Transatlantic Tunnel - Possible?

[RichmondCommu]

What's the fastest a submarine can go? Is there any limit to travel speed?? Won't be much of a view admittedly, even if they had windows. So any regular on the Manchester-London route will feel at home. Submerged under water on the outside, and can't see it from the inside

From memory around 30 to 35 knots and that would be one of the nuclear hunter-killers. Something similar to the Trident boats would be slower than that.

 

[najaB]

From memory around 30 to 35 knots and that would be one of the nuclear hunter-killers. Something similar to the Trident boats would be slower than that.

I'm pretty sure one of the Soviet-era killer subs could do in excess of 40 knots. Had the habit of making the crew glow in the dark though*.

*(Not to be taken literally)

 

[Xenophon PCDGS]

Had the habit of making the crew glow in the dark though.

Giving my age away, was this also not a side-effect on schoolchildren featured in the original "Ready Brek" TV adverts..

 

[krus_aragon]

Giving my age away, was this also not a side-effect on schoolchildren featured in the original "Ready Brek" TV adverts..

Nah, that's the uranium toothpaste from the previous advertisment. :P

 

[HSTEd]

Why would you need a five/six thousand kilometre tunnel to reach North America?

Surely you are not proposing a straight shot for New York?
AS the tunnel is likely to be far more expensive than a normal route on the surface surely you would cross the ~3000km to Labrador?

I wonder what a straight shot under the Arctic to the Canadian shield would come out at....

 

[NotATrainspott]

Why would you need a five/six thousand kilometre tunnel to reach North America?

Surely you are not proposing a straight shot for New York?
AS the tunnel is likely to be far more expensive than a normal route on the surface surely you would cross the ~3000km to Labrador?

I wonder what a straight shot under the Arctic to the Canadian shield would come out at....

If you're using a floating submerged tube, then there's not going to be much of a benefit to running via the land. Every tube section would be exactly the same as the previous one, constructed in the same way, regardless of the underwater geography. As the tube would be almost neutrally buoyant, the amount of anchoring needed would be small. As it would contain a vacuum, the tube would have a natural inclination to float so it can be held in place in tension using cables anchored wherever is convenient. On land, a tube would need to be above the ground, and as it wouldn't float it would need to be fully supported in compression by many more pillars. Underwater construction logistics are easier as heavy stuff can just float to where it needs to go, whereas on land you would need access roads or expensive helicopters. No one would ever see the tube underwater, so you can completely disregard visual impact, which can't be said for land. The underwater environment doesn't vary anywhere near as much as anywhere else on land either.

 

[HSTEd]

If you're using a floating submerged tube, then there's not going to be much of a benefit to running via the land. Every tube section would be exactly the same as the previous one, constructed in the same way, regardless of the underwater geography. As the tube would be almost neutrally buoyant, the amount of anchoring needed would be small. As it would contain a vacuum, the tube would have a natural inclination to float so it can be held in place in tension using cables anchored wherever is convenient. On land, a tube would need to be above the ground, and as it wouldn't float it would need to be fully supported in compression by many more pillars. Underwater construction logistics are easier as heavy stuff can just float to where it needs to go, whereas on land you would need access roads or expensive helicopters. No one would ever see the tube underwater, so you can completely disregard visual impact, which can't be said for land. The underwater environment doesn't vary anywhere near as much as anywhere else on land either.

Running on land is far less likely to result in any minor mishap leading to everyone dying horribly from decompression however - as repressurisation of the tube can occur in seconds rather than the length of time required to repressurise a many thousands of kilometre long tube from the ends.

And why would a tube have to be above ground? It can easily be buried in the surface.
And I was also thinking of a somewhat nearer tech tunnel where the vehicles are only moving a few hundred km/h in an atmospheric pressure tube. (Which would still float, as the mass of the gas in the tube is negligible compared to the mass of the tube)

 

[ainsworth74]

I'm pretty sure one of the Soviet-era killer subs could do in excess of 40 knots. Had the habit of making the crew glow in the dark though*.

