Space Elevator

[gilbertsmith]

Hi Everyone, Instead of building a ribbon or a rope from nano strings to make a space elevator. Wouldnt it better to construct a tube and the build a tubeular space craft to travel inside the tube. We would need to create a partial vacum inside the tube to lesson force of gravity on the craft as, it travels up the tube. Does anyone think this is possible?

 

 

 

 

(mod note: moved to general physics)

[timo]

The force due to gravity is unchanged in vacuum. You still have the same problems for building a long vertical tube as you have for building a long vertical tower when it comes to the stress on the material.

[insane_alien]

all thats going to mean is that you have a more expensive elevator.

[Mr Skeptic]

Making it a large, rigid, airtight tube would just be unfeasable.

[gilbertsmith]

Hi Everyone, Instead of building a ribbon or a rope from nano strings to make a space elevator. Wouldnt it better to construct a tube and the build a tubeular space craft to travel inside the tube. We would need to create a partial vacum inside the tube to lesson force of gravity on the craft as, it travels up the tube. Does anyone think this is possible?

Thanks for you for the replies. So, how does a vacum tube work?

[insane_alien]

are you thinking of pneumatic tubes?

 

because a vacuum tube is a primitive version of the transistor.

 

if you are thinking of pneumatic tubes then they work by using a pressure differential to move the canisters. they do not affect the force of gravity in any way.

[Hidemons]

Wait, answer the question though! I pretty sure gilbert meant Pneumatic tubes. I thought the hardest part of that Japanese Elevator is finding the right material for the cables. I read an article that said that those proposed nanotubes have to 5x stronger than they are right now to work.

 

What is inefficient or bad about a Pneumatic elevator idea? The fact that the elevator tube has to be forever leak proof?

[Mr Skeptic]

What is inefficient or bad about a Pneumatic elevator idea? The fact that the elevator tube has to be forever leak proof?

 

The problem is that that much air is absurdly heavy. Compressed air is even heavier. On the other hand, using a vacuum at the top won't work because there already is a vacuum on the top (plus, then you would need the elevator to have compressive strength as well as the easier tensile strength). In both cases, leakproofing the thing would be absurdly heavy. The biggest problem with the space elevator is that it must be built of a material strong and light enough, so any extra weight is out of the question.

[Hidemons]

The problem is that that much air is absurdly heavy. Compressed air is even heavier. On the other hand, using a vacuum at the top won't work because there already is a vacuum on the top (plus, then you would need the elevator to have compressive strength as well as the easier tensile strength). In both cases, leakproofing the thing would be absurdly heavy. The biggest problem with the space elevator is that it must be built of a material strong and light enough, so any extra weight is out of the question.

 

 

You inadvertently presented an interesting idea there. There is a natural vacuum coming from space. This means that if the japanese figured out a method already for creating a structure tall enough to reach space then pressure differences could be used to lift the elevator box. Then once the elevator has reached the top of the structure, to go down, the top of the structure could be covered up and re-pressurized normally to get the elevator box to go down. It's like reverse gravity.

 

Also, is making the elevator box strong enough to handle the pressure really that big of a deal?

The leak-proofing is the biggest problem with the weight of the whole thing inevitably being ridiculous but I'm not sure what the people legitimately trying to design the elevator shaft are thinking how to create it anyway. so.

Edited May 8, 2009 by Hidemons

[J.C.MacSwell]

You inadvertently presented an interesting idea there. There is a natural vacuum coming from space. This means that if the japanese figured out a method already for creating a structure tall enough to reach space then pressure differences could be used to lift the elevator box. Then once the elevator has reached the top of the structure, to go down, the top of the structure could be covered up and re-pressurized normally to get the elevator box to go down. It's like reverse gravity.

 

Also, is making the elevator box strong enough to handle the pressure really that big of a deal?

The leak-proofing is the biggest problem with the weight of the whole thing inevitably being ridiculous but I'm not sure what the people legitimately trying to design the elevator shaft are thinking how to create it anyway. so.

 

Seems somewhat like a lock in a canal using air instead of water, and somewhat like a human cannon.

 

Making it strong enough to handle internal pressure would be relatively easy. Supporting a tower that high would be one amazing feat of engineering.

[GDG]

You inadvertently presented an interesting idea there. There is a natural vacuum coming from space. This means that if the japanese figured out a method already for creating a structure tall enough to reach space then pressure differences could be used to lift the elevator box. Then once the elevator has reached the top of the structure, to go down, the top of the structure could be covered up and re-pressurized normally to get the elevator box to go down. It's like reverse gravity.

 

Remember, the atmosphere is already "open to space at the top". To get any usable pressure difference, you would have to evacuate the shaft above the elevator (and use a very light-weight elevator). To loft the elevator all the way to the top, you would need to pressurize the shaft below it. Considerably.

[Ophiolite]

The elevator would be approximately 35,000km long. There is practically no atmosphere above 100km. So you are debating a major design change that would be relevant for less than 0.3% of the elevator.