New York to London in an hour - by train • Hacker News Board

Re: New York to London in an hour - by train

#121

Post by redwood » Wed, Jun 13, 2012, 8:22 AM UTC

ChuckMcM wrote: post #11

Good luck holding a vacuum under the ocean. I read stuff like this and I think, "Gee, I don't think these people have actually built anything." because if they had they would realize that if it costs $1M a foot too build subways [1] in cities with moderately skilled labor, its going to cost $10 - 25M/ft to build something like this. That's half a quadrillion dollars (448 trillion dollars). What sort or rate of return…

A vacuum only weighs 1.28 grams less per litre than air. Since there are 1000 litres in a cubic meter, a 3x3x3 meter cube (approximation of a cross section of a unit of the tube) would contain 27000 litres whose air would weigh 76 lbs.

In other words you're talking about sinking 3 meters of tube that would weigh 76 fewer pounds than if there were air. This is probably a small effect compared to the weight of the strong metal casing that would need to surround such a vacuum.

So since we can sink normal air-filled subways quite normally (e.g. the BART in San Francisco) this must be a well-established technology.

Re: New York to London in an hour - by train

#122

Post by tomelders » Wed, Jun 13, 2012, 9:06 AM UTC

evoxed wrote: post #93

citricsquid wrote: post #7

Earlier quoted context omitted.

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.

Re: New York to London in an hour - by train

#123

Post by MortenK » Wed, Jun 13, 2012, 9:07 AM UTC

blehn wrote: post #107

melling wrote: post #55

I live in NJ, about 4 miles away from my office in Manhattan and I have a 45 commute. Can anyone figure out how to solve that problem? It's a lot of fun to kill the afternoon talking about something that's never gonna happen. In the meantime, millions of people are wasting days a year crawling to and from work.

that's an easy problem to solve. you could either a. move your home closer to work b. move work closer to your home c. move both you're traveling 4 miles, across a river, into one of the most densely populated cities in the world. there's bound to be some friction. that said, you could probably live 4 miles away in brooklyn or queens and be at work in 15-20 minutes.

That's simple solutions, not easy ones.

Re: New York to London in an hour - by train

#124

Post by corin_ » Wed, Jun 13, 2012, 9:11 AM UTC

archangel_one wrote: post #50

corin_ wrote: post #26

Earlier quoted context omitted.

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.

Re: New York to London in an hour - by train

#125

Post by DeepDuh » Wed, Jun 13, 2012, 9:13 AM UTC

SoftwareMaven wrote: post #88

DeepDuh wrote: post #65

Earlier quoted context omitted.

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)?

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 :).

Re: New York to London in an hour - by train

#126

Post by lmm » Wed, Jun 13, 2012, 9:26 AM UTC

rogerbinns wrote: post #82

moystard wrote: post #69

Earlier quoted context omitted.

The disadvantage of your solution is the environment impact of such a transportation system. An electricity based solution seems to be much cleaner (especially if we imagine the same kind of traffic as the plane one today).

Couldn't you use electricity to separate hydrogen and oxygen from water, and then "burn" that in the rockets to produce water again?

You can, but under current technology this is a lot less efficient (I remember hearing a 12% figure somewhere) than direct-drive electric motors.

Re: New York to London in an hour - by train

#127

Post by newbie12 » Wed, Jun 13, 2012, 9:27 AM UTC

anamax wrote: post #113

excuse-me wrote: post #49

Earlier quoted context omitted.

Of the $80M/mile - $70M is to buy the land and pay off objectors, $9M is security and fencing for the work site and $1M is to build the actual track. The nice thing about a transatlantic tunnel is that crustecaeans can be bought off cheaply

> The nice thing about a transatlantic tunnel is that crustecaeans can be bought off cheaply The various environmental organizations aren't going to be bought off cheaply.

This tech is far better for the environment than the air travel it would displace.

Re: New York to London in an hour - by train

#128

Post by UIZealot » Wed, Jun 13, 2012, 10:27 AM UTC

Doesn't a gravity train actually seem more appropriate here? It doesn't need to go through the center of the earth in this case, and is shorter distance than a tunnel. The only problem is it probably takes a lot longer to build.

Re: New York to London in an hour - by train

#129

Post by rfugger » Wed, Jun 13, 2012, 10:33 AM UTC

planetguy wrote: post #67

allenlavoie wrote: post #64

Earlier quoted context omitted.

Is there some reason that sandwiching air between the evacuated tube and the water wouldn't work? Granted it would add to the cost. The ocean depth point is interesting. The article says "engineers would tether the tunnel at a fixed depth." I take this to mean tethering to the bottom and relying on buoyancy to keep the tunnel floating at the right depth, which presumably could be 30m or so.

>Is there some reason that sandwiching air between the evacuated tube and the water wouldn't work? Yep, because now you've just got your air rushing into the vacuum through the cracks, instead of water. The ocean depth point is interesting. The article says "engineers would tether the tunnel at a fixed depth." I take this to mean tethering to the bottom and relying on buoyancy to keep the tunnel floating at the right…

Some kind of gel between the layers perhaps?

Re: New York to London in an hour - by train

#130

Post by crististm » Wed, Jun 13, 2012, 11:33 AM UTC

redwood wrote: post #121

ChuckMcM wrote: post #11

Good luck holding a vacuum under the ocean. I read stuff like this and I think, "Gee, I don't think these people have actually built anything." because if they had they would realize that if it costs $1M a foot too build subways [1] in cities with moderately skilled labor, its going to cost $10 - 25M/ft to build something like this. That's half a quadrillion dollars (448 trillion dollars). What sort or rate of return…

A vacuum only weighs 1.28 grams less per litre than air. Since there are 1000 litres in a cubic meter, a 3x3x3 meter cube (approximation of a cross section of a unit of the tube) would contain 27000 litres whose air would weigh 76 lbs. In other words you're talking about sinking 3 meters of tube that would weigh 76 fewer pounds than if there were air. This is probably a small effect compared to the weight of the stro…

It's not about vacuum being weightless. It's about vacuum being an active stress factor for the entire construction.

It will _want_ to collapse. It's not sitting there doing nothing.