago

Relevant: http://what-if.xkcd.com/94/ http://what-if.xkcd.com/94/

brudgers 12y ago

Ok, let's give your skyscraper a nice 80' x 200' floor plate. A 100 stories up, and you've probably spent a billion dollars on construction and land and entitlement...at least in the US. Less some other parts of the world, more in others. You're only half way to matching the tallest building, have just put an additional million and a half feet of expensive space into the local real-estate market, and your costs are only going up. But that doesn't really paint the right picture about how expensive it is to build upward beyond a half dozen stories or so rather than building outward or just cramming more into less space. No to put the cost of building upward in perspective: the great pyramid was the tallest building for nearly 4000 years. Lincoln Cathedral was then the tallest ever built for more than 500 [250 years if you want to say it lost the title when the spire collapsed, which brings up the point that the great pyramid would have been, but for erosion the tallest structure from 1647 to 1874, but was still the second tallest in the age of steam and iron]. So yeah, it's expensive and hard and unless you're the Pharaoh doesn't serve much purpose.

joeclark77 12y ago

They say that the tall skyscrapers sway a lot with the wind. It's perfectly safe, but it freaks people out. I've never been to the top of one to see for myself.

gdewilde 12y ago

I suggest a giant snow man