*(Not to be taken literally)

No it shouldn't

There are two Soviet attack submarines (SSNs) that could do 40+ knots the Alfa and Papa class of boats. The Alfa's were the fastest class of SSN to actually enter serial production with a top speed of 41 knots. Whilst the Papa class of one prototype only is the fastest SSN ever produced with a top speed of 44 knots.

The Alfa's didn't have a single serious radiation accident but the lead boat did suffer a coolant failure which resulted in the liquid metal(!) coolant solidifying. They ended up scrapping her as it would be too expensive to fix. One of the reactors on the Papa class submarine was damaged during a maintenance period but I don't think that resulted in a release of radiation.

 

[HSTEd]

The Alfa's didn't have a single serious radiation accident but the lead boat did suffer a coolant failure which resulted in the liquid metal(!) coolant solidifying. They ended up scrapping her as it would be too expensive to fix.

AIUI this fault eventually claimed all the Alfas because the steam heating systems that were fitted on the dockside to ensure that the coolant remained liquid while the reactor was shut down kept failing - which resulted in the reactors having to be kept running at very low power at all times.

This caused major maintenance and reliability issues - and once one failed that was it - end of game for that boat.

 

[backontrack]

Where's that like button!

Agreed.

 

[ainsworth74]

AIUI this fault eventually claimed all the Alfas because the steam heating systems that were fitted on the dockside to ensure that the coolant remained liquid while the reactor was shut down kept failing - which resulted in the reactors having to be kept running at very low power at all times.

This caused major maintenance and reliability issues - and once one failed that was it - end of game for that boat.

I'm not sure that that fault was the reason for their withdrawal but certainly the expense and complexity of keeping them going was why they all went almost as soon a the Wall came down! An interesting design using liquid metal coolant but definitely not very practical.

 

[najaB]

... which resulted in the reactors having to be kept running at very low power at all times.

Pretty sure it also resulted in an overall higher radiation dose for the crew as well as the reactors were lightly shielded in comparison to other classes of vessel.

 

[ainsworth74]

Pretty sure it also resulted in an overall higher radiation dose for the crew as well as the reactors were lightly shielded in comparison to other classes of vessel.

Possibly but I've never come across anything that suggested that Alfa crews suffered any negative effects of their time serving aboard.

 

[RichmondCommu]

Thanks to the three of you for some very interesting information on Soviet SSB's. From what I've read the Soviet's had the technology but ran out of money to maintain it.

 

[NotATrainspott]

Running on land is far less likely to result in any minor mishap leading to everyone dying horribly from decompression however - as repressurisation of the tube can occur in seconds rather than the length of time required to repressurise a many thousands of kilometre long tube from the ends.

And why would a tube have to be above ground? It can easily be buried in the surface.
And I was also thinking of a somewhat nearer tech tunnel where the vehicles are only moving a few hundred km/h in an atmospheric pressure tube. (Which would still float, as the mass of the gas in the tube is negligible compared to the mass of the tube)

You could build the tube underground, but then you have to bore it out. That's going to be extraordinarily expensive and make it too expensive to build. If you have a submerged tube tunnel, then you just need to build each tube segment and float it out into position. Your tunnelling speed is the speed at which you can churn out tube segments from your factories. Building tube segments, floating them out into position and joining them together is something that would be easy to automate and so make cheap and easy.

 

[HSTEd]

You could build the tube underground, but then you have to bore it out. That's going to be extraordinarily expensive and make it too expensive to build. If you have a submerged tube tunnel, then you just need to build each tube segment and float it out into position. Your tunnelling speed is the speed at which you can churn out tube segments from your factories.

Building tube segments, floating them out into position and joining them together is something that would be easy to automate and so make cheap and easy.

You might be able to make it easy if you were building in sheltered waters - but I can assure you that doing so in the mid Atlantic in midwinter is an entirely different matter.

Your work boats will struggle to keep position and everything above water will be hit repeatedly by enormous waves.
Most proposals only assume work for half the year and going rather slowly at that.

And who said anything about boring out a tunnel? Just get the JCBs on the case - cut and cover tunnels in the middle of nowhere aren't very expensive, especially if you are willing to accept that the ground over the box is sufficiently shallow that all it will be able to support is turf.
And if you are running a saner, slower train in atmo at roughly 400-500km/h then you don't need a tube on land at all.

