Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

GCNRevenger · 2004-11-22 18:32:05

Oh really Errorist? Why? Because "you think so?"

ERRORIST · 2004-11-22 19:20:36

No because Dr. Spocks logic tells me so. If you introduce a gas into a cylinder and the cylinders altitude is X amount then the higher in altitude that gas is pumped into that cylinder then the gravity holding that gas down gets less. So depending on whatever pressure you introduce that gas at will determine the altitude it will reach. It is proportional to pressure and altitude. IT WILL ALSO FLOW TO AN AREA OF LOWER PRESSURE WHICH IS WHERE THE OTHER END OF THE U TUBE IS.

GCNRevenger · 2004-11-22 21:46:10

no errorist

no it won't

Gravity will pull the gas back down no matter how hard you pull on it with a low pressure region. Space is the ultimate low pressure region, and it is right over our atmosphere... why doesn't our atmosphere get sucked away?

Gravity affects all thing, all things, big or small... planets, moons, rocks, and yes - gas molecules. Gas molecules cannot travel faster then 3.0km/sec without getting too hot, and that is not fast enough.

No amount of pulling or sucking or whatnot you can do, syphon pump or whatever, will ever fix this.

Austin Stanley · 2004-11-22 22:09:21

Aghh... you are making me want to pull my hair out.

When you are dealing with such large distances and amounts there are more factors to deal with than simple PV=nRT.

I think GCN tried to point this out to you before, but I'll try and beat it into your head again.

Space is a vacume, correct? And earth has an atmosphere at (comparitivly) high pressure. So why then does not all our atmosphere run-off to space, a region of low pressure? Because of gravity of course. Earth has heck of alot of gravity which keeps out atmosphere from flying off. Which is convient, because I like to breathe.

That is the same reason you can't have a "manometer" that goes all the way up to oribt. It simply wont work. And even if it did, you would have achived nothing for it. A 50,000km trip, up and down, for no point.

Here are a couple expirment you can do at home to prove it. First find a short length of tube and two containers for water. Fill one up with water and place it about a foot above the other one. Now suck through the tube until water comes out and place it in the other container, viola! A siphon.

Now, after staring in amazment for a while, lift the lower container up above the level of the higher container... and look, the siphon has stoped. Repeat the expirment all you want with any variation you care, the results will always be the same.

For a secound expirment you would require a garden hose, and a roof. Place your two bucket as before (they should probably be bigger this time), and suck on the hose to start the siphon. Now, climb up on the roof and then drag the middle of the hose up with you. After you have rasied the middle up 10meters (hmm, maybe a two-story house), the siphon will stop. Anyway you repate this the results will be the same. Your plan will NEVER work.

ERRORIST · 2004-11-22 22:39:17

I think you guys are getting the U tube concept out of wack here. First off the bend in the upside down U tube is never exposed to the vacuum of space. It only turns back down through the atmosphere to 1000 feet above sea level The other end is a few feet above sea level. Now tell me how the vacuum gets into the pipe if both ends are open to atmosphere and no holes are in it?

GraemeSkinner · 2004-11-22 22:47:35

Again, you ignore the compressability of gasses. If you pump more gas up, then all you get is high pressure, not proportionally taller height.

If you keep increasing the pressure at the bottom, you'd also have to increase the strength of the tube or it'll just fly apart. By the time the tube was strong enough to take the amount of pressure required it would be far from a nano-anything. The tube would also have to be insulated or it would have difficulties transferring anything in quantity at 190K (degrees kelvin). Our atmosphere has a large range of temperatures that would create a lot of problems if the tube was possible.

Graeme

GCNRevenger · 2004-11-22 22:49:45

Errorist, will you PLEASE think for once!

THINK! Just STOP and THINK for a minute

There is no "vacuum that gets into the tube" like some kind of contaminant... you don't even know how a syphon works!

ERRORIST · 2004-11-22 22:50:11

Now you introduce an after cooler for the air compressor to cool the air before letting it in the tube.

GraemeSkinner · 2004-11-22 22:52:55

Now you introduce an after cooler for the air compressor to cool the air before letting it in the tube.

You want it colder than 190K ?

Graeme

ERRORIST · 2004-11-22 23:18:19

Oops I was thinking F

GCNRevenger · 2004-11-22 23:29:02

I think you guys are getting the U tube concept out of wack here. First off the bend in the upside down U tube is never exposed to the vacuum of space. It only turns back down through the atmosphere to 1000 feet above sea level The other end is a few feet above sea level. Now tell me how the vacuum gets into the pipe if both ends are open to atmosphere and no holes are in it?

