Japanese Space-Elevator Experiment next week

[Cassel]

This is something wonderful, I hope the experiment will succeed. Even if they did not manage to achieve materials of such strength that pulling the capsule from Earth into orbit would be possible, I hope they could at least build an elevator on the Moon or Mars.

https://www.space.com/41278-japan-space-elevator-cubesats-experiment.html

[Green Baron]

Interesting, but i don't understand the objective.

That the car actually moves along the cable ? And the cable wont coil up or knot ?

Edited September 10, 2018 by Green Baron

[kerbiloid]

What a shame that we don't have a rail/cable-way in KSP.

[magnemoe]

33 minutes ago, kerbiloid said:

What a shame that we don't have a rail/cable-way in KSP.

We have the KAS winches, I used it to land Jeb on Jool back in 0.18 or 0.19 then it had an surface. Needed to connect multiple winches after each other. 
Was unable to plant a flag so I posted an bug report, next version the surface was gone. 

[kerbiloid]

5 minutes ago, magnemoe said:

We have the KAS winches, I used it to land Jeb on Jool back in 0.18 or 0.19 then it had an surface. Needed to connect multiple winches after each other. 

We can move the end of the cable, but can we run a carriage along it? Afaik, no.

5 minutes ago, magnemoe said:

I posted an bug report, next version the surface was gone. 

So, if somebody had a planetary base on it, it's gone, too. 

Edited September 10, 2018 by kerbiloid

[YNM]

The elevator isn't a winch, right ? It actually rolls on the surface ?

If anything, this would be a good demo on whether we can use wheels with traction in microgravity, not so much about space elevators.

[Bill Phil]

This definitely looks more like a test of transportation between two spacecraft connected by cable than anything to do with a space elevator.

[kerbiloid]

And like this.
 

Spoiler

 

[KerikBalm]

I don't see the point of doing a space elevator when we could do an orbital ring instead.

A space elevator needs to extend well past geostationary orbit. GSO is 35,786 km

The circumference of the earth is 40,075 km

Thus the total length of cable you need for both an orbital ring and a space elevator is very similar... but an orbital ring can be built with material with the tensile strength of steel, a space elevator cannot.

An orbital ring can serve many more locations, gets you to space faster, and doesn't have to be on the equator.

https://en.wikipedia.org/wiki/Orbital_ring

So why bother with a "classic" space elevator?

[Scotius]

I wonder how they intend to keep the cable taut. Centrifugal force, most probably.

[KerikBalm]

yea, centrifugal force is most likely, just like a full scale elevator.

Still, why bother? We could do an orbital ring much easier.

I particularly like the idea of putting the ring on the surface of the earth, and then spinning it into space...

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The GPV ring is located on a specially equipped overpass, encircling the Earth. In the initial condition it is fixed on the overpass.

With the help of an external energy source one of the rotors spins up to speed higher than the First Cosmic Velocity at sea level (i.e. orbital speed at sea level, same as the escape velocity divided by root two). Due to the centrifugal force, the rotor (having reached the First Cosmic Velocity) balances itself and then seeks to "fly" up, producing lift force. The rotor's speed is to be a little more than necessary to balance the ring.

Humans have built more than enough roads to encircle the earth, and we don't need to start with the ring on the equator...

It would be so awesome to see an expandable ring just start to levitate and fly into the sky, trailing cables underneath that would be the basis for the various stations to reach it.

[Cassel]

6 hours ago, KerikBalm said:

I don't see the point of doing a space elevator when we could do an orbital ring instead.

A space elevator needs to extend well past geostationary orbit. GSO is 35,786 km

The circumference of the earth is 40,075 km

Thus the total length of cable you need for both an orbital ring and a space elevator is very similar... but an orbital ring can be built with material with the tensile strength of steel, a space elevator cannot.

An orbital ring can serve many more locations, gets you to space faster, and doesn't have to be on the equator.

https://en.wikipedia.org/wiki/Orbital_ring

So why bother with a "classic" space elevator?

But you need this ring at 400+km? What makes it larger and you still need cable to reach Earth.

What would happen if part of cable would snap and fall on city?

