Space Elevators and Pipelines

GCNRevenger · 2004-11-30 20:27:20

I don't think there is a known one on the Moon Errorist, not of any size anyway.

ERRORIST · 2004-11-30 20:34:56

No, I mean can we get to Mathilde and mine the C on it?
Then ship it to our moon?

GCNRevenger · 2004-11-30 20:55:23

Oh, well asteroid mining is a whole different matter. The short answer is "not right now"

ERRORIST · 2004-11-30 21:14:49

http://www.ibiblio.org/lunar/school/sol … ecarb.html

Looks like a high percentage to me. Why not capture one and place it in orbit around the moon or just let it slam into it?

GCNRevenger · 2004-11-30 21:32:23

And how do you do that?

Plus, if you miss, the Earth could be hit

ERRORIST · 2004-11-30 21:42:11

Don't miss

GCNRevenger · 2004-11-30 22:17:12

Easy for you to say...

"Whoops, the engine burn was too short and the turbopump bearings are cracked, now the rock is going to fall on eastern China"

ERRORIST · 2004-12-01 04:50:26

Have back up systems.

GCNRevenger · 2004-12-01 07:53:57

There is a real risk that all propulsion systems would fail or you make a mistake in trajectory allignment or somthing. The question is, how much risk is too much when you are talking about accidently obliterating thousands of square kilometers of the Earth... so you can save a buck on launch costs

John Creighton · 2004-12-01 09:25:25

Okay time to propose something a little crazy. If you pump gas up a pipeline you must lift all the gas above you. This greatly reduces the possible acceleration of the fluid in the pump because the pressure distance over the length of the pump is reduced . Work is the proportion to the integral of the change in pressure over the distance.

If there was zero pressure in front of the gas you were accelerating the work the pump would do on that gas would be much greater. So the pump first compress the gas to a suitable pressure then accelerates it over an evacuated tube so that when the gas is near the end of the tube the maximum pressure of the shock wave is 90 bars. This 90 bar sock wave will carry waves of compressed gas up the tube at the speed of sound in the tube or greater.

Although the stress due to the acoustic vibrations on the tube could be worse then a static 90 bar pressure and may induce more state or chemical transformations on the surface of the tube the shock wave will carry momentum as well as potential energy. If the 90 bar shock wave was half the temperature of the gas in the tube then if the wave fully dissipates the resulting pressure would be around 90 bars of static pressure. Thus with such an arrangement the pressure in the tube could first increase as you go up the tube before it decreases.

One way to create the shock wave would be to put to surfaces in contact with each others like boards. Forces induced by Pizzo electric crystals could be used to bend the two surfaces apart. Allow gas to slide in and then the two ends could be closed well keeping a compressed bulge of gas just before the end of the tube. The crystal then accelerates the bulge of gas between the two boards by propagating the envelop across the board and then releasing it the bulge of gas into the tube. Several such envelops could be sustained simultaneously in the board to continuously launch a series of compressed gases sock waves into the tube at super sonic speed. These shock waves will prorogates up the tube both by their own momentum and by acoustic motion that will travel at the speed of sound in the medium faster then the mean velocity of the gas. This sounds allot like the nanotech pizzo electric drive where gas was launched out the wedge of a diamond due to acoustic vibrations.

This isn’t completely necessary for the pipeline to work but if it does work it could increase the flow rate of the gas and reduce the number of pumps. Both of these properties are very desirable for the space pipeline.

GCNRevenger · 2004-12-01 09:33:21

Thats a silly idea, I don't think you can get the gas shock wave to propogate through the whole length of the pipeline before disorderd motion takes over. High frequency sound is also known to destroy polymers that the pipeline will be made from.

Plus, this will really kill your flow rate.

John Creighton · 2004-12-01 09:37:47

High frequency sound is also known to destroy polymers that the pipeline will be made from.

You could try spacing the pulses future apart. That would lower the frequency but you still would have to worry about the harmonics. But then you have a choice of sine wave shock waves, square wave shock waves or spaced sine wave shock waves.

Plus, this will really kill your flow rate.

