And it flexes down and then up every time the train passes, and when it flexes down there will be a possibility of lateral movement too, and that introduces a real problem, because water will leak in at almost every joint no matter what you do, the pressure differential is just too big to reasonably prevent it.
Trans Atlantic Tunnel?
- Thread starter Ironstark
- Start date
Maybe a better way to look at it is what sort of scenario would make a tunnel economical? The only obvious one is a situation where oil and gas are extremely rare rather than plentiful, thus making air travel a curiosity rather than something for the masses. It will also slow down shipping substantially.
Throw in a situation where the Atlantic suddenly becomes dodgy for shipping (extended cold war threatening the shipping lanes - say with an empire based on France on one side, and a united US and UK on the other) and it is possible that you might find a country willing to put the money in.
Realistically I think you're looking at a bored tunnel rather than this submerged anchored tube idea though, and it will be on conventional rails as well. Somewhere near 200mph should be possible, giving a travel time of ~24 hours from London to New York. Coal fired liners managed about 5 days at best, usually making for a very uncomfortable crossing - and cargo ships will be two weeks.
Throw in a situation where the Atlantic suddenly becomes dodgy for shipping (extended cold war threatening the shipping lanes - say with an empire based on France on one side, and a united US and UK on the other) and it is possible that you might find a country willing to put the money in.
Realistically I think you're looking at a bored tunnel rather than this submerged anchored tube idea though, and it will be on conventional rails as well. Somewhere near 200mph should be possible, giving a travel time of ~24 hours from London to New York. Coal fired liners managed about 5 days at best, usually making for a very uncomfortable crossing - and cargo ships will be two weeks.
So it leaks a wee bit. The pressure differential is FAR worse in mountain tunnels, and they do OK. There will clearly need to be continuous pumping to keep up the lowgrade vacuum, but that's not too awful. You're also going to have to deal with the salt that leaks in, too, which is a little less trivial.
Erm, rock is slightly more viscous than seawater. And given the erosive power of a ultrahigh-pressure jet of salt water, I don't think that a little leak would remain little for very long.
For such a scenario to make the tunnel more economical rather than more unrealistic would mean a world that has successfully negotiated the transition from fossil fuels to alternative energy sources. It raises the question why fossil fuels like oil and gas are scarce in the first place.
Ever read an account of tunnel boring? Water leakage is very, very common, sometimes you even get mud in the middle of a mountain that's a total pain to deal with.
The difference, good sir, is that seawater CONTAINS LARGE AMOUNTS OF DISSOLVED SALT. Saltwater is rather more corrosive than freshwater.
That's like saying the Titanic "had a bit of an accident".
I think maybe you're misunderstanding the difference between pressure and gravity. In any case, a mountain tunnel doesn't flex, and rock isn't noted for its liquidity.
Well sure, if you can afford to constant pump out a tunnel 5000 km long and 6 metres in diameter.
Now imagine you're surrounded by nothing but water, pressing in at 6+ atmospheres, and you can't seal the damned tunnel because it keeps flexing.
No anchorage needed in case of submerged floating tunnel, because the buoyancy can be regulated.
It will be like giant hose -- 6m ( external ) width and 6 000 000m long.
Flexing is immaterial with such scale of width to lenght ratio.
Check out for Pat Gunkle's "topopolis" -- he envisions ROTATING tube of hundreds or thousands of km wide ( with bio"sphere" printed on the inner side and 1G centrifugal gravity ) which is woven around a star.
With 1 : 1 000 000 width to lenght ratio, the only flexing limit would be no sharper than 1.5 gees turns.
I see the transcontinental hose as consisting of smart tubular modules. Mass produced they'd cost very little per mile.
It will be like giant hose -- 6m ( external ) width and 6 000 000m long.
Flexing is immaterial with such scale of width to lenght ratio.
Check out for Pat Gunkle's "topopolis" -- he envisions ROTATING tube of hundreds or thousands of km wide ( with bio"sphere" printed on the inner side and 1G centrifugal gravity ) which is woven around a star.
With 1 : 1 000 000 width to lenght ratio, the only flexing limit would be no sharper than 1.5 gees turns.