[KerikBalm]

Yes, the ring would need to expand a bit, but going +300 km from 6,300 km means it only needs to expand by about 5%... which could conceivably be done by elasticity alone.

The cable that reaches Earth could just be steel, because its only 300 km of cable, not 40,000 km of cable.

[Cassel]

3 hours ago, KerikBalm said:

Yes, the ring would need to expand a bit, but going +300 km from 6,300 km means it only needs to expand by about 5%... which could conceivably be done by elasticity alone.

The cable that reaches Earth could just be steel, because its only 300 km of cable, not 40,000 km of cable.

Steel cable moving... how fast exactly in atmosphere? :-)

I see few problems, like I said what if cable breaks and falls on city? There is no way to prevent that.
If it is only on 300km it will lose speed over time like ISS?

[KerikBalm]

moving how fast in the atmosphere? zero

Don't put the cable over a city.

The vertical cables go to a station, which is essentially a maglev train riding on the ring cable, which is spinning at over orbital velocity.

The ring can be sped up and precessed by virtue of the maglev trains and the connection to the ground... so the only reason for it to lose speed over time is if all stations stop maintaining its speed.

All together, there's a lot less stress on the cables, it takes less materials, the materials we have now are sufficient, its much less complicated to construct, and much more versatile.

Space elevators in the sense of single cables up past GSO to space are not very attractive in comparison.

*edit: may i also point out that if a space elevator cable breaks (lets say it breaks in the middle of a 40,000 km cable with a counterweight on the end), then you have 20,000 km of cable falling to Earth, and your counterweight gets flung off into a high and eliptic orbit, the system is destroyed.

Meanwhile an orbital ring can have multiple stations with their own cables (like spokes), and can be fine as long as there are 2 spokes on roughly opposite sides.

Edited September 12, 2018 by KerikBalm

[KG3]

6 minutes ago, KerikBalm said:

 

The vertical cables go to a station, which is essentially a maglev train riding on the ring cable, which is spinning at over orbital velocity.

The ring can be sped up and precessed by virtue of the maglev trains and the connection to the ground... so the only reason for it to lose speed over time is if all stations stop maintaining its speed.

You can send a payload up to 300 km via a cable but you still need to get it up to orbital velocity.  The space elevator does this just by taking the payload up to GSO. 

[KerikBalm]

Yea, it gets up to 300 km (or 400, or 500, or 600, whatever), and then uses the ring to accelerate to orbital velocity.

The trip to orbit would be much faster, travelling 35,000km to GSO along a cable, at a limited speed because going too fast will make the cable sway/wobble too much, would take a long time...

An orbital ring on the other hand can have stations all over the world bringing stuff up to the ring, just a short 300 km trip up. The cargo capacity per day would be much much higher

[Bill Phil]

12 hours ago, KerikBalm said:

I don't see the point of doing a space elevator when we could do an orbital ring instead.

A space elevator needs to extend well past geostationary orbit. GSO is 35,786 km

The circumference of the earth is 40,075 km

Thus the total length of cable you need for both an orbital ring and a space elevator is very similar... but an orbital ring can be built with material with the tensile strength of steel, a space elevator cannot.

An orbital ring can serve many more locations, gets you to space faster, and doesn't have to be on the equator.

https://en.wikipedia.org/wiki/Orbital_ring

So why bother with a "classic" space elevator?

Maybe a lofstrom loop? Even shorter, just 2000 km and some more for the lift cables.

[Cassel]

11 hours ago, KerikBalm said:

moving how fast in the atmosphere? zero

Don't put the cable over a city.

The vertical cables go to a station, which is essentially a maglev train riding on the ring cable, which is spinning at over orbital velocity.
 

Now I have even more questions and doubts.

The idea of a train traveling on the cable is nice, but if this train will move quickly and will be heavy, what about the centrifugal force and the forces applied on the cable? At this point, it will no longer be a cable just train tracks in orbit.
The train would have to move around 26,000 km / h? What will power it?

Edit:
I omitted one thing here. If the train moves at zero speed in relation to the Earth, does it mean that it will be falling and pulling the cable behind it?
 

