4000 mph Mag Lev Train, is it possible?

[boogabooga]

http://news.yahoo.com/blogs/this-co...riting-rules-high-speed-travel-153438350.html

 

[TMac3000]

Sounds great if you don't mind communting at 5 Gs:shifty:

A suborbital airliner would make for sense: anywhere on the planet in less than 3 hours

 

[Urwumpe]

Sure possible, but the faster you travel, the more energy the mag lev consumes. Currently, you have a good break-even between speed and costs at 450 km/h, but more would be possible. But not as commuter train, that isn't the best for mag levs. Long distance travel is better there.

 

[boogabooga]

They say in the video that they are limiting acceleration to 1G.

Imagine, though, if the outer tube chamber ruptures and it pressurizes.

 

[garyw]

I'd hate to be on that thing when the emergency brakes come on. I commute on the UK's HS1 - 140mph on bits of track and we had an emergency stop the other day. 140MPH to zero in about 10 seconds results in a very firm stop at the end.

 

[TMac3000]

They say in the video that they are limiting acceleration to 1G.

Imagine, though, if the outer tube chamber ruptures and it pressurizes.

Happy drowning!:tiphat:

---------- Post added at 04:43 PM ---------- Previous post was at 04:42 PM ----------

Oh, wait, you would be goo before you could drown...

 

[Pipcard]

In fact, there was a documentary about a Transatlantic Tunnel on the Discovery Channel.

(an episode of "Extreme Engineering"; that show had some epic visionary stuff in the first few episodes, then it turned into more mundane things)

 

[Zatnikitelman]

The idea is actually good, but massively expensive. By my calculations, it would take 183.3 seconds to decelerate at 1g from 4000mph to 0mph. That's a lot, but for just about any problem, your train would be past it long before it became a problem, or the computer could detect the problem and slow the train when it's farther out than the 3 minutes it takes to come to a stop.
Energy isn't too much of a concern actually, yes, it'd require a lot of energy, but a lot of that can be regained through regenerative braking just like hybrid cars and electrified railroads do today.
I hesitate to just throw good ideas like this out onto the internet, but given some of the impracticalities, I don't mind about this one: What would be interesting to do is build a few "cargo" maglevs as roll-on roll-off for rail vehicles so maybe an Acela rolls onto the train in New York from Washington D.C., then rolls off in Plymouth to St. Pancras in London giving people a one-seat ride from Washington D.C. to London, England.

 

[Jarvitä]

Well, that's the first time I've seen "vacuum" and "constant acceleration transfer" associated with trains.

I wonder what kind of energy expenditure would be required to even maintain a few thousand kilometres of tube in a vacuum in the first place. And how easy it would be to poke a hole somewhere along it, disabling the entire maglev network...

 

[PrestonJames]

I think keeping the tube evacuated would be a small problem compared to actually engineering the track. The clearances for maglev tracks are already a challenge for engineers. Imagine the force necessary to keep the train levitating on even the slightest curve or incline at those speeds...

 

[MattBaker]

I thought about the accleration from 0-1800 m/s with 1g:uhh:

The time to acclerate is 183,5 seconds, with an uniform accleration you end up with s = 0,5 * 1800 m/s * 183,5 s = 165,150 m or 165.150 kilometer (100 statue miles)
So, you could build a railway (tunnel) from London to Paris and you would constantly acclerate or brake, sounds cool.

And 165 kilometers to brake? "Sir, we have a local farmer parking his tractor on the railway!" - "Where?" - "100 kilometers from here!" - "Bloody hell!"

So, 4000 mph sounds nice, but not with 9,81 m/s².

 

[n72.75]

"Eyeballs in" the human body can sustain up to 6 gees comfortably.

 

[Linguofreak]

And 165 kilometers to brake? "Sir, we have a local farmer parking his tractor on the railway!" - "Where?" - "100 kilometers from here!" - "Bloody hell!"

Except that he's not going to be parking his tractor on the tracks because the tracks are in a sealed, airless tunnel. (And the tunnel is sealed and airless because you're traveling fast enough that you don't even want air getting in the way, let alone a tractor). It's even a good bet that the tunnel is underground.

 

[Thunder Chicken]

I think keeping the tube evacuated would be a small problem compared to actually engineering the track. The clearances for maglev tracks are already a challenge for engineers. Imagine the force necessary to keep the train levitating on even the slightest curve or incline at those speeds...

Actually has nothing to do with your quote except you mentioned forces: FYI-You get a bit of centrifugal "lift" at those speeds, something like 1.6 ft/s^2 or about 0.5 m/s^2.

Agreed that typical turn radii of normal tracks would require massive accelerations to hold on to the train. Maybe only "great-circle" routes will be allowed?

 

[ADSWNJ]

So 0-60 mph in 5 secs is a pretty decent acceleration (e.g. Dodge Viper, Subaru Impreza). 60mph is 26 m/s, so 0-60 in 5 secs = roughly 0.5g push into the seat. Doing it in 10 secs (at 0.25g) is more like a typical car (eg. Honda Accord), so nothing special.

If the train went to 2000 mph (900 m/s) at 0.25g, it's about 6 mins. (Let's face it - even 2000 mph would be an amazing feat, and you would be traveling at a faster ground speed that Concorde ever went, for example.) That leaves some contingency for a sharper deceleration.

Recalling the Discovery episode, I think they had the concept of safety cells with airlocks, so the risk of a rupture would be limited to a sector. The San Fran BART shows that the concept of a tube in open water is accepted by the public (though admittedly at a much shallower depth and for less travel time). I think the idea of doing it for cargo first would make a lot of sense.

As for keeping it on track (literally) - I assume you would energize a short sector alongside the train, and you could do the same with side-rails to control the cornering.

Bring it on!!

 

[dumbo2007]

Yeah I was also wondering if the train could be at the center of the tube from all directions(even the bottom), say a gap of 4 or 5 meters in the high speed regions. The the chances of colliding with the walls is reduced for minor speed variations. The gap could increase with the speed of the the train moving it towards the center of the tube. Then moving it closer to the bottom, where the tracks, are for slower speeds.

So the train would be in a magnetic tunnel inside the physical tunnel, with the strength of the field varying in proportion to the speed. Any deviation towards the walls causes a surge in magnetic force, pushing the train towards the center of the tunnel.

 

[Richy]

Sounds a bit like SwissMetro, that was also Quite Popular some years ago.
As far as I remember, the biggest problem is to evacuate such a huge volume. Imagen a tunnel with 2m diameter, an e.g. 10'000km lenght.

 

[Loru]

"Eyeballs in" the human body can sustain up to 6 gees comfortably.

I wouldn't call 6G comfortably. I experienced 30 secs positive 3Gs and it was terrible. Also take a note that it's a train not fighter aircraft.

I can't imagine regular passengers feeling comfortable in this kind of transport.

 

[APDAF]

I watched that episode and they had rotating seat I can recall.

 

[Zatnikitelman]

Yeah I was also wondering if the train could be at the center of the tube from all directions(even the bottom), say a gap of 4 or 5 meters in the high speed regions. The the chances of colliding with the walls is reduced for minor speed variations. The gap could increase with the speed of the the train moving it towards the center of the tube. Then moving it closer to the bottom, where the tracks, are for slower speeds.

So the train would be in a magnetic tunnel inside the physical tunnel, with the strength of the field varying in proportion to the speed. Any deviation towards the walls causes a surge in magnetic force, pushing the train towards the center of the tunnel.

Conventional maglev technology is more than sufficient to handle the spacings required and high speeds required, fancy "magnetic tunnels" just aren't needed.