I see the transcontinental hose as consisting of smart tubular modules. Mass produced they'd cost very little per mile.
Currents make anchorage a requirement.
Hoses don't do well if you try to make them out of concrete
No it isn't, because you have to build it in sections. Also, concrete doesn't flex well.
You can't build it in one piece, each section will be probably no more than a few hundred metres, and quite a number of sections will have to include extendible sections to take account of continental drift.
Except that you will need a massive volume of materials. Assuming you make it 6m wide inside (two way), and your walls are half-a metre thick your cross sectional areas is 40.84 square metres, which means you require over 40,000 cubic metres of material per km.
Currents energy could be utilized.
6 x 6 000 000 m concrete object ( modular! ) is like made of bubblegum. You can calculate easily how much twist and flex can this take alowing just 0.1 degrees deviation between the sections.
You CAN build in one piece. Pring the tube. The notion about the continental drift of several cm p.a. as opposed to entire %s of changes resulting from external forces is very stupid thing.
So what. Materials are cheap - indeed dirt cheap - carbon. Nobody says two-way. One way. One "track" which is the tube wall itself.
To be fair, the wavelength of the oscillations of the tunnel should be, by design, very long, as to not to be noticeable in each of the sections.
I mean, that's how it should be, precisely to avoid that problem. On the other hand, we probably don't have the technology yet to make those leaks a marginal problem. With out technology those leaks would be something that really breaks the project.
Something i wonder: what is the absolutely minimum depth this tunnel could be to avoid conflicting with merchant ships and atmospheric conditions? I'm thinking that whales could be dealt with through warning lights. The gulf current might not be much of a problem if the tube is parallel to its flow, in fact, could it be used to provide power to the structure?
Only with firm anchorages.
And give means it will leak, leaks build up, soon enough (maybe even before completion) the whole thing's shot because of just tiny leaks.
Pring? Can you explain that in English?
Even if you got the wall down to 10 cm thick, that's still over 7,500 cubic metres per km, or over 38,000,000 cubic metres for the whole length.
Two-way is a necessity.
Fine for currents, how do you work that for a train with a motor car weighing more than 27 tons?
I don't know about atmospheric conditions, but the Seawise Giant has a stated draught of 24.61 m, though I don't know if that's loaded or not. Best make it 30-40m to be safe.
The gulf current flows north on the US east coast and south on the Spanish west coast, so I don't think it's going to be a lot of help.
What if they had for whatever reason never existed - perhaps the geology of the world is subtly different so the tend not to be trapped underground in drillable form, but perhaps as oil shales? If we had never invented the internal combustion engine and built up an infrastructure based on it, I suspect shale oil would never have become economical.
Such a world would be based on coal and then nuclear/renewables. That makes air travel a curiosity rather than something for the masses, and makes shipping slower and more expensive (coal is much more difficult to handle - you're relying on stokers into maybe the 1960s).
Since it's a maglev and all cars are motor cars (true?), i'm thinking you could send the cars in such frequency that their vibracions interfere destructively with each other, resulting in a zero net vibration caused by the train.
Ugh... 30m is around 4 atm.... less than 6, but it's still quite a bit of pressure.
I can't find reliable maps, all of them show different routes, but most of them agree that the gulf stream splits into minor currents either in front of ireland or in front of NW Spain, or somewhere in between... and that's quite adequately on the way from NY to London.
Edit: found this
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You need to get below the storm wave base to avoid flexing, around 200 m deep for the most intense storms. At that depth, motion from waves is minimal, and motion from currents is constant and can be ignored, unless your structure ends up resonating.
I think the only reasonable depth consideration is to avoid being obstacle for ship traffic.
Currents, waves, buoyancy ... are something which the Archimedes ( submerged ) bridge can handle via adjusting its waving with the external forces, even utilizing them ...
Currents, waves, buoyancy ... are something which the Archimedes ( submerged ) bridge can handle via adjusting its waving with the external forces, even utilizing them ...
Other maps show the complicated pattern of currents in the Atlantic a lot more clearly. The site at http://oceancurrents.rsmas.miami.edu/atlantic/atlantic.html is particularly informative. It's not just the well known Gulf Stream out there, there is a complex network of oceanic currents and the ocean is dynamic. I am not sure anyone has even adequately modelled the forces that a subsurface Atlantic 6m wide tunnel would experience as the number of variable influences is high, so I am sceptical about any value cited here. A 5000 km tube is going to cut across dozens of currents so it's a complicated problem.