*holds his head and trys to collect himself*

Because the force of gravity is SO strong here on Earth, it will pull down any gas or fluid in both sides down. BOTH of them. So there won't be anything left at the top. We call this a "vacuum."

The force of gravity pulling down two columns 36,000km tall is WAY more then enough to break any miniscule cohesive forces between liquids.

ERRORIST · 2004-11-22 23:42:56

So which side will empty out first?

GCNRevenger · 2004-11-22 23:44:54

Why does it matter? The stuff you want to move is falling down, its not going up.

Shaun Barrett · 2004-11-23 02:16:19

Hi ERRORIST.
GCNRevenger is quite correct, I'm afraid, and so is Austin Stanley. An inverted U-shaped tube won't work as a siphon at anything near the lengths you have in mind.
What drives the siphon effect we're all familiar with is the weight of the atmosphere pushing down on the surface of the liquid you're trying to siphon.
Suppose you wish to remove water from Container A and place it in Container B. Obviously, you put one end of a rubber hose (or similar) into the water in Container A and place the other end - lower than the water surface in A - over the open top of Container B. You suck the open end of the hose until water comes out of it and, as long as you hold the open end lower than the water surface in Container A, the water will keep flowing up out of A into B.
But will this always work? Not necessarily.

Suppose that Container A is a cylinder, say, 3 metres in diameter (the diameter is not important here) and 12 metres in height. The water in it is 1 metre deep. You climb up the cylinder, lower your hose into the water, and drop the other end down to Container B, which you have ensured is lower than the surface of the water in A. In this situation, the top of the hose, our inverted-U, is 11 metres above the surface of the water in A.
You suck on the hose but can't get the water to rise up and out of Container A. Ahah, you cry! It's just the extra weight of water because the cylinder happens to be so high. So you get a powerful pump to get the siphon effect working and then all is well .. isn't it?

No. The water won't siphon - even if you use the most powerful pump on Earth! It's simply impossible.

Earth's atmosphere pushes down on the surface of the water in Container A with enough force to support a column of water approximately 10.3 metres high inside your hose. But the vertical distance from the water surface to the top of the cylindrical container is 11 metres. Even if you create an absolute vacuum inside the hose, the water will never rise up to the top of Container A and flow over and down into Container B because Earth's atmosphere can't push down hard enough to support an 11 metre column of water.
10.3 metres. That's it for water. Trying to use the siphon effect to transport water into space just can't work.

Incidentally, if you have an inverted-U tube with both open ends at or near sea-level and the top of the inverted-U above the vast majority of the atmosphere, at a height of 500 km, the air pressure inside the top of the tube will be equal to that of the atmosphere outside the tube, i.e. a very good vacuum. In fact, the air pressure inside the tube at any height you care to specify will always be equal to the air pressure outside the tube at that same height.

Does that help to clarify the situation?

ERRORIST · 2004-11-23 07:02:00

OK, what if one open end was 10 feet above the other open end and both ends are at or near sea level? Both ends would be within the 10m distance where a siphon does work.

Shaun Barrett · 2004-11-23 07:41:26

O.K., I'm listening.
You've got the two open ends close to sea-level, one end 10 feet higher than the other.

Now, how high is the bend?
What, exactly, are you trying to achieve?

ERRORIST · 2004-11-23 08:04:27

Say the tube is primed all the way up into space and both ends are in water near sea level. The elevation of one end of the tube is ten feet higher than the other end that is also in water. Will the water flow to the lower elevation?

GCNRevenger · 2004-11-23 08:56:50

NO Errorist, you are not getting it:

The height of the BEND is limited to ~10m, not the hight difference!

36,000,000m to GEO is quite a bit more then 10m.

Shaun Barrett · 2004-11-23 19:27:48

Well, GCNR, I understand where you're coming from here but, in my experience, getting annoyed with someone over a theoretical point rarely helps to get the point across.

ERRORIST, let's forget about running tubes up the space elevator to geosynchronous orbit for a moment. There's something fundamental about liquids in tubes I think you are not aware of.

Let's imagine something very straightforward and basic: I have a clear plastic tube 20 metres long. I place the tube in my swimming pool and jiggle it around to get all the air bubbles out, ensuring the whole tube is completely filled with water. O.K.? The tube is fully immersed in my pool and it's full of water.

