How would a space elevator be built?

[Cloakedwand72]

So Boeing invented a new materiel with 99.99% air and as seen in this video

And could this be used for a crewed space elevator?And how would the space elevator cable be deployed form the ground or from the orbiting space elevator module?Is this even possible in real life and or in KSP?

[Laie]

The only method I'm aware of would require all material to be brought to geostationary orbit, and deployed in both directions from there.

Keep in mind that we're talking about a lot of stuff here. That string would need to be like quite long, like twice around the equator long, and hundreds to thousands of meters wide. If all that matter was plain old dirt, you'd need to excavate the whole of Lybia or Texas down to sea level.

I can't see how we would could even begin that task in my lifetime. The least incredible way I can think of would be to develop a lot of in-space infrastructure and to harvest asteroids for raw material and the fuel to move it.

[andrewas]

Step one is to create a material strong enough to build a tether with a reasonable mass. Our best tensile materials aren't up to the job, but carbon nanotubes and a few others would do it if they could be produced in bulk.

From there, you extrude a few kilometres of it in geostationary orbit, use gravity gradient stabilization and thrusters to orient it verticallys, and extruded more cable to raise the counterweight as you drop the lower end. Once you have a single tether, you can begin to move manufacturing equipment and raw materials up to the base station for a few dollars a kilo, so expanding the system is much easier than building that first tether.

Oh, I forgot step 2 - arrangement everything below LEO so it won't hit the cable. Deorbit the junk, consolidate the satellites into as few platforms as possible, adjust every orbit so it's in resonance with the cable and won't hit it. This bit is possibly harder than actually deploying the tether.

Edited November 14, 2015 by andrewas

[Streetwind]

This video here gives you a rough idea how a space Elevator would be constructed. Okay, this one's on the Moon, where it is feasible to do with today's technology, and not on Earth, where it is not feasible. But the basic principles are still there: Set up a geostationary orbiting module, get a light tether to the ground, and then use robots climbing along that tether to strengthen it by adding more and more fibers over time, increasing the payload the elevator can handle.

[Bill Phil]

The problem with a space elevator is that it's not really practical, and is also fantastical. When it does become practical, there will most likely be other technologies that are even better for surface to orbit operations.

[SpaceXray]

That string would need to be like quite long, like twice around the equator long, and hundreds to thousands of meters wide.

xD I cracked up there, sorry. You mean LONG, not wide.

The main problem, as already mentioned, is making an extremely long wire(35800km long), which would be made out of a very durable material and lightweight at the same time. Now, the best option is to produce it in geostationary orbit and lower it down, and produce the counterweight part of it there too.

Now for the materials. They would either have to be supplied from the Moon or we would have to get a few asteroids and create the cable by using the resources from them.

All we have to do is learn to make this material(carbon nanotubes probably), be able to catch asteroids easily and mine them, as well as learn to set up large-scale manufacturing in space.

At first, the main task is to make the wire, then make it thicker as more of it's use is required.

[Bill Phil]

xD I cracked up there, sorry. You mean LONG, not wide.

Oh no, he meant wide. It needs to be, otherwise it would just snap and break, trillions wasted.

Also, if it's a few thousand meters long, it's not a space elevator. It's a building. It needs to be thousands of kilometers long. Hundreds of METERs wide.

[Laie]

The main problem, as already mentioned, is making an extremely long wire(35800km long),

...plus again at least half as much for the counterweight. And that "wire" would need to be quite thick even to begin with. I was not joking.

All we have to do is learn to make this material(carbon nanotubes probably), be able to catch asteroids easily and mine them, as well as learn to set up large-scale manufacturing in space.

I'm afraid you underestimate the scope of the task. Peace on earth and a happy life for everyone is easy in comparison.

[Findthepin1]

The cable doesn't need to be very wide. Perhaps tens of metres. The width is about how much weight it's pulling around at a time. It's like, water in a kilometre-tall glass has the same bottom pressure as under kilometre-deep seafloor. It doesn't count the influence of whatever's beside it, only above and below.

On a side note, IMO the best place to put a space elevator on Earth is the Andes in Ecuador. On Mars would be Pavonis. Both locations have much thinner air and are smack-dab on the equator.

- - - Updated - - -

The cable doesn't need to be very wide. Perhaps tens of metres. The width is about how much weight it's pulling around at a time. It's like, water in a kilometre-tall glass has the same bottom pressure as under kilometre-deep seafloor. It doesn't count the influence of whatever's beside it, only above and below.

On a side note, IMO the best place to put a space elevator on Earth is the Andes in Ecuador. On Mars would be Pavonis. Both locations have much thinner air and are smack-dab on the equator.

[PB666]

Suppose we had the mats, we don't and carbon nanotubes are not strong enough.

