HN Theater @HNTheaterMonth

this for example https://www.youtube.com/watch?v=p9Ig19gYP9o

A decade ago, there was a Chinese proposal for a non-stop bullet train: https://www.youtube.com/watch?v=p9Ig19gYP9o

I don't think anything came out of that, but it's a cute idea, especially for high-speed stuff.

There is also this Chinese concept train that never stops at a station: https://www.youtube.com/watch?v=p9Ig19gYP9o

⬐ jimmcslim

And a European concept that is similar:

https://vimeo.com/25403519

Side-by-side instead of on-top. The Chinese concept has the benefit of using less space. I don't know if either could be engineered to be practical or safe.

At any rate, the most important question is... Did you NUGGET your boots this morning?

⬐ chrischen

European one seems really over-engineered.

⬐ Someone

Practical or safe? Probably. Practical and safe? I doubt it. On a standard railway platform, leaving late because some passengers hold up the train is a nuisance. With systems such as these, it is lethal.

For the EU one, the critical timing is in detaching from the fast train. It _has_ to happen before the two tracks split up.

For the Chinese one, detaching can be postponed indefinitely, if slow cars in front know it soon enough, and can pull up fast enough. I think that makes this system slightly safer. Worst-case, an emergency command 'all trains to full speed' will 'just' move most passengers to stations a few hundred miles from where they wanted to go.

In either case, I would expect that, to guarantee proper timing of detachment, the doors between fast and slow trains would have to close at least a minute, probably more, before separation. For the EU design, that means long side-by-side tracks. For the Chinese one, it limits the distance between stops of the docking train. One could solve that by allowing two slower trains to dock at the same time, but that increases the risk of collisions tremendously (two half-width trains docking side by side might be the best solution here)

There must a transport revolution going on in China. It instantly reminded me of this video:

http://www.youtube.com/watch?v=p9Ig19gYP9o

These trains that never stop seem a lot more feasible than the buses. Granted it would require a massive amount of work from an infrastructure perspective but it seems like such a brilliant solution that would make public transport infinitely more appealing.

⬐ blahedo

This is reminiscent of the way the old-fashioned cablecars worked (and still work in San Francisco): the cable snakes through the system and is operating at full speed always, while the cars start and stop by slowly releasing or catching the cable.

⬐ natep

This was posted to HN before. The comments on that were basically, it's been done before, and wasn't economical/safe. Keep in mind, you still have to spend energy to accelerate the cars, and there are a lot of safety issues introduced by the extra complexity.

⬐ asimjalis

Implementing the idea and making it work safely would be quite innovative. I can see a lot of things going wrong.

* What if the door on the pick-up car gets blocked? Sometimes straggling passengers hold the door open for their friends. It would need to get out of the way to prevent a collision with the drop-off car.

* What if there is a malfunction in the pick-up car so that it is not able to accelerate fast enough to catch up with the train?

* From an engineering point of view this seems fragile -- there are a lot of parts that need to perfectly synchronize with each other. A single error will quickly cascade through the system and result in serious loss of life.

⬐ hxa7241

Yes, and weighing the whole thing against alternatives makes it questionable.

First, it might save lots of energy, but it is also a lot more complicated than just having brakes, which it is going to have anyway.

And how much energy would it really save? It still has to accelerate that detachable portion which could be a substantial fraction of the whole, and furthermore the train would probably need to be substantially heavier to support the extra mechanism, which would be a loss . . .

Still, it is a creative leap, which makes one think about how to be similarly inventive. You have to get some wild ideas before figuring out the details.

⬐ KiwiNige

>> but it is also a lot more complicated than just having brakes

At least one train maker still struggles getting this bit right. http://en.wikipedia.org/wiki/Siemens_%28train%29#Braking_iss...

I'd be very worried about safety with something this complex unless it could be proven to always fail in a safe way.

⬐ RiderOfGiraffes

It saves a lot of energy. Accelerating one part can be done by taking energy from the incoming sub/super carriage. Accelerating and decellerating the smaller carriages is much more efficient than the whole train.

⬐ krschultz

Are you sure? How much extra air drag will there be having a hump that basically doubles the frontal area and adds a load of form drag?

⬐ lftl

I'm less worried about energy, and more about time. Not having to stop at every stop along a route would cut a lot of commute time, and make adding more stops more feasible.

⬐ hugh3

How's this for a simpler implementation without many of the problems which have been mentioned:

Approaching the station, there's an announcement on the train "Everybody getting off at the next station please move to the last carriage". Then the last carriage simply detaches from the train and coasts into the station to unload at the platform.

Meanwhile, another carriage has been loaded with the passengers who were due to get on at the station. After the train passes the carriage is shunted by a small locomotive to catch up with the train and it attaches to the end.

