> Also, easy terrorist target.

What a shame this determination is made on so many "advancements" now.

(I think it's complete nonsense to even mention)

Before the terrorists it was the Communists - people are just contrarian.

in this case the blogspam serves a purpose, accessing the bbc.com story:

"We're sorry but this site is not accessible from the UK as it is part of our international service and is not funded by the licence fee."

Wait, what now? You're blocked from reading a story, from inside the UK?

I'm as shocked as you are. As a licence payer, I'll be sending a strongly worded letter to the management.

Which terrorists are you worried about?

If al Qaeda blows up a pressurised train tunnel, then yes they can kill lots of people, heap a big cash cost on the tunnel operator... but they don't get any impressive pictures to put on TV.

If the IRA/ETA/etc blows up a pressurised train tunnel, they impose a big cash cost on their target, plus cause lots of disruption... but in terms of effort/risk/reward it's probably better for them to blow up conventional rail/road infrastructure in London/Madrid/wherever.

What makes current train system a more difficult target than these tubes?

Scale of attack, amount of force required, social and economic impact of the accident.

Look over a list of who the victims of the Titanic disaster were -- comparable in that it was the luxury travel alternative of its day. Jay Jacob Astor, Benjamin Guggenheim, Ida Straus (founder of Macy's), just to name a very few. The societal impact of the Titanic's loss was ... titanic.

You wouldn't even need an explosive to foil the tube. Simply something to perturb the system slightly would disrupt it in a bad way. Even if only a single small transport were in the vicinity, any others in the tube would also be doomed (granted, at 1 hour/trip, headways would likely limit this to a very few instances).

Trains are very robust. Conventional high-speed rail is a bit riskier, but even accidents such as on the German Eschede rail disaster (at 200kph) saw over 60% of the passengers survive: https://en.wikipedia.org/wiki/Eschede_train_disaster

Strikes me more that the potential for damage is higher here. A pretty small explosive charge would compromise part of the tube, and then what happens to the pods zipping along at 2,500mph inside them when the air comes rushing in? For that matter, if they did have an underwater tube connecting London and NYC, the water would come rushing in and you know that's not going to end well.

It sounds pretty cool - it's the kind of sci-fi thing I'd love to see in the real world, but I can't believe it's as easy or as cheap as they're making it sound here.

We already have underwater tunnels for trains, such as the one between England and France - water would come crashing in regardless of whether there is air or a vacuum in the tunnel.

It's not actually Futurama, the tunnel won't be train-sized and made of glass.

The chunnel is technically under rock, not under water. It's not exposed to the ocean.

Surely any tunnel built will be surrounded with rock/concrete as its structure, ultimately it will still be a case of people surrounded by solid material surrounded by water.

They aren't going to dig a tunnel through rock all the way underneath the Atlantic - that's many times further than the Chunnel, and that was a serious undertaking. The article implied it'd be underwater.

The tunnel itself will be formed of solid material, they don't need to go underneath the sea bed they will put their own construction in. That is what the tunnel will be, it's not just a vacuum in the middle of the water.

Obviously the tube would have to be incredibly strong, since it will have to withstand the water pressure at whatever depth it's at. I'd be curious to see calculations on that, as well as repair costs. Also costs for land-based vs sea-based.

Not a more difficult target, just less of a damage multiplier, I suspect. Even in the high-speed train crashes of today deaths aren't too high. A train travelling at 2,500mph, however...

Really, how is this any different from airplanes? Just use equivalent security measures.

Also, I wonder if it would be possible to have more frequent, smaller trains, e.g. airplane-sized. Then it doesn't seem like terrorism should be any "extra" consideration at all.

Well, airplanes are a considerable distance up in the sky and incredibly difficult to reach. It's why the vast majority of plane-related "badness" happens shortly after takeoff or shortly before landing. Any land-based rail vacuum tunnel would not be protected in this way. An underwater one would be to an extent- I suppose it depends how deep it goes. But it's still a lot easier to drop something (say, a bomb) into water and let it sink than it is to fire it into the air and hit a plane.

5 times the speed = 25 times the kinetic energy (per kg). And that is for the 'slow' one. At 4000mph, it is more like 64 times. And yes, this only talks of a 6-person capsule, but I think you would need to send quite a few of them through that tube to make it economically feasible. You wouldn't need to bring explosives to destroy the tunnel. Just have enough to have a 10 kg or so part drop from one of those capsules.

Safe to say that the terrorists have won, if the first eight comments on something as cool as this have to do with possible ways the terrorists can destroy it. What a depressing new era.