The composite tether and platforms center of mass would have to be at GSO, since the tether is quite heavy the platform itself would be above point mass GSO. This creates a problem for any equitorial orbiter above and below GSO and increases the risk greatly, like 1000 fold relative to mass of a collision with any orbiter below the platform that crosses the equator. What if the tether was perfectly thin, it matters half as much as you think, the ISS is a footbal field long, so theres a good chance at some point it would crop the cable at 300 miles up.

So we equip the cable with episodic manuevering jets.

Next is power, this appears to be benign problem it is not, if you send voltage from the earth to the platform, you have to send it back, round trip is 60,000. That only works with a super conductor, and we dont have any that work at ambient temperatures. The alternative is a very high voltage high frequency ultrathin wire, the problem is that the neutral is close a power is lost due to ionization of gas aound the wire, which btw happens in space withou 100kv voltage differential. In either case the insulation on the wire has to be probitively heavy.

OK so the carraige has to be solar powered as such it will be traction driven. Lets say the panel is 1M^2 and it has only to lift 100 kg, a man and his life support, so a perfect panel is 1KW

E joules = force times distance = N * M, so to lift 100 kg 1 meter =mgh = 100 * 9.8 so at best you are lifting 1 m/s. But its actually worse since solar efficiency is a third, and thus you would actually be falling backwards unless the device is regeared to get about 0.25 meters per second, at least for the first 4000 miles. This means the carraige should also carry a battery, which means it stores power, lurches up 100 feet and then rests while it recharges. Alternatively it needs several square meters of solar panels that increase weight.

The next problem is life support, your rider is now going to be in the carraige for half a day, he will essentially need an EVA suit as the carraige. So that is going to double the weight and then the solar panels.

So now we return to the cable, which now has to support about 300 kg in panels, personell, and life support, it needs a tractor, to work friction needs both pressure and surface area, that perfectly thin wire aint going to cut it. So add some sort of replaceable coating the can wear under traction, this means that the cable itself has to be wide orthe tractor has to be long and heavy. But if the cable has to be wide and coated then the platform needs a larger balast mass and it then becomes impracticle.

[Bill Phil]

The cable doesn't need to be very wide. Perhaps tens of metres. The width is about how much weight it's pulling around at a time. It's like, water in a kilometre-tall glass has the same bottom pressure as under kilometre-deep seafloor. It doesn't count the influence of whatever's beside it, only above and below.

On a side note, IMO the best place to put a space elevator on Earth is the Andes in Ecuador. On Mars would be Pavonis. Both locations have much thinner air and are smack-dab on the equator.

However, even if we use carbon nanotubes, their compression strength is probably not enough for the ground levels. I don't know exactly, but let's say it is. How much surface area is required to hold up the weight of the entire elevator? Looking at how much pressure per unit of area. Definitely enough for at least a hundred meters width at the base if it's a circle.

The pressure is what matters, but water in a 30,000 kilometer tall glass would have enormous pressures at the bottom, so more surface area and structural members would have to be added so the glass doesn't shatter.

The cable needs to be supported, and it has a huge mass and a huge weight, resulting in a huge, pyramid-like structure near the bottom. Why a pyramid? It's one of the most stable types of structures there is.

[Rakaydos]

However, even if we use carbon nanotubes, their compression strength is probably not enough for the ground levels. I don't know exactly, but let's say it is. How much surface area is required to hold up the weight of the entire elevator? Looking at how much pressure per unit of area. Definitely enough for at least a hundred meters width at the base if it's a circle.

The pressure is what matters, but water in a 30,000 kilometer tall glass would have enormous pressures at the bottom, so more surface area and structural members would have to be added so the glass doesn't shatter.

The cable needs to be supported, and it has a huge mass and a huge weight, resulting in a huge, pyramid-like structure near the bottom. Why a pyramid? It's one of the most stable types of structures there is.

You're thinking stalagmite type structure (thicker at the bottom) instead of the proposed stalagtite type structure (thicker at the top). By relying on tensile stength instead of compressive strength, they take advantage of microgravity to reduce the effective weight of the most masive parts of the cable.

I believe an earth-geosynch elevator is at least a century away. However, I believe a Moon-Lagrange elevator (either nearside to L1 or farside to L2) will be the first built, and a Mars-Demos elevator is almost half built already.

[fredinno]

The cable doesn't need to be very wide. Perhaps tens of metres. The width is about how much weight it's pulling around at a time. It's like, water in a kilometre-tall glass has the same bottom pressure as under kilometre-deep seafloor. It doesn't count the influence of whatever's beside it, only above and below.

On a side note, IMO the best place to put a space elevator on Earth is the Andes in Ecuador. On Mars would be Pavonis. Both locations have much thinner air and are smack-dab on the equator.

