Possible to build a space tower?

[skyshrimp]

Is it possible to build a skyscraper that's so tall that it enters the ozone layer? I was imagining such a tower where customers could go to the top in elevators and view the Milky Way in bed with a glass roof in their luxury apartments :)

Obviously not just a tower without supports. Maybe with ginormous stabilizers, like a pyramid shape.Architects! Why you no build this tower yet?

 

[skyshrimp]

Ouch! This was made in Off Topic for non-critical, fun discussion

(a sky tower would be awesome though)

 

[berkeman]

Ouch! This was made in Off Topic for non-critical, fun discussion

LOL. I couldn't parse this, so I checked the thread history and see that your thread was moved from the General Discussion forum to the Engineering forum. I assume that's what you mean with your complaint?

You are asking a technical feasibility question. That deserves technical answers. I suppose we could move this thread to the SciFi forum, but even there we only allow fiction based on reasonable science...

So having said that, what do you think the technical challenges are for building such a tall structure?

 

[jrmichler]

The technical challenge is a result of the fact that each floor must support its own weight, plus the weight of every floor above it. If you build a rectangular building, then the amount of necessary structure increases every floor as you travel downward from the top floor. At some point, the bottom floor is 100% structure with zero usable space for people and elevators.

The way around that is to make the structure tapered, similar to that of the Eiffel Tower. A design study of a 4,000 meter tall building is here: https://en.wikipedia.org/wiki/X-Seed_4000. The base is 6,000 meters wide.

A good general discussion of really tall buildings: https://www.citylab.com/design/2012/08/there-limit-how-tall-buildings-can-get/2963/. Good search terms to learn more: limitations to tall buildings.

 

[DaveC426913]

Elevators and elevator banks become a big problem in tall buildings. There are solutions, but all require compromise of some form or another.

 

[Vanadium 50]

Let them take the stairs!

 

[member 656954]

It's a touch off topic but if you want to "view the Milky Way in bed with a glass roof in their luxury apartments" then this (to me) counter intuitive space elevator attached to the Moon probably trumps a building that reaches the ozone layer! And according to the researchers, it's even doable with current building materials.

https://arxiv.org/pdf/1908.09339.pdf

 

[russ_watters]

...space elevator attached to the Moon

? The moon is not going to be pleased we are trying to pull it out of orbit!

 

[member 656954]

? The moon is not going to be pleased we are trying to pull it out of orbit!

I think the Man in the Moon will understand

But it's seriously astounding to me that while a traditional space elevator has been shown to be essentially impossible to build without sci-fi story materials, we could build an elevator anchored to the Moon right now. Perhaps we need a PF crowd funded campaign to get this done!

 

[russ_watters]

I think the Man in the Moon will understand

But it's seriously astounding to me that while a traditional space elevator has been shown to be essentially impossible to build without sci-fi story materials, we could build an elevator anchored to the Moon right now. Perhaps we need a PF crowd funded campaign to get this done!

Let me be more direct: It sounds like you are saying that's an elevator connecting the Earth and Moon -- if so, no, that isn't what the paper says. It suggests building from the moon toward Earth, stopping around the altitude of geostationary orbit.

 

[DaveC426913]

Let me be more direct: It sounds like you are saying that's an elevator connecting the Earth and Moon.

I don't see him suggesting that.

He seems to be drawing attention to the fact that - due to material weight factors - a Moon-based beanstalk is far more doable than an Earth-based beanstalk.

 

[DaveC426913]

Sonuvagun. The constraints of a Moon-based beanstalk are so gentle that you don't even need to taper the cable - you could use a constant cross-section cable the whole length.

https://en.wikipedia.org/wiki/Lunar_space_elevator#Cross-Section_Profile

 

[russ_watters]

I don't see him suggesting that.

He seems to be drawing attention to the fact that - due to material weight factors - a Moon-based beanstalk is far more doable than an Earth-based beanstalk.

Perhaps...but if so, how will that help someone view the milky-way from their Earth-based apartment?

Designing a return trip from the moon doesn't help get from the Earth to the edge of space. It's unconnected to what the OP was asking.

 

[skyshrimp]

I see a pyramid structure of support beams connected from each floor to the ground. The next set of beams will get bigger exponentially as you go up a floor. The top floor would have pyramid beams 200 miles
+ long to the ground. All beams on each floor fused together. I'm guessing it would have to built in the ocean. Probably Dubai.

I recall reading that Ian Armstrong saw space as a blanket of white on the dark side of the moon due to viewing stars without light pollution.