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The ring can be sped up and precessed by virtue of the maglev trains and the connection to the ground... so the only reason for it to lose speed over time is if all stations stop maintaining its speed.
 

Changing the speed of the cable involves a change in its length. At 300 km, the cable will have to have a different length than at 400 km, right?

The very process of attaching an orbiting cable to the planet and spinning it faster will require many stations and unprecedented coordination in places thousands of miles away on the surface of the planet. For this you need to read the data from the sensors on orbit on the cable. Cable itself at that moment would be loaded and exposed to tearing.
 

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All together, there's a lot less stress on the cables, it takes less materials, the materials we have now are sufficient, its much less complicated to construct, and much more versatile.

 

The forces acting on the cable would be huge. You need a lot of trains running on the cable, each of them needs power. Each train has to pull the "docking cable" with the planet. On the surface of the planet, you need stations designed for attaching holders.
 

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Space elevators in the sense of single cables up past GSO to space are not very attractive in comparison.
 

They are much simpler and such elevators can operate independently. In your idea, any acceleration of the cargo pulled from the surface of the planet requires the coordination of each train moving on the cable.
 

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*edit: may i also point out that if a space elevator cable breaks (lets say it breaks in the middle of a 40,000 km cable with a counterweight on the end), then you have 20,000 km of cable falling to Earth, and your counterweight gets flung off into a high and eliptic orbit, the system is destroyed.

Meanwhile an orbital ring can have multiple stations with their own cables (like spokes), and can be fine as long as there are 2 spokes on roughly opposite sides.

If the cosmic elevator breaks down and the cable breaks, should it fall vertically down?
Additional security devices can also be mounted on such a cable, for example a system that when the break is detected will start the engines and throw the falling part of the cable into a higher orbit. Alternatively, drones may circulate between GSO and 400 km, which will catch falling pieces of cable at the moment of failure.

If the cable from your idea breaks, will it fly to Earth at 26,000 km / h? This can cut down every skyscraper on its way from the top to the basement? Well, we also have a trains that are falling and crashing on Earth.
The cable cracked in half will act like a whip of 40,000km length? One part of it will start to fall to Earth, and the other end can change orbit and cut in half any satellite within range or I am missing something?

Edited September 13, 2018 by Cassel

[kerbiloid]

Why need 300 km?
Isn't even 50 km enough good? That's what the first stages do.

[KerikBalm]

10 hours ago, Cassel said:

The idea of a train traveling on the cable is nice, but if this train will move quickly and will be heavy, what about the centrifugal force and the forces applied on the cable? At this point, it will no longer be a cable just train tracks in orbit.

If you want to think of it that way, fine. To avoid confusion, lets call the "track" in orbit a "ring" (it can be a cable), and the cables/tracks up to the "trains" we'll call "spokes"

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The train would have to move around 26,000 km / h? What will power it?

Solar power would be fine. Keep in mind, relative to the earth's surface, the train is stationary. By virtue of being a maglev train, there is almost no friction with the ring. All the train needs to do is repel the ring/cable/"traintrack" and occasionally accelerate the ring if it slows down too much. (by virtue of the connection via spokes to the Earth, it can do this)

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I omitted one thing here. If the train moves at zero speed in relation to the Earth, does it mean that it will be falling and pulling the cable behind it?

Umm, everything in orbit is "falling", I'm not 100% sure what you mean here. The "train" (lets call it a station from now on) rests on the cable, and the cables "centrifugal force" is what holds up the station.

 

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Changing the speed of the cable involves a change in its length. At 300 km, the cable will have to have a different length than at 400 km, right?

Changing the altitude of the ring involves changing the length of the ring, generally speaking. With 400km spokes the ring will need to be a small % longer than with 400 km spokes (assuming the ring has the same shape, note that the ring can be an elipse and not a true circle)

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The very process of attaching an orbiting cable to the planet and spinning it faster will require many stations and unprecedented coordination in places thousands of miles away on the surface of the planet. For this you need to read the data from the sensors on orbit on the cable. Cable itself at that moment would be loaded and exposed to tearing.