Just look at the specs for this so called "vac-train" - you can't have passengers pulling significant gs. It would never fly.

 

[BestWestern]

You could build the tube underground, but then you have to bore it out. That's going to be extraordinarily expensive and make it too expensive to build. If you have a submerged tube tunnel, then you just need to build each tube segment and float it out into position. Your tunnelling speed is the speed at which you can churn out tube segments from your factories. Building tube segments, floating them out into position and joining them together is something that would be easy to automate and so make cheap and easy.

However; how would the maintenance costs compare? A submerged tunnel one would assume is pretty much standard in terms of the basic structural requirements - admittedly the internals of it would be quite something to stand up to maglevs doing 000's of mph. But a submerged tube at deep sea depth would be under a hell of a strain from the pressures, surely? You'd need a phenomenal degree of maintenance to convince me to go down there anyhow!

 

[najaB]

Possibly but I've never come across anything that suggested that Alfa crews suffered any negative effects of their time serving aboard.

As I understand things, the light shielding meant that the reactor was supposed to be automated since it was dangerous to work around for any extended periods. But the automation wasn't quite up to the task so people had to work in the compartment more often than was sensible. They probably avoided serious health consequences by rotating the reactor crews more often than they did with more traditional designs.

 

[Xenophon PCDGS]

What would the highest water pressure exerted on the tube be at the deepest depth envisaged?

 

[HSTEd]

What would the highest water pressure exerted on the tube be at the deepest depth envisaged?

The proposals would be for an Archimedes Bridge.
The tube would be submerged at a depth of 50-100m [so 5-10 atmospheres] and would be constantly attempting to float to surface but would be held in place by tethers attached to the seabed using some form of vacuum anchor.

So not particularly deep.

 

[themiller]

I don't know who could write a safety case to cover the operation of the tube or tunnel (once built). Just think of rescue arrangements in the Channel Tunnel then think of a tunnel thousands of miles long.....
If built and a safety case were to be achieved, any train running through a snaking, stayed, floating tube would cause the tube to flex so speed would not be likely to be very high. Now, who's going to maintain the outside of the tunnel and inspect the stay cables in situ?
Power transmission along the tube/tunnel would require many sub-stations to be spaced along the route.
To bring in another aspect, the Atlantic has currents which would try to move a stayed tube in various directions along its length and any change to these could potentially add stresses in cables and tube as would the various temperature gradients across the ocean. In the RN, we had to speed up and slow down condenser pumps whilst crossing the Gulf Stream so great was the difference in water temperature.
Definitely one for the fairy tales!

 

[HSTEd]

I don't know who could write a safety case to cover the operation of the tube or tunnel (once built). Just think of rescue arrangements in the Channel Tunnel then think of a tunnel thousands of miles long.....

The rescue arrangements for a transatlantic airliner involve a lot of pine boxes.
This is not significantly better than the ones available for a transatlantic tunnel - especially since buffer doors could be installed as required every couple of hundred kilometres.

If built and a safety case were to be achieved, any train running through a snaking, stayed, floating tube would cause the tube to flex so speed would not be likely to be very high.

The tube would remain in positive bouyancy at all times, otherwise it would sink. So the only snaking in the tube would be a result of the cables relaxing and stretching due to changes in load - as a train is relatively light this is sure to be a very minor effect.

Now, who's going to maintain the outside of the tunnel and inspect the stay cables in situ?

UUVs have come an awful long way in recent years.

Power transmission along the tube/tunnel would require many sub-stations to be spaced along the route.

That depends - if you used a standard 25kV supply system with conventional rails this would be so. But I doubt you would.

50kV-0-50kV AT would be the minimum, and I have heard talk that it would be feasible to build a 100kV pantograph if there was a need for it. At which point substation spacings will have reached the hundreds of miles. After all you would effectively be distributing power at 200kV AC.

You might only need two or three intermediate substations.
And since you will likely be using a conductor rail for reliability reasons - you have an enormous conductor cross section to use.