No need for crazy long parallel tracks and dangerous transfers between high-speed trains. Difficulty: most high-speed trains have locomotives at both ends afaik, but that's a minor issue.

⬐ DTrejo

If this is a high speed train, and the front car of the train is always being rotated backward, how do you deal with making sure that this first car is aerodynamic, and remains aerodynamic once it is no longer the first car?

⬐ hugh3

That wasn't what I was suggesting; I'm suggesting changing the back car. The first (N-1) cars remain the same throughout the journey and the rearmost one gets swapped at every station.

⬐ thingie

High speed trains don't have any locomotives (only German ICE1 uses this approach), powered axles (and other electric equipment) are distributed across the whole unit. (So you can't split it, only couple/uncouple two units together.)

But, if you think that those transfers are dangerous, I don't know what to say about coupling in high speeds. Insane, maybe :-) Coupling even in station when only the locomotive is moving is favorite source of accidents. Basically you'd have to reach almost same speed as the train you are coupling with in the exactly same moment when you are going to touch it, with only very small difference that buffers can absorb. Hard enough if that speed is zero.

⬐ extension

Surely the trains would be specially constructed to perform this procedure reliably, and it would be entirely automated. This doesn't seem like it should be a hard problem if the system is engineered from the beginning to handle it.

⬐ thingie

Coupling two things together in 200 or 300 kph is not a hard problem? That's like people without any programming experience saying, hey, that traveling salesman can be easily solved for 10 nodes, so just add more power and solve it for 100 or 1000, that cannot be that hard!

It's quite hard to control exact speed of a train (at such high speed), even without any atmospheric effects and with ideal adhesion conditions that never change. I can imagine it in like 50 kph, when the worst thing to expect is a derailment, some deformation zones blasted, and few non-fatal wounds. But every problem rises at least exponentially with the speed.

⬐ None

None

⬐ extension

Ok, it's a hard problem, but there's gotta be a way.

Maybe the coupling mechanism could be something long that extends from the back of the train. The cars can connect can over a wide range of distance, kind of like a runway. The connection is made with a friction clutch that can be applied gradually and eased off if something goes wrong. The coupling also has a drive to pull the cars together after they are securely linked.

They could always slow down to make the link too.

⬐ None

None

⬐ thingie

And still. Does anyone except military use in-flight refueling? Is every attempt of in-flight refueling successful? If you suddenly lose some speed or something (unfriendly wind or whatever), you have plenty of space to maneuver, and even in the worst case, you should have rather good chance to survive hit by that pipe.

ICE train in Germany got derailed by few sheep two years ago…

⬐ hugh3

Fair enough, I hadn't realised how difficult it was to control the exact speed of a train at high speed.

But if that's the case then it still seems like the original problem of running two trains right alongside each other, on different tracks, for several minutes while people cross from one to another, and with the consequence of any error being passengers getting sliced in half, would be even harder.

⬐ hussong

Version with explanation in English: http://www.youtube.com/watch?v=K27VmNfwsaQ

⬐ JulianMorrison

Hah, I invented something like this in my head for amusement, except mine used swappable modular carriage pods that plugged into the train from the side, and a steam catapult for high-gee synchronization and emplacement. I can't see a sensible use for it though.

⬐ nooneelse

I just figured that half the kids watching Knight Rider back in the day thought of a similar trick using cars and trains... I know it was a day dream of mine for a while.

⬐ mmt

Nowadays, I'd be delighted to do this trick with the train being stationary, especially for an intercity route.

It would eliminate the hassles of car rental (especially if the rail stations aren't near airports), obviate the need for checked luggage, and mitigate the increased travel time compared to flying.

⬐ JulianMorrison

It would certainly help if the car in question was robot-controlled and could jump several meters vertically without a ramp.

⬐ _delirium

Here's a brief post about this video from a few years ago: http://www.goodcleantech.com/2008/07/futuristic_train_lets_p...

⬐ hussong

I'm still wondering what the docking looks like. Somehow people need to get from the connector cabin to the train and back. This could also result in a lot of people moving back and forth within the train over 20 stops if you can only get in and out at the back of it.

⬐ archenemy

maybe the connector cabin could move along the train and dock above every car. my main concerns are existing tunnels and the aerodynamic profile.

⬐ andrewtj

The route mentioned in the video has 30 stops over a distance of ~2200 km so it's unlikely there'd be much congestion. Stops here in Australia are even sparser over those sorts of distances so it'd work quite well here too.

⬐ vaksel

pretty cool...kinda sad that the U.S. stopped doing cool things like this. What was the last big infrastructure project?

⬐ hugh3

Remember that big infrastructure projects are a lot easier in China since the government has no hesitation about demolishing entire villages which might sit in the way of the latest highway, rail line or dam.

⬐ rbranson

O? http://en.wikipedia.org/wiki/File:Chongqing_yangjiaping_2007...