You only need 2 stations

https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/OrbitalRing.svg/316px-OrbitalRing.svg.png

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The forces acting on the cable would be huge. You need a lot of trains running on the cable, each of them needs power. Each train has to pull the "docking cable" with the planet. On the surface of the planet, you need stations designed for attaching holders.

The whole point is that the forces acting on the cables (spokes and rings) are much less than that of a space elevator. I don't even know what you're talking about with a "docking cable". On the surface you attach ones end of the spokes. At the top of the spokes there is a station magnetically suspended on the spinning ring, these stations stabilize the ring, as the ring holds them up by virture of spinning faster than orbital velocity. When a payload gets the the station at the top of the spoke, it then is accelerated along the ring and into orbit.

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They are much simpler and such elevators can operate independently. In your idea, any acceleration of the cargo pulled from the surface of the planet requires the coordination of each train moving on the cable.

"simpler" is relative. the change in velocity of the payload as it ascends (its initial velocity would be 2*pi*Earth's radius/24 hours, at release its velocity is 2*pi*(Earth's radius+35,000 km)/24 hours. This results in a lot of swaying of the cable as it has to accelerated the payload prograde in addition to raising its altitude. The speed of ascent must be limited to prevent destructive oscillation, and the payload capacity is thus very limited.

Construction of a space elevator is also more complicated. The materials required are also much more complex, and have to be entirely lofted into orbit. Each elevator would be independent... but one could also have independent rings too.

It comes down to 2 ground stations vs 1, and and actively maintained system that can actively dampen oscillations from sending up cargo, vs a passive system that requires a lot of waiting for oscillations to subside.

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If the cosmic elevator breaks down and the cable breaks, should it fall vertically down?

No... the velocity at GSO only appears stationary, its actually moving much faster than the surface of the Earth. It completes an orbit in 24 hours, but the circumference of that orbit is much greater. If you were to pull everything down from GSO and below, the elevator cable would accelerate forward relative to the ground... You'd have a 35,000 km long path of destruction under the cable, nearly enough to encircle the Earth.

Everything below GSO in a space elevator is sub orbital

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Additional security devices can also be mounted on such a cable, for example a system that when the break is detected will start the engines and throw the falling part of the cable into a higher orbit.

No... everything below GSO in a space elevator is sub orbital. When a break occurs, everything above the break is flung into an eliptical orbit by virtue of the connection to the countermass above GSO.

Everything below GSO on the otherhand is suborbital, and everything below the break comes crashing down. Engines aren't going to get the whole thing into orbit, especially as its still connected to the ground (and we're talking potentially 35,000 km or cable that you want your "security devices" to loft into orbit if you also sever the connection at the bottom)

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Alternatively, drones may circulate between GSO and 400 km, which will catch falling pieces of cable at the moment of failure.

No... the falling pieces of cable are obscenely large, and the drones would be at orbital velocity. At 400 km, the cable's velocity (relative to a non rotating reference frame centered on the Earth) would be about 450 m/s, while the drone circulating in orbit would be going about 7,600 m/s... its not going to catch anything at those speeds, unless it has the dV to get to orbit by itself (reversability of orbits), and then accelerate a cable several thousand km long to orbit.

No... just no... nothing short of a nuclear (as in orion drive, nuclear detonations, not nuclear thermal with controlled reactions) or antimatter engine is going to be able to do that. If you have ships with that kind of dV and power, why bother with these elevators and such?

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If the cable from your idea breaks, will it fly to Earth at 26,000 km / h? This can cut down every skyscraper on its way from the top to the basement? Well, we also have a trains that are falling and crashing on Earth.

If the cable breaks, given that it was rotating at above orbital velocity, it flings itself into a higher orbit. The stations fall. So you have 2 places on the earth at risk of things falling straight down (and they could be in the middle of a desert or the ocean) from essentially zero surface velocity.

And there could be redundant ring-cables holding the stations up to prevent that (keeping in mind that because this system doesn't stress materials to their absolute limits, one can have redudancy, which is not possible with a space elevator and even exotic carbon nanotube filaments)

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The cable cracked in half will act like a whip of 40,000km length? One part of it will start to fall to Earth, and the other end can change orbit and cut in half any satellite within range or I am missing something?

no, the thing would expand outward. It wold be a bit unstable though, so for safety, you'd want to break it at multiple parts along its length so the segments of cable orbit independently.