I suppose that depends on how cool you can keep the shock waves. The lower the temperature the greater the density that they will carry. If you make it too cool you might have to worry about phase transitions of the gas or an increased brittleness of the pipeline. Besides if time permits I would like to explore all possible design methods to see if any of them be it a climber or a pipeline may reach that magic flow rate of 10% of the mass of the elevator or more per year. My guess is a magnetic train would be the fastest but such an elevator would cost way too much to build. I think the best hope is construction using space resources and Nuclear thermal may just be efficient enough to get the resources to GEO.

ftlwright · 2004-12-01 23:20:55

Won't work. The pipeline idea is based upon the premise that you can completely isolate the gas/fluid on the inside from the pipes external environment, i.e. a perfectly rigid volume. This is impossible. Keep in mind that must of the strength in carbon-carbon chains are coupled between their stress-strain directions. If you take away their flexibility, they won't be strong enough to endure the induced tension. There are many other reasons you need these things to be flexible.

John Creighton · 2004-12-02 09:19:35

Won't work. The pipeline idea is based upon the premise that you can completely isolate the gas/fluid on the inside from the pipes external environment, i.e. a perfectly rigid volume. This is impossible. Keep in mind that must of the strength in carbon-carbon chains are coupled between their stress-strain directions. If you take away their flexibility, they won't be strong enough to endure the induced tension. There are many other reasons you need these things to be flexible.

Interesting comment. I presume you are referring to the shock wave method of fuel transportation as opposed to a constant flow. The shape of the shockwaves will effect the strain on the walls of the tube. How much the tubs are strained will depend on how think the layer of nano tubes is that wraps around the pipe. If the changes in strain are to great this should increase the turbulent effects because the pipe will be contently narrowing ahead of the peak of the shock wave. The turbulence will be due to the sides of the wave being stripped off faster then the viscous effects can sustain. The rate the tube narrows ahead of the shock wave can be changed by changing the shape of the shockwave and increasing the thickness of the pipe. I am unclear whether this would dissipate the shockwave too quickly to have any advantages over a normal constant flow in the pipe. I wonder how much control you could have over the shock wave in terms of its pressure and temperature distribution and what shape would be optimal.

GraemeSkinner · 2004-12-06 04:14:29

If you leave aside the physics for a while of the pipeline, and compare the two ideas side by side, you'd have to opt for the elevator. A pipeline would be designed to pump one type of gas, thats it, its a one off deal; an elevator can be used for so much more than one item - a single elevator load could be used for carrying materials for orbital construction, bottled gas, food, etc. When you've got the option of multiple loads of the elevator why would you restrict yourself to the pipeline idea?

Graeme

John Creighton · 2004-12-06 10:59:51

If you leave aside the physics for a while of the pipeline, and compare the two ideas side by side, you'd have to opt for the elevator. A pipeline would be designed to pump one type of gas, thats it, its a one off deal; an elevator can be used for so much more than one item - a single elevator load could be used for carrying materials for orbital construction, bottled gas, food, etc. When you've got the option of multiple loads of the elevator why would you restrict yourself to the pipeline idea?
Graeme

If it is possible to move fluid up a pipe faster then it is up a wire then the fluid can be used to make more space elevators or pipelines. If you move methane up the pipeline you can use methane as rocket fuel so you don’t have to worry about boil off and can take your time fuelling up or you can use hydrogen to get better ISP. If you use hydrogen you have the carbon left over to build more space elevators. If the pipeline can move methane up the pipeline at a rate equal to 10% of the pipeline mass or more per year then growth in launch capacity due to pipelines will grow greater then or equal to the interest rate. The net result will be that launch costs will fall exponentially until the cost to GEO is near the marginal operating cost of the elevator.

GraemeSkinner · 2004-12-07 00:27:43

But for that to happen you'd have to get Methane (or whatever) to go up a pipeline at a reasonable rate which is not going to happen. An elevator could carry fuel cells/bottles/whatever ready to fix straight onto orbiting crafts without need for pumping chemicals anywhere - simply take the empty container off and put the full one on.

Graeme

ERRORIST · 2004-12-07 00:59:08

A particle beam shooting up the pipeline could do it.

GraemeSkinner · 2004-12-07 01:05:42

How???

ERRORIST · 2004-12-07 01:13:19

In the beam the particles reach escape velocity and are confined within the tube.

GraemeSkinner · 2004-12-07 01:21:00

This has been discussed many times before, I don't believe the physics and facts meet with this idea in any way, it is in other words a pipe dream

I've read the many other pipeline threads and unless there are new arguments for how they'll work I don't think I'll be changing my opinion of them.

Graeme

ERRORIST · 2004-12-07 01:24:21

Not a pipe dream at all. The particles can be forced to never impact the wall of the tube, also.

