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Why Ultra-Efficient 4,000 mph Vacuum-Tube Trains Aren't Being Built
cylonlover writes "In the 1800s, when pneumatic tubes shot telegrams and small items all around buildings and sometimes small cities, the future of mass transit seemed clear: we'd be firing people around through these sealed tubes at high speeds. And it turns out we've got the technology to do that today – mag-lev rail lines remove all rolling friction from the energy equation for a train, and accelerating them through a vacuum tunnel can eliminate wind resistance to the point where it's theoretically possible to reach blistering speeds over 4,000 mph (6,437 km/h) using a fraction of the energy an airliner uses – and recapturing a lot of that energy upon deceleration. Ultra-fast, high efficiency ground transport is technologically within reach – so why isn't anybody building it? This article looks into some of the problems."
Yes, like aeroplanes and submarines...
If you don't reach for the stars you will never get there, if you try, you might.
The article mentions this... the problem is, it sets up a false dichotomy. The options aren't no vacuum trains or ones that go at 4k mph... there is a whole range of speeds that these trains could be effective and efficient, and not all will turn passengers into goo if it crashes.
while(1) attack(People.Sandy);
Someday maybe the Japanese can figure out how to build a bullet train in an earthquake zone.
Because the simple-minded mythology that people create for themselves is just that: feel-good pseudo-engineering that makes no sense whatsoever.
For an AC that was a brilliant post. However a little brief. As a "real engineer" who can do estimation and think thru technical problems the biggest problem is the vacuum tube is a waste of money and time and land. For a much smaller scale example you could reduce the "indicated air speed" as a pilot would call it of the TGV in France merely by installing gigawatts worth of walmart kitchen fans pointing such that the train gets a nice tailwind. However if you run the numbers it turns out you can get the same performance increase with merely megawatts of extra train power. Similarly, you could invest in terawatts of distributed vacuum pumps, but it turns out you can go just as fast merely by using gigawatts of train power...
Generally speaking in engineering making the immense part more expensive to make the little part cheaper doesn't pay off, for sufficient value of immense. For example, it turns out to be way the heck cheaper to make a long distance transmission line HVDC than to upgrade every tower long the route higher dielectric strength and taller and bigger footings etc etc. To a crude first approximation this is why sea transport is cheaper per ton-mile than train transport. Another example in the US outside hyperurbanized areas its cheaper to buy each user a taxi and taxi driver than to build passenger rail. I like trains and I like riding in trains but even I realize they're an economic disaster.
In fact it turns out to be cheaper to build a self-levitating and self propelling vehicle than to build a really long and terribly complicated track. I think I shall call my new invention the aeroplane.
The other problem is economic. Any 4000 MPH solution is terrifyingly expensive, so even zero interest expense makes it horrendously expensive. If you can get it cheaper than merely hiring someone far away, or booting up a PC running skype... For example, even during the Concorde era it didn't make financial sense to ship a salesman between NYC and London on the Concorde, it turns out to be cheaper to simply open a sales office in both cities and hire staff in each. Somehow this tremendously more expensive solution is supposed to work even better under conditions where cheaper solutions miserably failed?
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
A run from NY to LA would run you several billion dollars just to get started and several hundred million every year after that for maintenance and repair. So, the real question is: is there enough traffic between NY and LA (for example) to recuperate the cost of construction and operations. I highly, highly doubt the answer is yes.
If it were that cheap it'd be "yes, absolutely, and we're going to hook up every major city as well."
They're talking about spending over $150 billion for the high-speed rail from San Francisco to Los Angeles, and Amtrak's discussing $100 million in track improvements to get TGV-level speeds from Boston to Washington, DC.
Those are the nicest train routes in the country, but they're peanuts compared to how profitable a NY-to-LA in under an hour route would be if it only cost a few billion to get going and several hundred million a year to operate.
rage, rage against the dying of the light
Trains are an economic bonanza in the US. Freight trains are still trains.
Limit your comments to passenger trains, and you might think it is true. Then you realize they're competition g with heavily subsidized highways.
At those speeds, flames would be the least of your worries. a 20,000kg train at 6400kph carries the kinetic energy of a 8,000kg of TNT (31GJ). It would take 3 minutes to get to that speed with a constant 1G acceleration and require a 17MW output engine, and would travel 160km while getting up to speed.
The point is things like planes weren't possible until gasoline engines, very quickly powered flight went from impossible to possible due to one technology and some smart people.
So:
1. Don't stop dreaming
2. Your Religion of Pessimism is just as bad, so STFU
Trains work in the US when shipping freight. The work for passengers in the northeast. However, cars are far more convenient everywhere else.
Case study:
Trip to Norfolk, VA from NYC area.
Fly: ~$300 per person round trip. You get one carry-on bag per person. 1.5 hrs each way + 4 hrs of transit/wait time.
Train: ~$250 per person round trip. You can carry more on. 8 hrs each way + 2 hrs of transit/wait time.
Car: ~$75 per car round trip. You can carry even more. 6 hrs each way; no wait time.
Now, if I didn't already have a car with sunken capital costs, then there is an argument. But even then, I would rent a car. Either way, it is cheaper and takes less time to drive than take the train.
In contrast, it would be crazy to drive into NYC when the train station is right next to where I am. Flight is almost always better if time is a factor.
And don't tell me "it's different in Europe". I was in Germany. I can drive from Munich to Berlin faster than the ICE train. And the train ride costs $150+ each way per person.
Outside of heavily subsidized metro area trains, I have not seen a train compete with the cost, let alone the time and convenience of driving alone. When you add a 2nd person, it just gets crazy to take a train.