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Comment by moocow01 | Hacker News Reader

I never have understood people's fears about getting on an airplane... this though I'd be scared to death of. You have any unfortunate shift in the tectonic plates (which happens daily and unpredictably) and you could be dead in an instant.

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I gather that the intent is to tether the tunnel. I've seen how cables are run in tectonic-active areas: they are provided a certain elasticity and I imagine it would be similar. Earthquakes don't move much more than a few meters at a time (for a very very large event). How would this be any different than the Chunnel?

My own comment on this article: "getting to, from and through airports is very time consuming"

I don't see how this would be any less time consuming. Security would be an equal nightmare - the only benefit would be that the citizens can utilize NYC/Londons existing transport infrastructure much like it's easier to get to the Chunnel departure station than it is to get to Gatwick.

The Chunnel doesn't cross a fault line.

Perhaps nothing considered imminently dangerous but they do exist nearby, and fault lines can spread given the right conditions: http://www.esri.com/news/arcwatch/0210/graphics/investigatin...

Oh, yes, security! Strange this isn't discussed more. While a bomb in an airplane is bad enough imagine what a ripped vacuum tube under the ocean will do! Such a tube will be a high profile target for terrorism and an incident/accident would block/destroy the whole traffic.

Here's how the Japanese high speed trains deal with earthquakes: They have emergency break systems (I think its small ceramic globuli or something of the sort) and a really good forewarning system. 2011-3-11 all Shinkansen were at a halt when the big one hit and noone was harmes on them. I don't see why you couldn't do the same here.

Because if the rail line cracks (which probably did appen in Japan), water floods into your tube. Then it becomes a question of "can they rescue you before your air supply ends" (since they would require an air supply for the vacuum)?

Oh, this post was in reply to the underwater part? Yes, I also think that this one isn't feasible for quite some time. My reply was in response to vacuum tubes over sea level. Right now we can't even have floating tubes anchored to the sea ground yet; storm waves rip every anchor we can build apart (it has been tried for wave power generators).

Vacuum tubes could probably be built deeper down where the waves aren't strong. I actually think that earthquakes wouldn't necessarily be a problem at that level, since everything would have to be quite flexible anyway. In order to elevate security, I could imagine making tube sectors detachable and having safety shutters. This way, if one sector is breached it could be sealed and detached such that it floats to sea level. The train could even be inside if you can control the pressure differences well enough to not kill everyone inside (something that is well understood for jet planes).

Since it's an interesting mindgame I thought about it a little further: There IS a hard problem to solve here: If your train takes 5min to stop from 4000km/h, its breaking distance would be 166km (assuming linear deceleration)! This means that you could only shut down sectors further away than 166km from the closest train - all sectors within are your vulnerable zone. That seams quite risky to me. On the other hand we do fly millions of people a year in pressure cabins with no way to escape. Since with this new system people's life would depend on tubes 160km long instead of 70m (length of a 747), all you need is materials that are 2000 times more reliable than those of our jet planes. While being emerged in seawater. And enduring a much higher pressure difference. Yeah.

I'd say let's wait and see what nanotechnology gives us :).

Wouldn't emergency brakes pretty much kill you if you're traveling a few thousand mph at the time?

Good point. Obviously you would have to restrict the applied g-forces, therefore the time to stop would be longer. If I'm not mistaken, this should only a linear relationship though, e.g. if you restrict the acceleration, the time to do 10x delta_v is 10x the time you need for delta_v. As long as the earthquake forecast is good enough, this should be manageable, e.g. you need 300 seconds instead of, say, 30. 5 minutes forecast seems realistic to me. Obviously you can never give 100% safety - if the epicentre of a big quake is right underneath your trainline you might be screwed; However that chance is really small and we already live with these kinds of risks today.

I think the main issue is being trapped in an airless tunnel several hundred feet under the middle of the atlantic ocean. That is a far cry from 'train stopped on tracks in the middle of a field'. Frankly a stopped train sounds like a great place to ride out an earthquake - far better than many buildings.

Speaking as someone who hates flying, it's not the general concept of death that scares me, but everything leading up to it.

> you could be dead in an instant

You have your answer right there.

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