- - - Updated - - -

The cable doesn't need to be very wide. Perhaps tens of metres. The width is about how much weight it's pulling around at a time. It's like, water in a kilometre-tall glass has the same bottom pressure as under kilometre-deep seafloor. It doesn't count the influence of whatever's beside it, only above and below.

On a side note, IMO the best place to put a space elevator on Earth is the Andes in Ecuador. On Mars would be Pavonis. Both locations have much thinner air and are smack-dab on the equator.

It would need to be on the ocean, so that it could move in the case of small pertubations.

- - - Updated - - -

You're thinking stalagmite type structure (thicker at the bottom) instead of the proposed stalagtite type structure (thicker at the top). By relying on tensile stength instead of compressive strength, they take advantage of microgravity to reduce the effective weight of the most masive parts of the cable.

I believe an earth-geosynch elevator is at least a century away. However, I believe a Moon-Lagrange elevator (either nearside to L1 or farside to L2) will be the first built, and a Mars-Demos elevator is almost half built already.

But those won't be practical for at least the next two centuries to have.

[Bill Phil]

You're thinking stalagmite type structure (thicker at the bottom) instead of the proposed stalagtite type structure (thicker at the top). By relying on tensile stength instead of compressive strength, they take advantage of microgravity to reduce the effective weight of the most masive parts of the cable.

I believe an earth-geosynch elevator is at least a century away. However, I believe a Moon-Lagrange elevator (either nearside to L1 or farside to L2) will be the first built, and a Mars-Demos elevator is almost half built already.

You still have to support the weight, though. Sure, it's not as much as the mass, as the gravity changes, but it needs to be supported.

[Rakaydos]

But those won't be practical for at least the next two centuries to have.

I disagree- a lunar elevator would cause a boom in lunar explloiation, by reducing the DV cost to reach the lunar surface by at least a third, and reduce lunar material launch DV costs to nothing. (3.77 KM/s vs 5.93 KM/s)https://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space.E2.80.94high_thrust

- - - Updated - - -

You still have to support the weight, though. Sure, it's not as much as the mass, as the gravity changes, but it needs to be supported.

yes, but it's supported from ABOVE, not below. the counterweight lifts 100.00000...1% of the cable's mass away from earth, and the cable is tied down to keep the counterweight from flying away.

[Bill Phil]

I disagree- a lunar elevator would cause a boom in lunar explloiation, by reducing the DV cost to reach the lunar surface by at least a third, and reduce lunar material launch DV costs to nothing. (3.77 KM/s vs 5.93 KM/s)https://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space.E2.80.94high_thrust

- - - Updated - - -

yes, but it's supported from ABOVE, not below. the counterweight lifts 100.00000...1% of the cable's mass away from earth, and the cable is tied down to keep the counterweight from flying away.

The counterweight can't support all of it. It's not possible, especially closer to the Earth. You still need stuff.

[fredinno]

I disagree- a lunar elevator would cause a boom in lunar explloiation, by reducing the DV cost to reach the lunar surface by at least a third, and reduce lunar material launch DV costs to nothing. (3.77 KM/s vs 5.93 KM/s)https://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space.E2.80.94high_thrust

- - - Updated - - -

yes, but it's supported from ABOVE, not below. the counterweight lifts 100.00000...1% of the cable's mass away from earth, and the cable is tied down to keep the counterweight from flying away.

But the start-up costs would make it impossible until there is at least a sizable colony there.

[Rakaydos]

The counterweight can't support all of it. It's not possible, especially closer to the Earth. You still need stuff.

citation needed.

A counterweight CAN support all of it, simply by moving faster than orbital velocity. (that is, circling the globe in 24 hours when beyond geosynchronus orbit)

If the counterweight needs to counter more weight, either make it bigger or stick it in a higher orbit- this scales up until the counterweight starts actually interfereing in the Earth Moon system. A space elevator will hoave nowhere NEAR -that- kind of mass requirement.

[Bill Phil]

citation needed.

A counterweight CAN support all of it, simply by moving faster than orbital velocity. (that is, circling the globe in 24 hours when beyond geosynchronus orbit)

If the counterweight needs to counter more weight, either make it bigger or stick it in a higher orbit- this scales up until the counterweight starts actually interfereing in the Earth Moon system. A space elevator will hoave nowhere NEAR -that- kind of mass requirement.

It can't support it all, since there are structures near the surface.

But beyond that, what supports the force of the counterweight pulling it away? According to you it's a thin cord, when it would actually be a large structure. After all, it's still supporting it, just from the opposite direction.

[Rakaydos]

It can't support it all, since there are structures near the surface.