Imagine being able to choose how much weightlessness you want to experience by booking a certain floor?*

(*random thought was for off topic random thoughts FYI)

So yeah. Each pyramid support on each floor getting bigger like a reverse Matryoshka doll. Built from the ground up and connected like honeycomb.

You'd need 20 elevators, but like Vanaduim 50 stated, there's always the stairs if the power goes out. A 60+ mile staircase decent would be great cardio (j/k) :)

 

[DaveC426913]

The top floor would have pyramid beams 200 miles
...
Imagine being able to choose how much weightlessness you want to experience by booking a certain floor?

Not nearly as exciting as it sounds.
On the top floor of a 200 mile tall building, a 150-pound tourist would weigh ... 135 pounds.

You'd need 20 elevators,

Not as simple as that. Elevators have a maximum height, above which they can't hold their own weight plus the weight of their cables. This is a problem that current skyscraper engineers contend with, and solve using one of several compromises (such as having to get out half way up and enter a different elevator).

 

[russ_watters]

I recall reading that Ian Armstrong saw space as a blanket of white on the dark side of the moon due to viewing stars without light pollution.

No, space is dark. Making the sky darker makes what you see darker, not brighter.

Imagine being able to choose how much weightlessness you want to experience by booking a certain floor?*

That would only be true for a space elevator hotel (22,000 miles+), not an edge of space hotel (50 miles).

 

[skyshrimp]

The ISS is 254 miles high and they experience weightlessness. Why 22K miles to only be true?

 

[BWV]

An elevator to the moon is feasible, but from Earth's orbit, not the surface

https://arxiv.org/pdf/1908.09339.pdf
Perhaps the biggest hurdle to mankind’s expansion throughout the Solar System is the prohibitive cost of escaping Earth’s gravitational pull. In its many forms the space elevator provides a way to circumvent this cost, allowing payloads to traverse along a cable extending from Earth to orbit. However, modern materials are not strong enough to build a cable capable of supporting its own weight. In this work we present an alternative to the classic space elevator, within reach of modern technology: The Spaceline. By extending a line, anchored on the moon, to deep within Earth’s gravity well, we can construct a stable, traversable cable allowing free movement from the vicinity of Earth to the Moon’s surface. With current materials, it is feasible to build a cable extending to close to the height of geostationary orbit, allowing easy traversal and construction between the Earth and the Moon.

 

[russ_watters]

The ISS is 254 miles high and they experience weightlessness. Why 22K miles to only be true?

The ISS is moving at almost 18,000 mph. That's what makes it be in orbit. A space elevator at 254mi is moving at 1100mph, only 50mph faster than at the surface and would feel about 85% of their surface weight (mostly due to being further away from Earth, not from the speed). Just being in space doesn't automatically make you [feel] weightless.

 

[Ibix]

Ian Armstrong

Ian Armstrong? If that wasn't just a typo I'd tend to doubt your source's accuracy...

 

[Nik_2213]

Hmm. IIRC, there are already designs for winch-free lifts, more akin to trams, that have multiple independent cabs in same shaft...

IIRC, OP's thoughts have been explored by designers of 'city towers'.
Even with active mass-dampers, single 'tapered towers' proved vulnerable to wind sway and, IIRC, tidal forces. The 'jack-up' foundations to counter settlement, uneven or otherwise, are non-trivial. There's safety / evac issues, too...
IIRC, a truly heroic Japanese mega-design met some of these concerns with a toroidal, 'ring donut' arrangement. A ring of w-i-d-e close-coupled hi-rise towers were deep-linked at enough levels for ample housing, prompt horizontal evac and, yes, 'people mover' mini-trams. The tapered towers' flexible couplings provided quake & storm resilience. The 'atrium' held a stack of circular parks / urban farms set at those link-levels. There was enough air-gap at each such level for helos, air-taxis, smoke clearance and partial natural lighting. Sprinklers & fire-monitors on underside of each atrium level formed a useful precaution...
Robust enough for Godzilla to use as cat-gym, the project would require more concrete and rebar than the 'Three Gorges Dam', so no takers yet...