GraemeSkinner · 2004-12-07 01:36:01

Not a pipe dream at all. The particles can be forced to never impact the wall of the tube, also.

If that is your opinion, I'm not going to try and change it, others have tried and failed in the past.

Until someone can prove the physics, and I mean physics not just some vague idea how it will work I'll not be changing my opinion of pipelines.

Graeme

John Creighton · 2004-12-07 09:10:20

But for that to happen you'd have to get Methane (or whatever) to go up a pipeline at a reasonable rate which is not going to happen. An elevator could carry fuel cells/bottles/whatever ready to fix straight onto orbiting crafts without need for pumping chemicals anywhere - simply take the empty container off and put the full one on.
Graeme

For any elevator to be economical it has to have a reasonable delivery rate in terms of mass per orbit per mass of elevator. I would like to explore several concepts and see if any of them can meet that magic mass flow number per year equal to 10% the mass of the elevator. It could be a pipeline, a climber, a magnetic train or what ever.

This has been discussed many times before, I don't believe the physics and facts meet with this idea in any way, it is in other words a pipe dream
I've read the many other pipeline threads and unless there are new arguments for how they'll work I don't think I'll be changing my opinion of them.

I understand skepticism. Until someone works out the physics skepticism is a very reasonable position to take. I will point out that with a flow rate of zero 90 bars of hydrogen at the base will mean you will have 0.37 bars of hydrogen at an altitude above 3000 m. At 6000 m gravity drops by ¼. Thus with one really strong pump at the base you can get hydrogen along way up the pipeline. Now this is with a zero flow rate. Clearly the pressure drop will be quicker with a higher flow rate. Clearly methane will not make it as far up the pipe with 90 bars of pressure. I have suggested propagating shockwaves up the pipe to try an increase the distance one pump will elevate the gas. If this doesn’t work the only solution is more pumps. More pumps will increase the mass but decrease the flow rate. Weather or not there is a break even point in terms of flow rate per mass I don’t know. Hopefully some day soon I will work out the physics. But I am doing masters in (control systems)/(electrical engineering) not computational fluid mechanics. If I want to finish at a reasonable time I can’t spend too much time on these side curiosities.

ERRORIST · 2004-12-07 10:59:34

I will work out the physics. But I am doing masters in (control systems)/(electrical engineering) not computational fluid mechanics. If I want to finish at a reasonable time I can’t spend too much time on these side curiosities.

To me it is a hobby like collecting coins.

New Mars Forums

Announcement

#101 2004-11-30 20:27:20

Re: Space Elevators and Pipelines

#102 2004-11-30 20:34:56

Re: Space Elevators and Pipelines

#103 2004-11-30 20:55:23

Re: Space Elevators and Pipelines

#104 2004-11-30 21:14:49

Re: Space Elevators and Pipelines

#105 2004-11-30 21:32:23

Re: Space Elevators and Pipelines

#106 2004-11-30 21:42:11

Re: Space Elevators and Pipelines

#107 2004-11-30 22:17:12

Re: Space Elevators and Pipelines

#108 2004-12-01 04:50:26

Re: Space Elevators and Pipelines

#109 2004-12-01 07:53:57

Re: Space Elevators and Pipelines

#110 2004-12-01 09:25:25

Re: Space Elevators and Pipelines

#111 2004-12-01 09:33:21

Re: Space Elevators and Pipelines

#112 2004-12-01 09:37:47

Re: Space Elevators and Pipelines

#113 2004-12-01 23:20:55

Re: Space Elevators and Pipelines

#114 2004-12-02 09:19:35

Re: Space Elevators and Pipelines

#115 2004-12-06 04:14:29

Re: Space Elevators and Pipelines

#116 2004-12-06 10:59:51

Re: Space Elevators and Pipelines

#117 2004-12-07 00:27:43

Re: Space Elevators and Pipelines

#118 2004-12-07 00:59:08

Re: Space Elevators and Pipelines

#119 2004-12-07 01:05:42

Re: Space Elevators and Pipelines

#120 2004-12-07 01:13:19

Re: Space Elevators and Pipelines

#121 2004-12-07 01:21:00

Re: Space Elevators and Pipelines

#122 2004-12-07 01:24:21

Re: Space Elevators and Pipelines

#123 2004-12-07 01:36:01

Re: Space Elevators and Pipelines

#124 2004-12-07 09:10:20

Re: Space Elevators and Pipelines

#125 2004-12-07 10:59:34

Re: Space Elevators and Pipelines

Board footer