But beyond that, what supports the force of the counterweight pulling it away? According to you it's a thin cord, when it would actually be a large structure. After all, it's still supporting it, just from the opposite direction.

Again, citation needed. All I'm seeing are unsupported assertations. Why must there be "structures" near the surface? Why would the cord lave to be a large structure?

[Bill Phil]

Again, citation needed. All I'm seeing are unsupported assertations. Why must there be "structures" near the surface? Why would the cord lave to be a large structure?

Centripetal force. When you spin things, they provide a force going outward from the center. If you don't want millions of tonnes flying off, you have to ground it. And since it's millions of tonnes, with v^2/r, you need lots of structural pieces so it doesn't fly off from Earth.

The math depends on where the counterweight is, the mass of the elevator.

You can use a=V^2/r to find the acceleration, and then multiply by the mass of the counterweight to find the force of the counterweight from centripetal acceleration, and you would have to do this over the whole elevator to find it at various radii.

Edited November 15, 2015 by Bill Phil

[Kerbart]

Next is power, this appears to be benign problem it is not, if you send voltage from the earth to the platform, you have to send it back, round trip is 60,000. That only works with a super conductor, and we dont have any that work at ambient temperatures.(...) OK so the carraige has to be solar powered as such it will be traction driven.

If you assume we have the materials it's also safe to assume we have the technology to transmit power wireless. Laser beams, microwaves, etc. The elevator doesn't move very fast, along a known trajectory, so it's easy to aim the power beam.

[Rakaydos]

Centripetal force. When you spin things, they provide a force going outward from the center. If you don't want millions of tonnes flying off, you have to ground it. And since it's millions of tonnes, with v^2/r, you need lots of structural pieces so it doesn't fly off from Earth.

The math depends on where the counterweight is, the mass of the elevator.

You can use a=V^2/r to find the acceleration, and then multiply by the mass of the counterweight to find the force of the counterweight from centripetal acceleration, and you would have to do this over the whole elevator to find it at various radii.

And there will be a point where the outward centripedial acceleration of the counterweight and elevator exactly matches the inward gravitational weight of said counterweight and elevator. Canceling these two forces out, the weight on the ground is nil, the only concern is th structure's tensile strength, to hold together through that much dynamic tension.

Edited November 15, 2015 by Rakaydos

[PB666]

If you assume we have the materials it's also safe to assume we have the technology to transmit power wireless. Laser beams, microwaves, etc. The elevator doesn't move very fast, along a known trajectory, so it's easy to aim the power beam.

This sounds like another Star Trekism. Laser beams and carbon-whatever cable, nope. microwves pointed at your scantly protected naut or cable, nope. Microwvae to energy conversion is heavy. The cable passes into the stratosphere are certainly blowing around in the 10 s of meters per second winds that blow around thus it is certainly not stationary. Again lets take the sci-fi mentality out of the science.

If you have away to make things of mass nearly weightless, e.g. the cable, and increase energy densities 100 fold over present levels, guess what, you don't need a cable, you have a super efficient rocket that can reach its target much more cheaply.

[Bill Phil]

And there will be a point where the outward centripedial acceleration of the counterweight and elevator exactly matches the inward gravitational weight of said counterweight and elevator. Canceling these two forces out, the weight on the ground is nil.

What's the estimated mass of the counterweight? Let's say it's a few thousand tonnes. Being nice here. That's about 2 million kilograms. Let's say the counterweight is at twice the distance of GEO(which is at about 35786 kilometers). Then we'll use the orbital velocity at GEO, since it has to be moving that fast. About 3070 m/s. Square that... you get 9424900. Then you divide by 35786, then 2. This is basically doubling the number we're dividing by. The acceleration on the counterweight is about 132 meters per second squared. Compared to Earth sea level gravity and the gravity at 2*GEO, it's way too big. The force then, would be 2 million kilograms times ~132 m/s^2. Which is about 263368456.3 Newtons on the counterweight. This is felt by the structure on the ground, plus the weight of the material from the ground to the counterweight. And that's assuming the counterweight is 2000 tonnes.

The gravity at 2* GEO altitude is 1/4 of GEO altitude, it doesn't counteract it.

It's actually technically negative weight, compared to the Earth's center. It goes away from Earth. But that's the reference frame of Earth, and it's not even really possible to be negative, but...

This thing will fly off into oblivion, and wreak havoc, unless you have facilities on the ground to account for it.

Now, the acceleration at 2*GEO is 1/(2*35786000/6371000)^2

Actually, wait, that's in kilometers. Whatever, disregard. Give me a sec.

Yeah, divide the acceleration and force by 1000. Kilometers to meters and such.

The acceleration is low, but there is still the force to look at. It's not huge, but it's there. And then you have the mass of the whole elevator to take into account.

Edited November 15, 2015 by Bill Phil