Come to think of it, where does the 6m width figure for the tunnel come from? The conceptual video seems to show a tunnel more like 50 m wide and if your tunnel is only 6 m wide you are going to have very little room for someone to stand up. Draw a circle to represent the tunnel, then draw a rectangle inside that to represent the carriage to get an idea of the dimensions required to fit that in. Then think how much space you would need for seats (4 or 6?) and a passageway, the running gear, the motive power for moving your train, the walls of the train, the walls of the tunnel, cables and vacuum lines in the tunnel etc. And I can see no way that you can fit this all into 6 metres unless you lie your passengers down like sardines and provide no escape or access routes. So, I question this figure of a 6m wide tunnel as it is unrealistic.
This might be a solvable engineering problem one day (the video suggests a date of 2099) but not yet. Maglev trains themselves have only been used in much simpler environments i.e. on stable land using a conventional track, with the safety net of being able to stop the train anywhere and to step off safely if there's a problem. As someone else noted, this tunnel would be a vacuum chamber millions of times bigger than any previously constructed, so that's more unproven technology on the required scale. As for suggestions of plasma windows, current energy etc, we are years if not decades away from anything close to a scaleable test of those ideas so it's just conjecture. By 2099 maybe, by 2012 no chance.
"Materials are cheap - indeed dirt cheap - carbon. Nobody says two-way. One way. One "track" which is the tube wall itself."
Carbon may be cheap but graphene isn't (if that's the construction material of choice?). Even the required volume of carbon nanotubes is far beyond anything we can manufacture (and it's the purification of nanotubes that makes them expensive, carbon is dirt cheap but pure CNTs aren't, at the moment that's still an unavoidable cost). The EE video linked at the start of this thread talks about billions of tonnes of steel, 100 years and a $US12trillion bill so I don't know where the idea of this being cheap comes from?
The conceptual video showed a two way track not a one-way one, so why are you saying it would only be one way?
If you do have only a one way system how exactly would you plan to rescue people, or send out maintenance crews, to a spot 2000 miles from the tunnel entrance? If you don't have a way of evacuating people from every single spot along the route you would never get approval to build this tunnel as it would be uninsurable, and a death trap.
Watching the video, at least the first part, the general idea seems to be for a track based train. So how does a trackless maglev train work since none has even been built before?
Returning to the problem of generating a vacuum again, what level of vacuum are we talking about here? I am not a vacuum expert like pdf27 but I have several years experience of working with them. Getting down below 1mm Hg of pressure is quite easy, a simple rotary pump does the job cheaply and efficiently. But going down to the ultravacuum level, which is what I assume some people are talking about, is much more difficult. At such low pressures you essentially require gas molecules to randomly move out of the chamber and that is a statistical exercise i.e. it takes time and there's not much you can do to speed the process up. A colleague of mine has a high vacuum chamber of about a cubic meter in volume that takes 6+ hours to evacuate when all is working well. How you can scale this up to the dimensions of the proposed tunnel is beyond me, unless you plan to have something like a dozen large diffusion pumps EVERY 100 metres running round the clock. There is no way you can evacuate air from the middle of the tunnel using pumps only at the ends because once you get below a few mmHg of pressure it would take too long to remove the remaining gas molecules (weeks, months??). The logistical and maintenance problems alone don't bare thinking about, let alone the costs.
And if you've ever built a vacuum rig then you quickly appreciate how difficult it is to maintain a vacuum. A single scratch in a flange, a small speck of dust on an O-ring seal and air leaks in. Then you have to strip it down, clean it and start again. And that's in a clean lab on a stable bench, let alone in the middle of the ocean. I may also be missing something here but how do you get your maglev train from the train track in the open air into your airtight tunnel without losing the vacuum? What keeps the air out of the tunnel mouth?
So, do you really need a vacuum-filled tunnel because I don't see how it can work?