Also, keep in mind how big space is... while debris is an issue for even current sats, the cable could easily pass 10m above or below other sats. Also if we had an orbital ring, I'd hope we'd also have cleaned up the junk in low orbit, and the cable wouldn't be a threat to stuff in high enough orbits (how high depends on the initial height of the ring, and how much faster than orbital velocity it is spun, which itself depends on how much you want it to be able to lift at one time).

*edit* also keep in mind that a space elevator is a high threat to stuff in orbit below (and above GSO), because everywhere except at GSO its going much slower or faster than orbital velocity. in low orbit, everything in orbit will be whizzing by the cable at upwards of 7,000 m/s, every 90 minutes (as opposed to much much slower relative velocities much much less frequently for two objects in similar orbits).

Both concepts essentially require that we clean up low orbit. An orbital ring could be built low enough where residual atmospheric drag has already done that for us (like at 100 km if desired, although this would increase the power requirements to keep operating the ring, it would still be relatively low, and the stations could just be solar powered)

Edited September 13, 2018 by KerikBalm

[KerikBalm]

12 hours ago, Bill Phil said:

Maybe a lofstrom loop? Even shorter, just 2000 km and some more for the lift cables.

Yea, one of those would be cool too, they were after all initially called "Partial Orbital Ring System (PORS)". Somehow it seems harder to keep in operation to me, and the raising and lowering of the loop when not in operation also seems a bit sketchy to me, but maybe it is better than a full on orbital ring.

The Sahara desert seems like a good place to put one, it could be solar powered, and I'm sure the local countries could be enticed into allowing the construction (it would bring a lot of money and economic benefits)... but at 2000 km long, it would involve multiple African nations. The political consequences of control of it would be... interesting to say the least.

[Cassel]

12 minutes ago, KerikBalm said:

Solar power would be fine. Keep in mind, relative to the earth's surface, the train is stationary. By virtue of being a maglev train, there is almost no friction with the ring. All the train needs to do is repel the ring/cable/"traintrack" and occasionally accelerate the ring if it slows down too much. (by virtue of the connection via spokes to the Earth, it can do this)
 

Well, Maglev is the answer to everything. Only that the maglev train moves on tracks built of magnets, and you write about a cable that is supposed to be light.
The maglev speed record is around 600 km/h, and you need over 26,000 km/h on orbit, you are missing a bit?

 

12 minutes ago, KerikBalm said:

Umm, everything in orbit is "falling", I'm not 100% sure what you mean here. The "train" (lets call it a station from now on) rests on the cable, and the cables "centrifugal force" is what holds up the station.

So everything falling in orbit, but your train would be falling as fast as a stone ejected from a vertical space elevator.
An orbital cable (maglev tracks) would have to keep the mass of the train, the mass of the cable reaching the Earth's surface and the mass of the cargo you are pulling into orbit.
I do not think that the centrifugal force of the cable in orbit is enough to keep this weight.
 

12 minutes ago, KerikBalm said:

 

Changing the altitude of the ring involves changing the length of the ring, generally speaking. With 400km spokes the ring will need to be a small % longer than with 400 km spokes (assuming the ring has the same shape, note that the ring can be an elipse and not a true circle)
 

 

In that case, there must be elements in which there will be a folded cable (maglev tracks) and a mechanism that will unfold it?
 

12 minutes ago, KerikBalm said:

You only need 2 stations

 

So changing the speed of the cable will require that each of these two trains, drag half the weight of the entire structure?
 

12 minutes ago, KerikBalm said:

Construction of a space elevator is also more complicated. The materials required are also much more complex, and have to be entirely lofted into orbit. Each elevator would be independent... but one could also have independent rings too.
 

The construction of a normal elevator is simple, as you wrote, everything is a matter of appropriate material and it can be built. There are many complications in your idea and many things may fail.
 