Now, I reach in and place an airtight watertight bung in one end of the tube, ensuring the tube remains submerged and full of water at all times.
Next, I lift the sealed end of the tube out of the pool, again ensuring the open end stays beneath the surface and the tube remains filled with water.
I then proceed to raise the sealed end of the tube higher and higher, by means of climbing a handy 15 metre step-ladder standing next to the pool. (Doncha just love these thought experiments?! :;): )

Once the sealed end of the tube gets to a height of 10.3 metres above the surface of the pool water, something interesting happens. Even though we lift the sealed end higher still, the level of water inside the tube remains at 10.3 metres above the level of the pool water.
As we move up the ladder, raising the sealed end of the tube to 15.3 metres above the water in the pool, we notice the water level inside the tube is now 5 metres below the bung.

So, what's in the tube above the water? Effectively a vacuum. (I say "effectively" because it's not a 'hard vacuum'; there will be a tiny amount of water vapour present but, if you could get inside the tube, you'd need a pressure suit to survive.)
So, why doesn't the vacuum suck the water up into the top 5 metres of the tube? The answer is that a vacuum doesn't actually 'suck' anything. Things like gases and fluids have to be pushed into a vacuum by the higher pressure in their vicinity.
Holding up a column of water against the influence of gravity, inside a plastic tube, takes pressure. The pressure, in our example above, is supplied by the weight of Earth's atmosphere pushing down on the surface of the pool water. But that weight is completely balanced by the weight of just 10.3 metres of water inside the tube. The atmosphere can't push down hard enough to support a column of water any higher than this.

Any clearer?

patrick · 2004-11-27 09:10:49

I understand. But, In order for the vacuum to occur the water has to leave the tube. So if you place one tube end ten feet above the other and both ends are imersed in the water then the water should flow from one open end to the other open end instead of just emptying out both ends at the same time. It should flow from the higher elevated tube end to the lower one.

Austin Stanley · 2004-11-27 23:24:06

No you don't understand.

I think Shaun had the right way of explaining it. Vacume doesn't "suck" anything. What happens is the rest of the atmosphere pushes back.

Think of this, ever put your finger on top of a straw and pull liquid out of a cup that way? Gravity should pull the liquid out of the straw and onto the floor, but it doesn't because the rest of the atmosphere has enough force (pressure) to keep (some) of it inside the straw.

The problem is comparitivly the force of our atmosphere is small and the force of gravity is very large. There is only enough force (pressure) in our atmospehre to push up ~10 meters of water agains't earth's gravity. That is all the force there is. If the diffrence in the two sides of these tubes is greater than this 10 meters, there is no possible way the water can siphon from one side to the other.

It's like a car trying to climb a hill to cost down the side. Sure, there may be potentialy greater energy for the car if it can climb all the way over the top of the hill, but if the hill is to tall, the car cannot climb it, no matter how much energy it might get on the other side.

ERRORIST · 2004-11-28 19:34:21

If the diffrence in the two sides of these tubes is greater than this 10 meters, there is no possible way the water can siphon from one side to the other.

+36000Km -36000Km + 10 feet = +10feet
Thats the point 10 feet is less than the 30 Meters so a flow would occur from the higher end to the lower end no mater how high the two sides are.

Austin Stanley · 2004-11-28 19:46:33

No, no, no.

On either side of the tube, there is only enough force to push the water up 10 meters. 10 meters, that is it. The water level can never rise above 10 meters. That still leaves 35,999.990km to go. In order for a siphon to work, the water would have to be able to rise all that distance. It's not going to hapen.

Shaun Barrett · 2004-12-09 01:58:36

You still there, ERRORIST?
Has Austin's explanation helped you to see what we're driving at, or are you still convinced your 36,000 km siphon will work?
???

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#51 2004-11-22 18:32:05

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#52 2004-11-22 19:20:36

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#53 2004-11-22 21:46:10

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#54 2004-11-22 22:09:21

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#55 2004-11-22 22:39:17

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#56 2004-11-22 22:47:35

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#57 2004-11-22 22:49:45

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#58 2004-11-22 22:50:11

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#59 2004-11-22 22:52:55

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#60 2004-11-22 23:18:19

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#61 2004-11-22 23:29:02

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#62 2004-11-22 23:42:56

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#63 2004-11-22 23:44:54

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#64 2004-11-23 02:16:19

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#65 2004-11-23 07:02:00

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#66 2004-11-23 07:41:26

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#67 2004-11-23 08:04:27

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#68 2004-11-23 08:56:50

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#69 2004-11-23 19:27:48

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#70 2004-11-27 09:10:49

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#71 2004-11-27 23:24:06

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#72 2004-11-28 19:34:21

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#73 2004-11-28 19:46:33

Re: Carbon Nanotube Cable, or Elevator shaft ? - Eifel Tower to Geosynchronous

#74 2004-12-09 01:58:36

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