# Revolutionizing Space Travel: The Potential of Dual Space Elevators

• FXForLife
In summary, the conversation discusses the idea of using two space elevators on opposite sides of the Earth connected by a cable on the ground in order to reduce the payload on the cable and make it feasible to use traditional materials. However, it is pointed out that this would not solve the main problem of creating a cable that can support its own weight below geostationary orbit and would instead create a larger engineering challenge. The idea is ultimately deemed not feasible.
FXForLife
Hello

I am new to thinking about these kinds of things so please forgive me if what I suggest is pure nonsense LOL!

As I understand it the main problem with building the traditional model of a space elevator is a practical one based on the difficulty in manufacturing a cable made of nanocarbon which can support its own weight below geostationary orbit.

Perhaps there is a way around this. Perhaps we can develop a model which reduces, or nearly eliminates the payload on the cable.

If we were to build 2 space elevators, one on either side of the Earth in perfect balance, with a land and ocean based cable circling the Earth and connecting the two, wouldn't that neutralize the payload on the cable? That way we could possibly construct the cable out of more traditional materials, like kevlar??

Thanks

How would that neutralize the payload? Gravity is pulling down. A cable pulling sideways would not help anything. And I don't think you appreciate how big the Earth it. A cable long enough to go all the way around the Earth to connect two elevators in the air would sag till it touched the Earth and snap under its own weight in the process.

chrisbaird said:
How would that neutralize the payload? Gravity is pulling down. A cable pulling sideways would not help anything. And I don't think you appreciate how big the Earth it. A cable long enough to go all the way around the Earth to connect two elevators in the air would sag till it touched the Earth and snap under its own weight in the process.

Thanks very much for the reply.

I was thinking the two space elevators would be exactly opposite from each other, on either ends of the Earth so that the effects of gravity and centrifugal force would be in equilibrium.

The cable would wrap around the Earth on the ground, not in the air and shouldn't snap due to the equilibrium of the system (I'm trying my best here lol). If the circumference of the Earth is 40,000 km we would be adding, from what I understand, about 20% more cable, which, if made out of something other than carbon nanotubes, might very well be feasible.

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Welcome to PF!

In equilibrium may mean all forces sum to zero, but it doesn't mean the forces go away. A space elevator would on its own be in a similar equilibrium to what you describe.

russ_watters said:
Welcome to PF!

In equilibrium may mean all forces sum to zero, but it doesn't mean the forces go away. A space elevator would on its own be in a similar equilibrium to what you describe.

If I understand correctly a space elevator on its own would still require a cable that could support its own weight below geostationary orbit.

But if you have two counterweights on opposite sides of the Earth, out in space, connected, then this is no longer an issue and a cable can be made of more typical materials.

thanks for the welcome btw!

Here are some diagrams to help explain my thinking:

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Oh, we understand your way of thinking alright. What we are telling you is that you are "solving" a little problem by making a bigger one.

I suppose if problem A is solvable in 100 years and problem B is solvable in 10, then problem b would be smaller.

FXForLife said:
I suppose if problem A is solvable in 100 years and problem B is solvable in 10, then problem b would be smaller.

Problem B is not solvable in 10 years. It's even more of an engineering challenge than a single elevator.

If you have 2 equal teams playing tug-of-war the forces on the rope are equal and opposite so the total force on the rope is zero. That's why the rope does not move. That does not mean that the tension on the rope is zero. The situation you are describing is similar. The problem with building a space elevator is making a rope that will withstand the tension.

mrspeedybob said:
If you have 2 equal teams playing tug-of-war the forces on the rope are equal and opposite so the total force on the rope is zero. That's why the rope does not move. That does not mean that the tension on the rope is zero. The situation you are describing is similar. The problem with building a space elevator is making a rope that will withstand the tension.

OK but the main difference here is that the counterweights are in a fixed orbit in space around the Eath and therefore they don't pull very much on the cable, they simply keep it in place.

Drakkith said:
Problem B is not solvable in 10 years. It's even more of an engineering challenge than a single elevator.

Why?

FXForLife said:
OK but the main difference here is that the counterweights are in a fixed orbit in space around the Eath and therefore they don't pull very much on the cable, they simply keep it in place.

The only difference is the useless rope around the world.

DrStupid said:
The only difference is the useless rope around the world.

*carry the 2 LOL!

FXForLife said:
OK but the main difference here is that the counterweights are in a fixed orbit in space around the Eath and therefore they don't pull very much on the cable, they simply keep it in place.

Each tether still has its own mass and, hence, its own weight which needs to be supported by the tension in the rope. This applies however many tethers are involved and is the reason why the space elevator is not yet doable.

FXForLife said:
OK but the main difference here is that the counterweights are in a fixed orbit in space around the Eath and therefore they don't pull very much on the cable, they simply keep it in place.
This simply isn't true. In both cases, the counterweights support exactly the same weight: The weight of the cable from the counterweight to the ground. Your case has the added issue of a cable around the Earth that since it is parallel to the Earth's surface is supporting no weight at all. The added piece of your idea doesn't actually do anything at all.
FXForLife said:
*carry the 2 LOL!
Uh huh...in that cable around the earth, where it meets the space elevator: what direction is the force on the space elevator? Up or down?

mrspeedybob said:
If you have 2 equal teams playing tug-of-war the forces on the rope are equal and opposite so the total force on the rope is zero. That's why the rope does not move. That does not mean that the tension on the rope is zero. The situation you are describing is similar. The problem with building a space elevator is making a rope that will withstand the tension.

What if we drill a hole through the Earth? Would that help anything?

FXForLife said:
What if we drill a hole through the Earth? Would that help anything?

No, because the outer core is very hot and molten. Nothing is going to survive going through there, and the inner core is solid nickel / iron you ain't going to drill through that

Dave

FXForLife said:
What if we drill a hole through the Earth? Would that help anything?

Layering impractical idea upon impractical idea will not lead to a solution. It also pretty much defines "overly speculative".

## 1. What exactly is a dual space elevator?

A dual space elevator is a proposed concept for revolutionizing space travel by using two space elevators that are connected at the top and bottom ends. This means that instead of one long elevator extending from Earth's surface to outer space, there would be two shorter elevators connected by a horizontal platform.

## 2. How would a dual space elevator work?

The dual space elevator would consist of two main components - the elevators themselves and the horizontal platform connecting them. The elevators would be anchored to the Earth's surface and extend up into orbit, while the platform would be suspended in space between the two elevators. Spacecrafts would dock at the platform and then travel up or down the elevators to reach their desired destination.

## 3. What are the potential benefits of a dual space elevator?

A dual space elevator has the potential to greatly reduce the cost and time of space travel. By having two shorter elevators instead of one long one, it would be easier to construct and maintain. It could also allow for more frequent and efficient launches, as multiple spacecrafts could dock at the platform at the same time. Additionally, the reduced cost of space travel could make it more accessible to a wider range of people and industries.

## 4. What are the challenges of implementing a dual space elevator?

One of the main challenges is the construction of such a large and complex structure. The materials and technology needed to build a dual space elevator are still being developed and tested. There are also concerns about the safety and stability of the elevators and platform, as well as the potential impact on the environment.

## 5. Is a dual space elevator a realistic possibility?

While the concept of a dual space elevator is still in the early stages of development, many experts believe that it is a realistic possibility in the future. With ongoing advancements in technology and materials, it is possible that a dual space elevator could become a viable option for space travel and exploration.

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