12 minutes ago, KerikBalm said:

If you were to pull everything down from GSO and below, the elevator cable would accelerate forward relative to the ground... You'd have a 35,000 km long path of destruction under the cable, nearly enough to encircle the Earth.
 

Unless it was cut off on Earth? Then he should climb the orbit himself, because of the speed differences between the GSO and the surface of the planet?
 

12 minutes ago, KerikBalm said:

No... everything below GSO in a space elevator is sub orbital. When a break occurs, everything above the break is flung into an eliptical orbit by virtue of the connection to the countermass above GSO.
 

So the tensile strength of the cable can not be as large as you say. The counterweight on the GSO will pull up some of the cable's weight.
 

 

[KerikBalm]

24 minutes ago, Cassel said:

Well, Maglev is the answer to everything. Only that the maglev train moves on tracks built of magnets, and you write about a cable that is supposed to be light.
The maglev speed record is around 600 km/h, and you need over 26,000 km/h on orbit, you are missing a bit?

https://en.wikipedia.org/wiki/Maglev

"The power needed for levitation is typically not a large percentage of the overall energy consumption of a high speed maglev system. Overcoming drag, which makes all land transport more energy intensive at higher speeds, takes up the most energy. Vactrain technology has been proposed as a means to overcome this limitation."

Drag is irrelevant at the proposed altitudes, speed achieved at 1 atm is irrelevant here.

The mass of the orbital cable isn't so important here. The tensile strength for the ring doesn't need to be so high (depends how much faster than orbital velocity you want to spin it)

Also note:

https://en.wikipedia.org/wiki/Diamagnetism

The ring does not need to be magnetic for the station to repel from the ring. If the ring is made of a diamagnetic material (or contains a diamagentic material, it could be mostly kevlar with a diamagnetic track), the station can repel from it and accelerate the ring. The ring doesn't need a complex magnetic system, only the stations on the spokes

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So everything falling in orbit, but your train would be falling as fast as a stone ejected from a vertical space elevator.

No... well... that depends what height from the vertical space elevator it was ejected from. From the station of a ring, it would fall as if it had just been dropped from 300 km (assuming the ring is at 300 km). If something fell from a vertical space elevator, it could hit the ground at a velocity fairly close to escape velocity - depending how high up the vertical space elevator.

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An orbital cable (maglev tracks) would have to keep the mass of the train, the mass of the cable reaching the Earth's surface and the mass of the cargo you are pulling into orbit.
I do not think that the centrifugal force of the cable in orbit is enough to keep this weight.

What you think, without math to back it up, is fairly irrelevant. Also keep in mind, its exactly centrifugal force that keeps a "classic" space elevator upright. Keep in mind the ring would be >40,000 km in circumference, the mass of the spoke-cable (300 km) is pretty tiny in comparison, and so would be the mass of the 2 station-trains.

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In that case, there must be elements in which there will be a folded cable (maglev tracks) and a mechanism that will unfold it?

That case was for changing the altitude of the ring... and there doesn't need to be a foldered cable. It could simply be elastic (Stretchy) because we're only talking a few percent expansion. Also, there can be telescoping segments rather than folding segments:

"With the help of an external energy source one of the rotors spins up to speed higher than the First Cosmic Velocity at sea level (i.e. orbital speed at sea level, same as the escape velocity divided by root two). Due to the centrifugal force, the rotor (having reached the First Cosmic Velocity) balances itself and then seeks to "fly" up, producing lift force. The rotor's speed is to be a little more than necessary to balance the ring.

After releasing the clamp the GPV ring begins to rise up (increasing its radius, and accordingly, the diameter). Thus, the hydraulic cylinders and gaps between the segments allow the formation to increase its length. The belt rotor stretches by 2-5% due to its elasticity."

Keep in mind, there can be fairly large gaps in the material with magnetic properties in track, as it whizzes by at over 8 km/second, a 10 meter telescoped section with no magetic material is only 0.00125 seconds of not being supported. x= 1/2 a*t^2, 1-2 earth's gravity is about 5 m/s/s, so 5* (0.00125)^2= 0.0000078125 meters, or 0.0078125 mm... the station won't fall more than 1/100th of a milimeter over such an expansion joint, and it would be well within the tolerances of the gap between the station and the track.

