# 100 mile high mega-tall building physically possible?

The superman protagonist in my story built that building (over night--at least the shell)-

Base on lower Manhattan--the building is 0.6 mi (1 km) square up to ~5 mi up where it cantilevers out to 3 times the floor area up to about 65 mi where its double the base; and finally roughly 0.3 sqr miles in the red area to the top. First km of height is glass enclosed, as per drawing (small panes).

Roughly 25 000 floors! First 35-40 miles are residential, a vertical city divided into 10 story sections. Next 30-40 mi commercial-low grav factories, space launch facilities, etc. Top few miles are dedicated to super guy and his shenanigans. :)

Using existing building materials, is this possible?

Edit: Superguy changed his plans. He's building two additional skyscrapers, each 95 miles tall. One's in Raritan Bay, the other in New Jersey. Connecting all three are various sky-bridges, I think they call them.

Here's the base view with the Jersey tower in the background.

• Short answer: no – John Dvorak Dec 1 '16 at 17:25
• Slightly longer answer: Your building would be four times taller than a space elevator, and the floors quarter way through would have to deal with microgravity - and the top floor would experience 3G just being flung around by Earth – John Dvorak Dec 1 '16 at 17:28
• "is this possible?" implies Reality Check so I added the tag to make things clear. – AndyD273 Dec 1 '16 at 18:21
• For the 8,000th time. BUILDINGS AND HOW TO BUILD THEM ARE PERFECTLY ON TOPIC. – James Dec 1 '16 at 19:11
• @JanDvorak how is 100 miles 4× taller than a space elevator? – JDługosz Dec 1 '16 at 20:20

No.

You have some serious engineering issues.

If you have 25,000 floors, then even with no 'mushroom' (expanding floors) you have 25,000 square km of floor space. That's 25 billion square meters. If you had 100 square meter apartments, and similar space for support facilities you have 125 million apartments. At 2 people each average, you have 2/3 of the population of the U.S. living in your tower. I've ignored the business aspects, much I ignored the expansion.

Even at present with 100 story office towers, a major problem is getting people in and out. At present, one of the tricks is that it takes 2 elevator trips to get anywhere. Some elevators stop at multiples of 10-20 floors. E.g. They stop a 10, 20, 30, but don't stop at the floors between. These elevators can accelerate and run at much faster speeds. The secondary elevators run slower, but only have a short range of floors. This allows you to put several slow elevators in the same shaft.

How long does it take to evacuate? Ignoring the elevator problem. Assume that the entire perimeter is doors. Say a pair of doors every 4 meters. There are 1000 pairs of doors. Everyone walks at 4 mph, or about 2 m/s, 1 meter apart. Each door then exits 2 people per second. 1000 pairs is 2000 doors, so 4000 people per second.

125,000,000/4000 = 32,000 seconds. 9 hours.

How far do they have to go? 125 million people at 1 sq. m each is 125 square km. About 11 km away.

We have a problem before that however. Suppose we have 1 high speed elevator every 50 meters, over the entire base. 400 elevators total. On the average the elevator come down 80 km. If they ran at the speed of a high speed train, say 320 km/hour, it takes 30 minutes per round trip. If the elevator has the usual capacity of about 15, then 400 shafts delivering a person every 2 minutes is 200 passengers per hour.

Clearly we don't have enough elevators. Lets's make half the base elevators. One every 10 meters. So we have 100 x 100 grid of elevators or 10,000 elevators. Still stuck at 5000 people per hour. Takes 25,000 hours to get everyone down. Somewhat under 3 years.

How would you support this structure? There is a reason that the earth can stack mountains only about 7 miles above sea level.

I did tour of the Bunker Hill Sullivan mine. At 5000 feet below the surface, they have to rebore the tunnels periodically: There's enough creep of the rock, that it gets out of true. They also bolt chain link fence to the walls and ceiling. Rock spalls off the ceiling. Now buildings are not as dense as rock, but we're not talking any measly 7 miles either.