Come to think of it, where does the 6m width figure for the tunnel come from? The conceptual video seems to show a tunnel more like 50 m wide and if your tunnel is only 6 m wide you are going to have very little room for someone to stand up. Draw a circle to represent the tunnel, then draw a rectangle inside that to represent the carriage to get an idea of the dimensions required to fit that in. Then think how much space you would need for seats (4 or 6?) and a passageway, the running gear, the motive power for moving your train, the walls of the train, the walls of the tunnel, cables and vacuum lines in the tunnel etc. And I can see no way that you can fit this all into 6 metres unless you lie your passengers down like sardines and provide no escape or access routes. So, I question this figure of a 6m wide tunnel as it is unrealistic.
This might be a solvable engineering problem one day (the video suggests a date of 2099) but not yet. Maglev trains themselves have only been used in much simpler environments i.e. on stable land using a conventional track, with the safety net of being able to stop the train anywhere and to step off safely if there's a problem. As someone else noted, this tunnel would be a vacuum chamber millions of times bigger than any previously constructed, so that's more unproven technology on the required scale. As for suggestions of plasma windows, current energy etc, we are years if not decades away from anything close to a scaleable test of those ideas so it's just conjecture. By 2099 maybe, by 2012 no chance.
"Materials are cheap - indeed dirt cheap - carbon. Nobody says two-way. One way. One "track" which is the tube wall itself."
Carbon may be cheap but graphene isn't (if that's the construction material of choice?). Even the required volume of carbon nanotubes is far beyond anything we can manufacture (and it's the purification of nanotubes that makes them expensive, carbon is dirt cheap but pure CNTs aren't, at the moment that's still an unavoidable cost). The EE video linked at the start of this thread talks about billions of tonnes of steel, 100 years and a $US12trillion bill so I don't know where the idea of this being cheap comes from?
The conceptual video showed a two way track not a one-way one, so why are you saying it would only be one way?
If you do have only a one way system how exactly would you plan to rescue people, or send out maintenance crews, to a spot 2000 miles from the tunnel entrance? If you don't have a way of evacuating people from every single spot along the route you would never get approval to build this tunnel as it would be uninsurable, and a death trap.
Watching the video, at least the first part, the general idea seems to be for a track based train. So how does a trackless maglev train work since none has even been built before?
Returning to the problem of generating a vacuum again, what level of vacuum are we talking about here? I am not a vacuum expert like pdf27 but I have several years experience of working with them. Getting down below 1mm Hg of pressure is quite easy, a simple rotary pump does the job cheaply and efficiently. But going down to the ultravacuum level, which is what I assume some people are talking about, is much more difficult. At such low pressures you essentially require gas molecules to randomly move out of the chamber and that is a statistical exercise i.e. it takes time and there's not much you can do to speed the process up. A colleague of mine has a high vacuum chamber of about a cubic meter in volume that takes 6+ hours to evacuate when all is working well. How you can scale this up to the dimensions of the proposed tunnel is beyond me, unless you plan to have something like a dozen large diffusion pumps EVERY 100 metres running round the clock. There is no way you can evacuate air from the middle of the tunnel using pumps only at the ends because once you get below a few mmHg of pressure it would take too long to remove the remaining gas molecules (weeks, months??). The logistical and maintenance problems alone don't bare thinking about, let alone the costs.
And if you've ever built a vacuum rig then you quickly appreciate how difficult it is to maintain a vacuum. A single scratch in a flange, a small speck of dust on an O-ring seal and air leaks in. Then you have to strip it down, clean it and start again. And that's in a clean lab on a stable bench, let alone in the middle of the ocean. I may also be missing something here but how do you get your maglev train from the train track in the open air into your airtight tunnel without losing the vacuum? What keeps the air out of the tunnel mouth?
So, do you really need a vacuum-filled tunnel because I don't see how it can work?
"You need to get below the storm wave base to avoid flexing, around 200 m deep for the most intense storms. At that depth, motion from waves is minimal, and motion from currents is constant and can be ignored, unless your structure ends up resonating."
Quite possibly, I'm happy to take your word for it. The problems of pressure and leaks obviously increase though at the lower depth.
Quite possibly, I'm happy to take your word for it. The problems of pressure and leaks obviously increase though at the lower depth.