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So changing the speed of the cable will require that each of these two trains, drag half the weight of the entire structure?

Not weight, but mass... but yes, but the cable could be sped up or slowed down over the course of days. You could have 4 trains doing it (again, this system allows for a lot of redundancy). The system would probably be designed to operate in a narrow speed range anyway. I don't see much need to change the speed once you get it up there. So the change in momentum the trains need to handle is basically equal to that of the payloads that get launched+very minor drag losses on the ring.

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The construction of a normal elevator is simple, as you wrote, everything is a matter of appropriate material and it can be built. There are many complications in your idea and many things may fail.

Oh no its not!!!! the entire system is dynamically unstable until you get it anchored, and you can't anchor it until you finish it. All the material needs to start in space, which means launching massive amounts of complex material into space. You can't launch it all at once, and you've got at least 35,000km of material to join together (unless you can make a truly massive spool of cable, but then the ultra strong material also needs to be pretty flexible)

There are so many problems with getting a space elevator constructed. Meanwhile a ring can be entirely constructed on Earth, and spun up into space.

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Unless it was cut off on Earth? Then he should climb the orbit himself, because of the speed differences between the GSO and the surface of the planet?

If the break happened at the surface, then the system will get flung into an eliptical or hyperbolic escape orbit. Tension is highest at GSO, so a cable of uniform thickness would break there, causing 35,000 km of cable to come smashing down.

But then similarly, if a spoke-cable on a ring system is cut off at earth, nothing falls (but if its only got 2 stations, the ring-cable will become elliptical, with a high apoapsis, and a PE at the still attached station, which would then become unstable... but again, with multiple stations, you get redundancy). You're really reaching going for an unlikely best case scenario for the space elevator, which results in a complete loss of the space elevator.

If we do the same for the orbital ring, there's no damage to Earth, and the ring still operates, and the cable can be repaired.

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So the tensile strength of the cable can not be as large as you say. The counterweight on the GSO will pull up some of the cable's weight.

You seem to have a fundamental misunderstanding here. The entire elevator is in tension the counterweight/mass past GSO is pulling up the entire cable's weight.... not "some" of its weight.

Lifting 35,000 km of a cable (the entire length of cable going to slow to stay in an orbit at its altitude) is a lot of weight... which means A LOT of tension on the cable at GSO.

https://en.wikipedia.org/wiki/Specific_strength

"Another way to describe specific strength is breaking length, also known as self support length: the maximum length of a vertical column of the material (assuming a fixed cross-section) that could suspend its own weight when supported only at the top."

https://en.wikipedia.org/wiki/Space_elevator#Cable

" would need a material capable of sustaining a length of 4,960 kilometers (3,080 mi) of its own weight at sea level to reach a geostationary altitude of 35,786 km (22,236 mi) without yielding. "

Note the entry in the specific strength for carbon nano-tube, of 4716 ... too small so far... its followed by https://en.wikipedia.org/wiki/Colossal_carbon_tube

Which so far haven't been manufactured on anything but the microscopic scale, and we don't know how well they'd handle bending (if you want to use a spool of it during construction), or how much strength loss you'd lose at the macroscopic scale. Note that it seems a very daunting task to make a single carbon nanotube 35,000km long, so the full size cable would necessarily be weaker (due to the need for junctions and joining and such) than what has been measured for these single piece microscopic tubes.

[Cassel]

28 minutes ago, KerikBalm said:

https://en.wikipedia.org/wiki/Maglev

"The power needed for levitation is typically not a large percentage of the overall energy consumption of a high speed maglev system. Overcoming drag, which makes all land transport more energy intensive at higher speeds, takes up the most energy. Vactrain technology has been proposed as a means to overcome this limitation."

...
The ring does not need to be magnetic for the station to repel from the ring.
 

Where can I see this train live? Ohh no one built it, I wonder why.

Ok, the cable does not have to be made of magnets, this is probably the only thing that can work in this idea.
 