Volt drop would not be a major issue at 100-0-100kV and would be easily handled at 50-0-50kV (50kV is low risk as it is in operational use today)

To bring in another aspect, the Atlantic has currents which would try to move a stayed tube in various directions along its length and any change to these could potentially add stresses in cables and tube as would the various temperature gradients across the ocean. In the RN, we had to speed up and slow down condenser pumps whilst crossing the Gulf Stream so great was the difference in water temperature.
Definitely one for the fairy tales!

Yes, but the water temperature below the surface region does not tend to change much in the same location. Annual variations below 30-40m in the Atlantic tend to be measured in single digit degrees.
Static temperature differences over the structure are nowhere near the issue that thermal cycling would be.
And the currents don't tend to change much either - they tend to run in broadly the same direction at the same speed for much of the year - especially since in the deep ocean we can neglect tidal effects.

These are all simple engineering problems - they could be overcome if it was required that they be overcome.

 

[Class 170101]

How about earthquakes? How do you engineer for those?

 

[HSTEd]

How about earthquakes? How do you engineer for those?

You could use passive dampers on the ropes that removed low frequency vibrations - otherwise the obvious active solution is to have computer controlled winch drums attached to the tethers that allow the tethers to change length as required to dampen the effects on the tube itself.
After all the frequency is only a few hertz.

Since the (presumably steel cables) are multiple kilometres long over the areas likely to be affected by quakes it is entirely plausible that you could position sensors on the anchors that would report the commencement of an earthquake and the computer would be ready to respond before the shock had translated along them.

 

[8A Rail]

How did this thread get to four pages?? The mind boggles!

 

[ainsworth74]

Thanks to the three of you for some very interesting information on Soviet SSB's. From what I've read the Soviet's had the technology but ran out of money to maintain it.

That was the case by the end of the Cold War. Their early SSN and SSBN (ballistic missile submarines) were terrible. Dangerous to their crews* and very very noisy. The advantage we held was truly staggering. Plenty of stories of US and Royal Navy SSNs holding contact with Soviet Yankee class SSBNs for weeks and weeks (40ish days is the record) without ever being counter detected.

But they closed the gap (spurred in part by the information given to them by the Walker Spy Ring in the US) through the 70s and by the latter part of the 80s the Akula class SSNs were approaching levels of performance of Western SSNs (though still not quite as good). Of course the end of the Cold War and the economic collapse that followed pretty much halted their development so their still mostly stuck with their late 80s submarine fleets whilst we've moved onto the next generation. But certainly if the Cold War had continued it is likely they would have managed to catch up (or at least keep the gap much closer than it was in the early Cold War).

Though one advantage the US and Royal Navy would have had (and does have) is in the quality of the people in their submarines. The Soviets had some good people to be sure but ours were always of a consistently higher level thanks to being volunteer based rather than conscript based.

*najaB's joke would most certainly have been true if we'd been talking about members of the November or Hotel class.

As I understand things, the light shielding meant that the reactor was supposed to be automated since it was dangerous to work around for any extended periods. But the automation wasn't quite up to the task so people had to work in the compartment more often than was sensible. They probably avoided serious health consequences by rotating the reactor crews more often than they did with more traditional designs.

Ah I can believe that. Even it wasn't quite up to task the automation on the Alfa's was impressive. A crew of thirty compared with around one hundred on contemporary Royal Navy and US Navy SSNs.

 

[NotATrainspott]

You might be able to make it easy if you were building in sheltered waters - but I can assure you that doing so in the mid Atlantic in midwinter is an entirely different matter.

Your work boats will struggle to keep position and everything above water will be hit repeatedly by enormous waves.
Most proposals only assume work for half the year and going rather slowly at that.

And who said anything about boring out a tunnel? Just get the JCBs on the case - cut and cover tunnels in the middle of nowhere aren't very expensive, especially if you are willing to accept that the ground over the box is sufficiently shallow that all it will be able to support is turf.
And if you are running a saner, slower train in atmo at roughly 400-500km/h then you don't need a tube on land at all.

Just look at the specs for this so called "vac-train" - you can't have passengers pulling significant gs. It would never fly.