⬐ nanotone

That's an extreme example. How many people are going to fight to keep their home after having power and water cut and a 30-foot pit dug around it?

Keep in mind that on the whole, Chinese people are much more likely to give up personal property/liberty for the benefit of the state. It's a massive generalization of course, but the difference between Chinese and American mindsets is really significant.

⬐ steveplace

Our infrastructure projects assume that oil is going to stay at 80/bbl.

⬐ pierrefar

Looks cool as a concept but I'd like to see an actual implementation.

Also, the initial jolt on impact of the pick-up car is going to be very unpleasant, and perhaps even dangerous.

⬐ thingie

Hardly an innovation. Various people already had the same idea so many times. It seems quite an obvious and tempting thing to do.

http://blog.modernmechanix.com/2008/12/18/train-picks-up-and...

Well. It's pretty much unworkable. Train is not a single rigid body, it's composed from bogies and car bodies, and they are only quite loosely attached. They absolutely have to be. So you can't expect it to just sit as a rock on the tracks, even in pretty low speeds. And with speed low enough, you are maybe better to simply stop. Modern electric bullet train unit with high powered axles ratio can accelerate really, really fast.

Anyway, you could spend money much better on allowing higher speeds on the whole track, or improving adjacent tracks so to allow higher speeds even for feeders and conventional trains, which could allow you to make fewer stops.

⬐ _delirium

The comments on that link point to an interesting poor man's variant (disembarkation only): http://en.wikipedia.org/wiki/Slip_coach

Pretty obvious I suppose, but interesting that it was actually used in routine service for a few decades.

⬐ narag

I've thought inmediately of Asimov's The Caves of Steel where pedestrians jump from a moving band to another, some slow, some faster.

For trains it could be nice to use small wagons that could change from a train to another, not because of energy saving, but to achieve more speed, avoiding the time needed to change lines. I agree with a previous commenter that trusting passengers to behave correctly is looking for problems.

⬐ stcredzero

Modern electric bullet train unit with high powered axles ratio can accelerate really, really fast.

Yes, but accelerating the entire train is going to cost way more energy than accelerating the transfer car. Also, the transfer car can simply use wheels and brakes to gain kinetic energy from the train, so it can be incredibly light. Even if a longer track and motor are necessary for high speed bullet trains, there would still be a big energy savings.

Also, no matter how quickly you can accelerate to make a stop quickly, the same train will be able to save considerable trip time with the transfer car system. Saving a half hour or hour off of trip time from a route is certainly worthwhile, especially if it means that the train can run the same route at a lower top speed. The energy savings from that could be enormous over the long term.

⬐ thingie

Well, even just weight of the people in the transfer car will make it quite heavy (few tons at least). And you are not going to make this for just 10 people at each (non)stop.

You could save some energy by using only recuperating electrodynamic brake to zero to stop the train and store it in some supercapacitators (not on the train, of course) if there isn't any other train to use it. Because you have many powered axles, you could brake quite effectively and fast enough. Well, possibly still not fast enough to use just EDB.

Raising top speed is of course going to cause much higher aerodynamic drag, so if the energy use is primary concern, it's not exactly the right thing to do. I rather meant eliminating any drops in the average traveling speed except the stations.

But I can't really argue against energy savings, because most likely, there would be energy savings :-) If you could built such a system safe enough (I don't believe that) and with less than absolutely insane costs (I don't believe that either :-)).

⬐ wheels

I'd also thought of this independently in the past, presumably lots of people have. As for decelerating, I have no idea if any modern trains do this, but you could in theory charge a battery with the kinetic energy from decelerating the train and use that for acceleration. Naturally it wouldn't be a perfect energy transfer, but I presume much of it could be captured.

⬐ quant18

http://en.wikipedia.org/wiki/Regenerative_brake

Seems like it's everywhere these days. Even in urban metro lines where you've got like 1km between stations. HK subway trains have been doing this since the 90s. Wikipedia sez Delhi Metro has it too.

⬐ thingie

It's most useful in such cases (and trams and so on), with very frequent braking and starts and a lot of trains. There is always some other train accelerating. And you have majority (if not all) axles powered, so you can have regenerative brake on all of them, allowing you to brake effectively only with the regenerative brake to almost zero. It's even much more silent than a mechanical brake, also an advantage in urban environment :-)

(And even if you don't give the energy back to the network and just burn it in the resistors in locomotive, it gives you more effective braking. Locomotives from 1960's already had that.)

⬐ thingie

It's quite common. Except that there are no batteries (battery won't do, you can't charge it fast enough), you just need to have another train in the same section to consume it (or whole network, if your converter substations are ready for that). Energy savings estimates were like 10 to 20 percent (don't have any link for this, it was some British study I remember, sorry).