28 minutes ago, KerikBalm said:

No... well... that depends what height from the vertical space elevator it was ejected from. From the station of a ring, it would fall as if it had just been dropped from 300 km (assuming the ring is at 300 km). If something fell from a vertical space elevator, it could hit the ground at a velocity fairly close to escape velocity - depending how high up the vertical space elevator.
 

You do not understand many things, and you write as if this idea has already been implemented.
If you're writing a cable, you mean a flexible metal cable


So in my opinion, this concept is impossible to implement. The cable orbits at an altitude of 300-400 km, at the moment when your trains begin to slow down, gravity pulls them down to Earth. When they reach a speed equal to 0 km/h to the surface of the planet, while still at the height of 300km, the orbiting cable must hold train and cargo. And it is not important here the mass of the entire cable that you carried into orbit, only the part that is in contact with the train. The cable is flexible, right, so how will it behave?



Pull one of the cables attached to the planet, what will happen with cable-ring?
Of course, if the ring is made of metal and will be a rigid structure, then the force caused by the braking train will will spread over the entire structure.

Maybe it's worth to do a simple experiment and put a ring in something that floats (and resembles a cable, string maybe?) on the water in the aquarium, spin the ring, and then add the force that is directed to the center of the ring (this would be the braking train). How will the ring (string) behave?
 

28 minutes ago, KerikBalm said:

What you think, without math to back it up, is fairly irrelevant. Also keep in mind, its exactly centrifugal force that keeps a "classic" space elevator upright.
 

Here you make a mistake, it is mass of the counterweight keeps it upright.
In your example, at the moment of braking the train you would have to add a counterweight that pulls the train and cargo up and to prevent deformation of part of the ring.

28 minutes ago, KerikBalm said:

That case was for changing the altitude of the ring... and there doesn't need to be a foldered cable. It could simply be elastic (Stretchy) because we're only talking a few percent expansion. Also, there can be telescoping segments rather than folding segments:

 

Flexible/elastic cable - no. Telescopic rigid construction - yes.
 

28 minutes ago, KerikBalm said:

Not weight, but mass... but yes, but the cable could be sped up or slowed down over the course of days. You could have 4 trains doing it (again, this system allows for a lot of redundancy). The system would probably be designed to operate in a narrow speed range anyway. I don't see much need to change the speed once you get it up there. So the change in momentum the trains need to handle is basically equal to that of the payloads that get launched+very minor drag losses on the ring.
 

Is this a joke? So, bringing the cargo into orbit and the fact that the train stopped in relation to Earth, and later repelled itself from the cable, do you think it will not change the orbit of the flexible ring and it will still be in the same orbit?

In my opinion, there will be a change in the cable's orbit, something similar to the tehter's orbit in the image below.

28 minutes ago, KerikBalm said:

Oh no its not!!!! the entire system is dynamically unstable until you get it anchored, and you can't anchor it until you finish it. All the material needs to start in space, which means launching massive amounts of complex material into space. You can't launch it all at once, and you've got at least 35,000km of material to join together (unless you can make a truly massive spool of cable, but then the ultra strong material also needs to be pretty flexible)

 

In the case of space-elevator, you can connect the cable with segments, even starting from the Earth. Only you would have to start with a very light construction, you do not have to reach the GSO in first step, but at the end of cable you would have to put a vehicle with an ion engine that would move a little faster than the cable in a given orbit and would pull the cable behind it.
The next stage is the addition of further fragments of cables up to GSO and counterweight. If the cable is thin as a climbing rope, the counterweight does not have to be large.
The next step is to pull up the next connections and appropriate counterweight on the GSO.
I know that you imagine a space-elevator as one big cable, but for safety there can be many cables. Over time, as better materials will be created, you can always pull cables with a larger cross-section using this small infrastructure.

 

28 minutes ago, KerikBalm said:

You seem to have a fundamental misunderstanding here. The entire elevator is in tension the counterweight/mass past GSO is pulling up the entire cable's weight.... not "some" of its weight.
 

 

Maybe, I have not thought about this concept before.

But I see that you completely ignore the fact that in your idea when you pull up a cargo from the surface of the planet you also need a counterweight or some force that will keep your train in orbit.