Wednesday, November 25, 2009
The advantage of a mag-lev train moving in vacuum is that it has effectively no friction restraints. It can thus move at any speed, far faster in theory even than stratospheric jets, & that since there are no energy losses in movement, though there are in accelerating to that speed, running costs are very low. Disadvantages are that getting in and out is a fairly complicated process & turning tight corners at that sort of speed not pleasant (though if cornering the train can tilt & since there are no windows all you would feel is a slight increase in gravity pressure which is kinda cool). Accelerating at 1 g (10 m/s^2 = 22mph acceleration a second would mean it takes 45 seconds to accelerate to 1,000 mph by which time one has covered 6.20 miles). Since that acceleration is horizontal while gravity is vertical the combined G would be 1.41 which is perfectly acceptable sitting down, though seats would have to turn round before deceleration at the end. However it means that this is a system which would be optimum only for long distance travel. The other disadvantage is that building hundreds or thousands of miles of tunnels & keeping them airtight is not cheap. Vacuuming is probably not as big a problem as appears because it is only a 1 atmosphere pressure differential & engineers regularly work with thousands. Where air travel is the only competitor it is an option worth looking at.
A vactrain is a proposed, as-yet-unbuilt design for future high-speed railroad transportation. This would entail building maglev lines through evacuated (air-less) or partly evacuated tunnels. Though the technology is currently being investigated for development of regional networks, advocates have suggested establishing vactrains for transcontinental routes to form a global subway network. The lack of air resistance could permit vactrains to move at extremely high speeds, up to 6000-8000 km/h (4000-5000 mph or 5-6 times the speed of sound at sea level and standard conditions), according to the Discovery Channel's Extreme Engineering program "Transatlantic Tunnel".The optimum first development would be something 200-300 miles long connecting really large & wealthy cities separated by sea & thus currently only accessible by air. Japan, Seoul, Beijing are slightly further apart than that but not a bad fit, between some of the Japanese islands are a shorter distance. Since this is tectonically active I would need some convincing however.
Theoretically, vactrain tunnels could be built deep enough to pass under oceans, thus permitting very rapid intercontinental travel - wiki ctd
My other suggestion is from London. There is already a tunnel connecting it to Paris, 2 of the world's great cities but an alternative would be connecting to Amsterdam, still a major city & one where English is almost ubiquitous. A straight line from there passes just north of Berlin & then Warsaw. It would require some bend to extend it to Moscow (1500 m) but there is a lot of room to manage it. Rail's major problem for the commuter is that it goes only to very restricted locations. Hour & a half from the centre of London to that of Moscow is pretty wonderful. Even an hour in traffic at each end making it 3 1/2 hours from Brent Cross to Krylatskoe isn't shabby.
Vac-trains have been proposed before. In the 1970s Robert Salter suggested
A route through the Northeast Megalopolis was laid out, with nine stations, one each in DC, Maryland, Delaware, Pennsylvania, New York, Rhode Island, Massachusetts and two in Connecticut. Commuter rail systems were mapped for the San Francisco and New York areas, the commuter version having longer, heavier trains, to be propelled less by air and more by gravity than the intercity version. The New York system was to have three lines, terminating in Babylon, Paterson, Huntington, Elizabeth, White Plains, and St George.
The killer argument against
In Salters day "Enormous construction costs (estimated as high as US$1 trillion) were the primary reason why Salter's proposal was never built" which is hardly surprising when the entire US economy was only a couple of trillion.
Here also is a link to discussion of the idea - it gets a rough ride but that is what such discussion is for.
However times & technology change. Tunnel boring technology in particular. Between 1982 & 2000 Norway built over 750 km of tunnels at between £3.2 million & £10mill per km. London-Amsterdam is 356 km. At an average of £6.6 million X 2 tunnels come out at £4.7 billion. Double that for airtighting & double it again for track & because everything costs more & takes longer (#119) we come out at £20 billion. That is not a sum to take lightly though it is less than the proposed high speed rail link between London & Scotland which many favour, though I do not.
Even if it isn't profitable it may be financially viable in terms of how it enhances property values. That is why the cold-hearted and calculating property developers at Canary Wharf offered to pay for the entire Jubilee Line extension themselves. They did their figures and worked out that £400 million spent on the extension would have boosted the value of their office blocks by over £1,000 million.. A few years of world average economic growth would certainly expand the market. Moreover technology didn't stop in Norway in 2000. I don't know if tunneling costs have further reduced but it is certainly possible & I can imagine that it would now be possible to build a better tunnel borer, better than this tiddler
possibly even run by one of Hyperion's reactors, which would chew through ground steadily at a much reduced price. If it doesn't exist now it is the sort of technology bottleneck which could be considerably eased by an international technology prize. Also there should be economies of scale in longer tunnels. Indeed looking at the falling cost of tunneling & the ever increasing share that lawyering plays in getting permission to build on the surface, which contributes to the £26 billion price of a London-Scotland high speed train, we may well be close to the stage of crossover.
Finally an idea which is not entirely mine, I wrote of it here, but has not been applied to such trains - just as accelerating a train takes electricity, deceleration produces current. Such power can be stored with high efficiency in flywheels which can, in turn, power that train starting on the next stage or another in the opposite direction. If so energy costs are pretty much limited to the inherent inefficiency of any system. Not only the fastest transport in the world but +80% of the energy reused as well.
UPDATE Colin McInnes has sent this link to an alternative which, by boring through the centre of the Earth allows for gravity to provide the motive power. However with flywheels already saving approx 80% of the power I think the energy costs of core cooling would significantly exceed the saving. We will probabnly have to make do with taking the long way. http://www.mprize.org/?pagename=mj_mprize_learn
On such concepts it would be theoretically possible to accelerate the train to above 16,000 mph. This, at 1G acceleration would take 12 minutes & a distance of 1,600 miles. Because of the rate at which the train would drop due to the Earth's curvature beyond that speed we would perceive negative gravity. This could be obviated by the train swinging over & running on the roof. At 1 G acceleration for 6,000miles & the same deceleration we could reach Australia in 47 minutes, reaching a peak speed of 31,000mph and achieving a maximum negative gravity of 93% of normal gravity. This is only 5 minutes longer than the direct route. Heinlein's book Friday contains this method of transport though for lesser distances & speeds.
Like all projects of this type it's not the technical matters that get in the way but the responses of the 'do gooders'. Just look at the flack at NASA by the loony left - think of all the people the money spent on getting to space could have helped. What they ignore is all help for people by the spin off applications.
The other thing they should be considering for the high speed link to Scoyland is an elevated maglev line.
I doubt if the direct energy cost would be a big factor in overall cost, or indeed to the energy cost of frictional losses in current long distance travel but you would be able to estimate them better than I. There is also the possibility of recapturing the energy through magnetic braking.
You are right about a submerged Atlantic tunnelm which would be expensive per km compared to burying it. The Mid-Atlanmtic Ridge makes a buried tunnel impossible. After everything else had been built it might get funded on the basis that it was needed to allow a continuous loop round the world. I certainly wouldn't start with the big bits.
Ny assumption about a submerged tunnel costing more is because they currently seem to be more expensive than the Norwegian tunneling. However we are talking about comparative costs between 2 progressing technologies at an unspecifiable point in the future, made more complex by the fact, as my other articles on Norwegian tunneling show, that the overwhelming cost of engineering projects here, by a margin of about 12 to 1, is not the technology but the cost of squaring the politicians.
I agree that a transatlantic tunnel would be the last bit, worth it only after the connecting infrastructure was in place.