There wouldn't be a fleet of construction ships as much as a series of huge self-contained floating factories, each then being the base for a fleet of construction submersibles. Under the water, the weather above has little or no effect.

If you build on the surface, you actively need to change the earth all the way along the route of the tunnel. With a submerged tunnel, you only need to touch the ground when you need to anchor the cables, so the cost would be massively reduced.

Magnetic levitiation is the only feasible traction system for any intercontinental tunnel. After you evacuate the air, there would be no friction so once you've used energy to accelerate the vehicles, they'll just coast at that speed until you decelerate them. Where power might be needed along the tunnel it can be drawn from the ocean currents, so transmission losses would be irrelevant.

Inter/trans-continental maglev tunnels are like space elevators in that the massive upfront cost involved would be dwarfed over the long term by the reduction in transportation costs it would cause. The amount of energy needed to move one person from London to New York in an undersea maglev tube would be a fraction of the energy needed to move them by air. The economic impact of making it possible to cheaply move around the planet almost instantaneously would be extreme.

 

[HSTEd]

There wouldn't be a fleet of construction ships as much as a series of huge self-contained floating factories, each then being the base for a fleet of construction submersibles. Under the water, the weather above has little or no effect.

Yes, but what happens when your floating factories can't obtain more materials because the sea is far far too rough to actually dock and unload material from supporting ships?

Floating factories are probably impractical for this reason - it would be far more expensive than just tugging kilometre long sections out of a random Loch or somesuch.
Just use the same technologies as used for immersed tubes.

If you build on the surface, you actively need to change the earth all the way along the route of the tunnel. With a submerged tunnel, you only need to touch the ground when you need to anchor the cables, so the cost would be massively reduced

You think the cost of excavations is going to be a significant factor? I very much doubt it.

Magnetic levitiation is the only feasible traction system for any intercontinental tunnel. After you evacuate the air, there would be no friction so once you've used energy to accelerate the vehicles, they'll just coast at that speed until you decelerate them. Where power might be needed along the tunnel it can be drawn from the ocean currents, so transmission losses would be irrelevant.

What happens if something happens? These vacuum trains are essentially spacecraft - there is no mechanism to repressurise the tunnel fast enough to stop a decompressed vehicle suffering 100% fatalities.
If there is a containment breach for any reason everyone dies.
On land you can at least have squib valves to the air every few hundred metres.
And what happens if the trains stop moving for whatever reason?

 

[najaB]

The economic impact of making it possible to cheaply move around the planet almost instantaneously would be extreme.

Personally, I'd rather that humanity invested the hundreds of billions of dollars/euros/pounds/yen/roubles/rupees/reais into getting Q to be greater than unity (while being able to reuse the apparatus).

 

[NotATrainspott]

Yes, but what happens when your floating factories can't obtain more materials because the sea is far far too rough to actually dock and unload material from supporting ships?

Floating factories are probably impractical for this reason - it would be far more expensive than just tugging kilometre long sections out of a random Loch or somesuch.
Just use the same technologies as used for immersed tubes.

When you have the technology to build a transatlantic tunnel, the technologies to make a floating factory aren't going to be that far-fetched.

You think the cost of excavations is going to be a significant factor? I very much doubt it.

Yes, it is going to be the most significant cost of any land-based tunnel. Tunnelling is expensive and always will be.

What happens if something happens? These vacuum trains are essentially spacecraft - there is no mechanism to repressurise the tunnel fast enough to stop a decompressed vehicle suffering 100% fatalities.
If there is a containment breach for any reason everyone dies.
On land you can at least have squib valves to the air every few hundred metres.
And what happens if the trains stop moving for whatever reason?

It's exactly the same then as supersonic, hypersonic or space-based intercontinental travel. To make the tunnel worth building, the air pressure inside would need to be low enough that any rapid decompression would kill all the passengers before it would be possible to slow down from the very high speeds (measured in kilometres per second) that the vehicles would run at. Passengers on Concorde would have lost consciousness within six seconds so they weren't even provided with oxygen masks. The pilots' oxygen masks were to force air into their lungs, giving them enough time to put the plane in probably the fastest and steepest descent that you could ever describe as being 'controlled'.