Could this be the new railway (minus the rails) of the future?

[Bob Bufkin]

http://translogic.aolautos.com/2013/07/12/zero-to-4-000-miles-per-hour-in-3-minutes-hyperloop-travel-coul/?icid=maing-grid7%7Chtmlws-main-bb%7Cdl28%7Csec1_lnk3%26pLid%3D344507

[lock4244]

Dunno... still waiting for those flying cars and vacationing on the moon to come to pass.

[jagged ben]

I've seen articles on this before, along with criticism.  There are some serious engineering and safety issues with traveling 4000mph on the surface of the earth, regardless of the technology.  One problem is g-forces in curves; I believe turning radii would have to be measured in miles.   And then there's what happens if there is any kind of 'derailment' or collision, or a pressurizing of the vacuum.   Basically, don't bother wearing a seatbelt, because if anything does go wrong, you will be splatter regardless.   Also there could be a serious release of energy (i.e explosion) that affects a wide radius of the surroundings, and probably cause enough damage to shut down the system for a long time.  Do the resources existing to construct such a system for a price that makes such risks worth it?  I think it's doubtful.

I think we have a physicist or two on this board, maybe more knowledgeable comments can be made.

[nkalanaga]

4000 mph = 6400 kph = 6,400,000 meters/hour
= 1777.8 meters/second
=9.876 m/sec^2
= (close enough) 1g

Basically, sitting in a standard seat, you'd feel 1.4 g at a 45 degree angle down and back during acceleration, and down/forwards if they slowed at the same rate.  Acceleration wouldn't be a problem, but you'd either slide out of the seat or have a very sore belly from the seat belt when stopping.

[GaryHinshaw]

Obviously there are lots of challenges here, but one of the biggest is the network of evacuated tubes required to transport these trains.  Just how do the trains (and people) get into and out of these tubes?  Not sure how much of a vacuum they are considering, but that will be a bugger to maintain (and expensive to build!).

I'm not sure how popular such a ride would be from the standpoint of creature comforts.  4000 mph in 3 min is an average acceleration of 1 g (probably no coincidence -- for comparison, a respectable sports car that goes 0-60 in 5 sec has an average acceleration of ~0.5 g.).  This means that passengers will have an effective weight that is sqrt(2) times larger than their rest weight (e.g. a 100 kg man would feel like 141 kg for a full 3 min at the beginning and end of the trip.  Also, you'd probably have to spin the seats to face backwards for the deceleration, otherwise you'd be asking the seat belts alone to bear the equivalent of your full weight during deceleration, which would be very uncomfortable.  I bet some fraction of the passengers become nauseous during the trip.

There would also be a small Coriolis acceleration (due to the Earth's spin) that would produce transverse accelerations of order 0.05 g, which would make you feel like you're constantly turning to the left or right (depending on whether you're going east or west).

Added - good to see that nkalanaga gets the same answers. 

[peteski]

Such a negativity from both all three of you!  This is a new and innovative up-and-coming technology. Give it a chance!  Why are you guys presenting factual numbers that stack up against it?  With this kind of attitude, you guys should be posting in the N scale magnetically coupled air hoses thread! 

[C855B]

All I can visualize is a Twilight Zone-esque scenario where you get into one of the capsules and the end of your trip is a giant bank teller at a drive-up window.

Check out this Wikipedia article about Col. John Stapp. He was the definitive expert on deceleration. He survived a 46g decel, although it was not... uh... "comfy". He was also a family friend; my dad bought my first train set from Dr. Stapp as they were preparing for a transfer. Dr. Stapp, who was given to witty aphorisms, is possibly the "inventor" of Murphy's Law.

[GaryHinshaw]

Good grief, 46 g is a crash, not a "deceleration".  To put this in context, 46 g would stop a car travelling 60 mph in 0.057 sec, in which time it would travel a distance of 0.75 m.  This is about the distance a passenger in a car would travel if the front of their car hit a concrete wall and it started to crumple.  So he survived the equivalent of a 60 mph crash into a brick wall... 

[C855B]

Ah, yes... but Dr. Stapp's "collision" was from ~600 mph, so they must have been softer bricks.   While he was the supervising scientist on these experiments, he felt personally responsible for the extreme tests and would not subject test pilots/victims to the abuse, putting himself in the seat. My folks were amazed each time he survived these outings, albeit with lots of internal injuries. For that matter, passing at a ripe old 89, he outlived my father, by quite a bit.

[Iain]

Already been tried; 130 or so years ago in NYC.  Wound up being abandoned due to being too costly to operate.