The Future of Sucking: Vacuum Express Train, NYC to Philly, 1945

JF Ptak Science Books    Post 1315

 

John B. Prather launched an idea in 1945 for building a high-speed pneumatic passenger/freight train connecting New York City to Philadelphia.  His New York-Philadelphia Vacuum Tunnel, Preliminary Design Features and Economic Analysis (the original available on our blog bookstore) was exceptionally hearty. The idea is interesting in a removed, lets-not-do-it way because, well, it just doesn't seem to make sense in the long run, at least beyond the building of the thing to show that it could be done.  And I don't doubt that could be the case--I just don't know why it was necessary. 

Mr. Prather's approach seems to be the work of an engineer, or at least he had some help.  I doubt though that he had any help from a structural engineer or site geologist--his proposal was to build this tunnel 100' down through bedrock when it could be found, a level hundred-feet  below the surface, from NYC to Philadelphia.   The tube would accommodate an aluminum-shelled  400'-long train that would be hauling 350 people and 175 tons of freight at speeds of 400-600+ mph, making the run between the two cities in about 20 minutes.  Not bad.  He figures too that all of the freight could be offloaded in 7.5 minutes.  This would make for  a very busy train, though Prather doesn't tell us how many runs a day it would be making. This was all preliminary.

The 16.2'-wide  tunnel would be 456,720 feet long, and would cost $173 million to excavate and $41 million to line with cement--according to the author.  The total cost for the ordeal would be about $334 million and would take 6 years, start to finish--that includes all of the tunneling, which would swallow/excavate/face 300' per day. 

I don't see, really, how this could be so narrow a tunnel--I'm not an engineer but it would seem that wear, heat and the abuse and so on that a massive and dense 400'-long missile going 400+mph would require something that was more than 125% of the width of its trains. 

There is however  precedence for a massive tunnel of something like this size being built in something like this time--the Delaware Aqueduct is 82 miles long and 13 feet wide, and was built during the Second World War (1939-1945) , so, perhaps if enough people and money were thrown at a project like the vacuum tunnel could actually be built (barring geological problems). 

But it would all be worth it:  Prather suggests that the overall revenue from the operation of the train to be $196 million/year with $32 million in yearly operating expenses.  Which means that the whole thing could be paid for in three years or thereabouts.  So if the things was started in 1946, it would all be finished and paid for by 1956.

I can understand his thinking, though, especially when you consider the impact of the year (1945) in which this paper was written.  The U.S. was came away from WWII by far more strong than any country on Earth, with its GDP being about 50% of that of the entire world--on the other hand, the federal deficit was 125% of the GDP, so perhaps in addition to being in an extraordinary position, investment was also somewhat gunshy.  And of course there's the problem of whether Prather's idea made any sense at all.  But I can understand the high times during which his project was announced. 

I've looked at a number of proposals like this over the course of this blog--like almost filling up the Narrows between Staten Island and Manhattan with an airport and seaport, and making a series of transoceanic airports for flights between the continents, and dropping a gigantic shell filled with people from the top/interior of the Eiffel into a narrow hole filled with water, and covering Midtown Manhattan with a rooftop airport, and covering Midtown Manhattan with a glass-ish dome, and so on--and I know that it is good for at least one thing:  superb classroom discussion fodder of why something like this does or doesn't make good physical/economic etc. sense.

 

 

Comments

[Jeff Donlan]

Vacuum for propulsion doesn't make much sense, since with a vacuum the most pressure differential you can get is one atmosphere, applied to a very small area at the back of the train. However, vacuum or some kind of powerful venting would be required in front of the train, since at those speeds it would build a remarkable pressure ahead of it in it's narrow tube. Maybe it would be named Spitball? Turbulence might be a problem. Does the pamphlet address any of this?

[John F. Ptak]

Jeff--I think that the guy had some idea for different ends of "pulling" the massive thing through his tubes via a power source on one end; there's also a scheme for electromagnets. But the details for the idea were not committed to print--its a sprite of an idea with more printed planning for ho wmuch stuff would cost and how much the whole thing could "make" than anything else. Lets face it--Columbus didn't have a very good plan, either, and most of that was in his head. When The Captain figured out that the trip to the far Asian lands would be--reckoning by degrees--very far away, he did what other determined people would do. Columbus recalculated how many degrees there were in a mile. And he got that down t about half of what it was reckoned to be. Thus the distance issue was settled. And I think in many ways our author for the vacuum tunnel was like that, too, and that is the thing that makes this paper have an "author" rather than a "reporting engineer". Your points are very good--and this is precisely why things like this should be studied in school, because in order to know if an interesting/arresting idea is goofy or not, you've got to figure out the "why" part.

[Jeff Donlan]

But now I get it a little more. The vacuum was to reduce friction and aid propulsion, like traveling at tremendous speed in space, so that it becomes conceivable to get NYC<>Philly in 20 minutes through a soda straw. Now, if everyone would just cooperate and board and take their seats within 2 minutes, we could have something here. But it's like those short commuter flights: getting to the station, descending 100 feet in a crowd, pausing to listen to a musician and then fish for some change, boarding in a crowd and offering your seat by the door to an old lady and she says no you don't have to and you say but of course I must and you exchange smiles and help her sit down, then waiting to clear the tunnel of skateboarders who found an unlocked door ... well, we haven't even left yet and it's taken more time than the trip itself. Anyone on the Philly side of NY would probably just drive. And now, we have the Internet, with both electromagnetic propulsion and it's own kind of vacuum.

[John F. Ptak]

I started to write more about this but I began to bore myself, which means I'm sure I'd've lost everyone else along the way. I wasn't so sure about getting to and breaking from 600 mph in the hundred miles or whatever between NYC and Philly. Seems to me that you could go 600 for only, what 5 minutes, so it would be 5 min to get to 600 and 5 mins to brake. At least the tunnel is supposed to be perfectly straight except for entering/exiting cities.

[John F. Ptak]

And by the way, how are we going to create a vacuum for the 81 million cubic foot tunnel