You have some serious wind load issues where it passes through the tropopause.

How do you keep if from zigging out of line. You have a building with a 160 to 1 height/width ratio. So 1 cm square base by 160 cm height. Load goes up with the cube of the linear size ratio, but strength goes up with only the square.

Try this: Make a stick of those dimensions -- 1 cm x 1 cm x 160 cm (5 feet)

Duct tape a pop bottle to the top end. Partially fill it with water. Now holding it the bottom end, with the end stationary on the floor, keep it balanced. This is best done outside on a windy day. The bottle of water is the rest of the load on the building.

(This is fairly easy to do if you can move the base, as you are rotating the stick around it's center of mass. You have a much longer lever arm, and the load has half the lever arm as with a stationary base.)

Keep in mind in this model, that your hand is 10 cm tall -- You aren't going to hold the bottom 10 km of your tower.

• Maybe they don’t have elevators but book a flight from one level to another. – JDługosz Dec 4 '16 at 1:18
• @Sherwood Botsford -Your excellent answer makes a lot of sense. I figure the residential section has ~9500 floors, but your conclusions about evacuation, transit, etc, undoubtedly hold anyways. Still (calcs of my own)... 250 million times .4 equals 100 million... but as I mentioned, each ten stories makes up a city/suburb; has its own elevators, escalators... shopping malls, parks, grocery stores, bodegas, bars, professional spaces, etc. The commercial section has its own set of elevators attached exterior to the outside walls. In both cases, the main elevators--ground floor to topmost--stop.. – catsteevens Dec 4 '16 at 1:50
• (cont) at maybe a couple thousand floors, which I guess makes building evac even worse. Oh well... a lot to think about for a single chapter in my book. And the protag ends up tearing the building down after all. :) – catsteevens Dec 4 '16 at 1:55
• Just a crazy thought--what if each elevator was a big car with several smaller elevators in each...IOW, elevators within elevators. The main car serves, off the top of my head, ten floors at a stop. You climb aboard on ground level, while the car rises you step into the smaller elevator to get off at your choice of 10 floors at a stop. (head explodes) – catsteevens Dec 4 '16 at 2:21
• To expand, since the main elevators stop once every ten floors in the residential section, how about this: you step aboard at ground level, go to an interior elevator with a choice of three floors... near the end of the 5 mile rise to the residential section, an alert sounds and the main car separates (hydraulically, however) into 3 sections, i.e., vertically its 30 stories tall. Thereby servicing 30 floors at each stop. Or, do away with the interior elevators and have a 3 floor entrance on the ground floor. – catsteevens Dec 4 '16 at 3:06

Actual answer is a guarded "Yes", with lots of caveats.

Firstly, it is theoretically possible to build compression towers to heights of at least 20km using structural materials like steel or high strength aluminum. It is even more possible if you want to eat the extra costs of using exotic materials like Titanium or carbon fibre reinforced composites, which are much lighter but have similar strength to steel. This sort of tower would be essentially an open truss work, and like the Eiffel Tower, it would need to have a very wide base to ensure stability from the various forces acting on it, and to ensure the tower has a stable base to support the weight.

http://www.citylab.com/design/2012/08/there-limit-how-tall-buildings-can-get/2963/

http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.1541305

Even more exotic construction might be used, with dynamic elements supplying strength and support. A Canadian company wants to build a 20km tall tower using inflatable sections, for example. Other sorts of dynamic structures are also possible, with the ultimate expression being the "Space Fountain". The primary issue with the Space Fountain, and indeed any dynamically stable structure is that it depends on the uninterrupted flow of the dynamic elements. A power interruption, a kink in the magnetic track or any other small fault could lead to the catastrophic destruction of the tower, particularly since the energy of the moving parts is so high.