 

[some bloke]

So now I'm curious - with regards to this hanging moon-ladder:

If I simplify it's construction for the sake of discussion to make it a long cable (of whatever width is needed) hanging from the moon towards the earth, with an anchor weight hanging towards the Earth which keeps it taught (but isn't close enough to the atmosphere to get dragged by it) by being pulled towards the earth;

Could you feasibly "climb" the cable from geostationary orbit height, until you get close enough for the moon to exert a meaningful pull on you and then - get this - float down holding the cable, with the weight being pulled by the Earth acting like a balloon to slow your descent? Upon landing, you release the cable and the weight falls towards the Earth (away from the moon), making the cable taught again.

would that work? I'm assuming it would take a perfectly balanced system! perhaps with a smart winch at the moon-end to recalibrate the distance from the Earth the anchor is held? Presumably you could stop at a specific location on the cable, and then be winched in until your weight (on the moon) overpowers the anchors weight (on the earth) and you slowly & safely descend?

 

[Janus]

The ISS is 254 miles high and they experience weightlessness. Why 22K miles to only be true?

To add to what Russ said. Objects in orbit are in free-fall. They are essentially falling around the Earth. This includes the occupants as well. Astronauts are weightless in the ISS because they're response to gravity and the station response to gravity are essentially the same. With a tall tower, the floor you are standing on is supported by the structure and is not free to fall. You in turn are stopped from falling by that floor. The upward force provided by the floor preventing your fall is what you feel as "weight". And while gravity does get weaker with height, it doesn't do so that fast. In order for it to fall to even 1/2 strength, you would need to be ~ 4/10 of an Earth radius above the surface of the Earth (~1650 miles)

 

[DaveC426913]

There's a few misconceptions here.

So now I'm curious - with regards to this hanging moon-ladder:

If I simplify it's construction for the sake of discussion to make it a long cable (of whatever width is needed) hanging from the moon towards the earth, with an anchor weight hanging towards the Earth which keeps it taught (but isn't close enough to the atmosphere to get dragged by it) by being pulled towards the earth;

It doesn't need to be "weighted towards Earth". Space elevators are stabilized by the rotation of their parent body - in this case the Moon.

Could you feasibly "climb" the cable from geostationary orbit height, until you get close enough for the moon to exert a meaningful pull on you and then - get this - float down holding the cable, with the weight being pulled by the Earth acting like a balloon to slow your descent?

Yes, you would climb to a point on the cable to the point where their pull balances out, with your weight getting less and less until you weigh zero. Then you reverse your orientation head-over-heels and start climbing down to the Moon, - weight slowly increasing as you go.

Upon landing, you release the cable and the weight falls towards the Earth (away from the moon), making the cable taught again.
would that work? I'm assuming it would take a perfectly balanced system! perhaps with a smart winch at the moon-end to recalibrate the distance from the Earth the anchor is held? Presumably you could stop at a specific location on the cable, and then be winched in until your weight (on the moon) overpowers the anchors weight (on the earth) and you slowly & safely descend?

You don't need this. The cable is attached to the Moon.

 

[russ_watters]

Could you feasibly "climb" the cable from geostationary orbit height...

Yes, but please note that an object in geostationary orbit is already traveling much faster than the end of the ladder, so it would be a waste of energy to try to slow down to get on to the ladder.

 

[Janus]

Yes, but please note that an object in geostationary orbit is already traveling much faster than the end of the ladder, so it would be a waste of energy to try to slow down to get on to the ladder.

To be fair, he said geostationary orbit height. It is possible to reach that altitude without actually attaining orbit at that height. If you are accurate with your launch speed, timing, and angle, it would be possible to arrive at the cable end with low relative relative velocity. It would be a sub-orbital trajectory of high eccentricity.

That being said, one thing that also would need to account for is that fact that the orbital plane of the Moon and the equatorial plane of the Earth are not aligned. The end of the cable would "drift" North and South of the Equator. This would complicate the launch parameters

 

[russ_watters]

To be fair, he said geostationary orbit height. It is possible to reach that altitude without actually attaining orbit at that height. If you are accurate with your launch speed, timing, and angle, it would be possible to arrive at the cable end with low relative relative velocity. It would be a sub-orbital trajectory of high eccentricity.

Yep, but that's a tall order from a risk perpective; failure to dock = unplanned re-entry.

 

[Janus]

Yep, but that's a tall order from a risk perpective; failure to dock = unplanned re-entry

Never said it would easy

 

[some bloke]

You don't need this. The cable is attached to the Moon.

What I was thinking (just to clarify) is that the weight of the anchor could be calibrated such that when you get past a "tipping point", the force exerted on you (or the vessel in which you are travelling, which is itself moving along the cable towards the moon) would overcome the force exerted on the anchor by the earth, and so the entire structure would fall towards the moon, slowly, allowing for a gentle landing.

I appreciate that this would be unnecessary as the vessel could simply continue to move down (up?) the cable until it got to the moon, but I just like to think of a Mary Poppins style descent to the moon!