Diagram of Space Fountain

Of course for something like this to be built, there would need to be a compelling reason. In the case of Geoffrey A. Landis' "Tall Tower", the device is meant to be a launch platform for rockets, with the advantage of eliminating a great deal of atmospheric drag by simply lifting the rocket to the top to the tower for launch. (Obviously economic considerations don't apply to super beings). In fact, although it seems quite possible to build even a relatively ordinary skyscraper to nights of a mile (1.6km), and indeed architect Frank Lloyd Wright had drawn up a design as far back as the early 1950's, there is no economic justification for such a structure, and the added expenses of stability measures, special elevators and so on simply make such a thing impractically expensive, or you would have to charge absurd rents to pay the cost of the structure.

WRT a 100 mile high tower, there are two approaches. The tower could be built directly as a gigantic construct, or you could build such a thing if you used the Landis "Tall Tower" as the base and supporting structure for a space fountain. This would protect the high velocity pellet streams of the space elevator from disruption and keep the magnetic tracks stable in the very critical base part of the structure, and the fountain would carry on out of the atmosphere.

**Short answer: No; not with our local gravity, natural laws and best materials to date.

Optimistic answer: Maybe, if we could achieve the full theoretical strength of carbon nanotubes and make them as long as we'd like.

Unless you add an extension up to/past geosynchronous orbit.** Even making this the base of a Skyhook (and assuming we could make perfect carbon nanotubes of arbitrary length), it's not exactly trivial. A big hydrogen or helium blimp wouldn't help; you're already well above virtually all of the atmosphere.

The strength of materials ultimately comes down to the strength of inter-atom bonds. The carbon-carbon bond in CNT's (See: https://en.wikipedia.org/wiki/Carbon_nanotube.) is the best we know of. Adamantium (and Niven's Scrith) are sadly unavailable.)

• Jan Dvorak's comment above involved, AIUI, a centrifugal (?) force on the upper floors. Would this help counter-act gravity and therefore stress on the building members? – catsteevens Dec 1 '16 at 18:16
• Even with carbon nanotubes, a frame structure like that is going to experience a very high bending moment (think of how it's much easier to break a long stick than a short one), and will buckle. That's why space elevators and the like are based on cables in tension. And it would have to be located at the equator, not in Manhattan. – jamesqf Dec 1 '16 at 18:29
• No it wouldn't, because it would have to survive force of being dragged. It does, however, allow use of nanotubes that are strongest when they are pulled, and soft to bend. – Mołot Dec 1 '16 at 18:31
• @catsteevens: Insignificant help from centripetal acceleration at 100 miles up; the break-even height (where the top floor would be at zero g) is 22,236 mi) above mean sea level. I'll do a better min-trength estimate tonight; I may have been too harsh. – Catalyst Dec 1 '16 at 18:41
• @catsteevens: Gravity, basically. Think of trying to balance a broomstick: it's an unstable equilibrium, so any slight movement off the perfect balance point increases the force moving it away from equilibrium, which increase the force even further. Since the bottom here is fixed, any slight force on upper stories - winds, or even someone walking around on the top floor - forces it out of equilibrium, and with say ~50 miles of lever arm, the tower bends and then snaps in the middle. – jamesqf Dec 2 '16 at 18:36

The answer is no with current tech, yes with crazy-soft-science-future tech. XKCD did it:

In this article Randall Munroe XKCD guy postulates to a little girl on this by skipping over some basic laws of nature/logistics/economics and ignoring hazards like the structure "falling over and smashing into the planet like the giant meteor that killed the dinosaurs".

"Maybe, someday, you could build a giant tower to space. I'm pretty sure it won't be made of peanut butter, though."

• Hi Nahshon, could you please provide a summary of what's on the link - link-answer-only answers are generally frowned upon in case the link changes or dies over time (hopefully XKCD will be around forever though!) – Mikey Apr 24 '17 at 19:52
• XKCD forever. Amen. holding hands together, bowing head, humming nonsensically, in veneration – Nahshon paz Apr 26 '17 at 12:18