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Comment by Gustomaximus | Hacker News Reader

When they ask 'why has it not been this way" isn't the obvious answer 1) Infrastructure cost. Building this vs tracks on the ground would be a significantly higher investment. And 2) if something goes wrong with the engine, the entire line is shut down, vs pushing a train off the track and other trains continuing.

And I missing something but aside form the gradient capability I didn't see much advantage presented here. And if you are going to build these atmospheric pipes why not put the carriages inside them? I wonder if you could combine the 2. Have express trains shooting through the pipes and local/scenic trains riding that energy on-top. Workable or not, great to see people developing ideas!

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> if you are going to build these atmospheric pipes why not put the carriages inside them

Because when the vacuum breaks then people die if they are inside. This happens to be one of the biggest weaknesses of Hyperloop. It's not a good system when a failure _anywhere_ in the pipes causes a massive loss of life. If this guy's propulsion fails then, well, the train stops gradually, not a biggie. If air enters into a vacuum tube where the Hyperloop carriage is, the shockwave will do something to the carriage people ride in and it won't be pretty.

Really? How? Couldn't the train stop if the pressure starts to go up too high? It sounds a bit like saying, a broken rail _anywhere_ in a train network causes a derailment and massive loss of life. Train drivers can't see broken tracks until it's too late to stop.

1. Pressure.

2. Speed. 1600 km/s is pretty snappy.

Thunderf00t tends to wibble on a bit and repeat repeat himself, but he does make his point.

Relevant bits start about 6m22s.

https://m.youtube.com/watch?v=Z48pSwiDLIM

Or at 10m28s in this video:

https://m.youtube.com/watch?v=RNFesa01llk

I'm sorry isn't this the guy that has a creepy obsession with Anita Sarkessian and that associates with ~Nazis~ anti-semitic misogynistic racists.

He definitely has commented on Sarkeesian, and critiques some elements of feminism, a few of whom richly deserve it. That's not an area I'm particularly interested in, and I've not followed his videos there.

His critiques of poorly-conceived technological concepts, in particular the "Solar Freakin' Roadways" scam, and Hyperloop, strike me as largely on-mark (if repetitious and self-rightous).

I'm not familiar with any Nazi or other associations, though that would be most unfortunate.

RationalWiki addresses some of this:

http://rationalwiki.org/wiki/Thunderf00t

It has no bearing on the technical criticisms addressed above, however.

His comments on Anita Sarkeesian are creepy and obsessive. Let alone the fact he blatantly and deceptively edits her videos to make his point. https://www.youtube.com/watch?v=7bVqfQvXP2o .

If he's dishonest (not that he's wrong, but that he's dishonest) about basic social studies why should I trust his science? Let alone his experimental results? To be fair he recently disassociated himself from the alt-right ("not") nazis. So there is that at least.

> 2. Speed. 1600 km/s is pretty snappy

Way too snappy. Surely you meant /h not /s

Wups, yes. My error.

>If air enters into a vacuum tube where the Hyperloop carriage is, the shockwave will do something to the carriage people ride in

This is Thunderf00t's "shock wave" argument, and it has survived frequent debunkings. Are we really so easily misled that slapping sciencey branding behind any poorly thought out claim will cause people to repeat it as truth?

The huge thing he forgot is... pipes are not lossless! A tube break would initially cause the air to rush in at the speed of sound, but after a few kilometers the backpressure from friction with the tube walls will slow the air to highway speed and spread out the pressure rise. The way it works out, if you're close enough to the breach to be killed by the pressure wave, you're close enough that you can't stop in time before derailing.

> The way it works out, if you're close enough to the breach to be killed by the pressure wave, you're close enough that you can't stop in time before derailing.

Huh? Who's derailing here? The problem is, again, that if just a seal breaks close enough to a carriage, you are dead. This is not comparable to a derailing which requires quite a bit of things go wrong on a normal train or the propulsion dying in this elderly chap's magnetic train.

I think he meant in comparison to a train track breaking up with a high-speed train on it. Read the sentence more carefully as a comparison against existing train technology.

> ...if something goes wrong with the engine, the entire line is shut down, vs pushing a train off the track and other trains continuing.

The train is propelled by being magnetically coupled to a shuttle running underneath it. You could have more than one such shuttle; and the shuttles wouldn't have to run the whole length of the trip (potentially hundreds of kilometers in Germany, for example). There could be a new engine every few kilometers, with a backup. These engine units would be easy to replace; even easier than trying push a train off the track (which is not easy).

> ...if you are going to build these atmospheric pipes why not put the carriages inside them?

The pipe has to be much bigger to do that, and the pipe has to have an airlock to let people in and out of the train car. The airlock especially is apt to be a source of maintenance problems and safety incidents.

There are certainly operational issues around centralized power vs decentralized engines attached to the train itself. If successful, the additional construction cost could easily balance the fuel cost of moving engines around with each train, and maybe additional maintenance required for a moving engine vs a stationary engine. It's probably worth comparing to electrified rail service, which shares the benefit of not shipping fuel with passengers.

In addition to all the safety constraints mentioned, it's just simpler to build a 12-inch diameter vacuum pipe than a 12-foot diameter pipe. It might be possible to constrain the rolling stock on a line so it all clears the pipe, with some trains propelled by the vacuum pipe, and others propelled by an attached locomotive (such as maintenance vehicles, or conventional trains when the vacuum system is under maintenance, etc)

Isn't the initial track-laying cost the #1 obstacle to rail transport? IIRC it takes decades at least to break even with normal profits. I can't see any new train technology being successful unless it either fixes that problem or does something really impressive (e.g. supersonic speeds a la Hyperloop).

Decades to break even means like 5% ROI. Given how nobody seems to know where to stuff money these days (especially pension funds), the main concern is increasing the probability of success (i.e. make the risk profile match the returns).

> pushing a train off the track

How do you mean? You can push failed trains along the track with another locomotive, or you can crane them off (if you can get a crane nearby!), but you can't just push them to the side?

In my experience single line routes that terminate always have short passing lanes (terminology?) so that trains heading in opposite directions can get passed each other.

You'd only need to move the disabled carriage / section to one of those to enable at least some capacity for the line to continue operating.

That was my interpretation of the comment.

. . . short passing lanes (terminology?) . . .

I believe "siding" is the word you are looking for.

Its worth pointing out that for aerodynamic reasons it might take over 10000 HP to push a train at 300 MPH but if you just want to get it out of the way a farm tractor could easily push a train at perhaps 10 MPH. Even if you only go up a hill at 2 MPH its still faster than sitting there.

There's no physical connection with the piston in the pipe, just a big magnetic field. Without air pressure differential to make an air-bearing the friction between the magnet and the pipe wall might make it impossible to drag the train along. In a way, having a built in emergency brake might not be that much of a bug...

Another difference between humans and bulk cargo WRT transport systems is humans will self unload and self load into slower and less ecological and less efficient more expensive transport when and if necessary. Surely in the event of a breakdown a fleet of smokey diesel charter buses and taxis would appear to transport the people. On the other hand, the railroad has a real problem if a thousand tons of coal cars breaks down in the middle of a route, that coal isn't going to walk itself into an adjacent pickup truck or something.

> There's no physical connection with the piston in the pipe, just a big magnetic field. Without air pressure differential to make an air-bearing the friction between the magnet and the pipe wall might make it impossible to drag the train along. In a way, having a built in emergency brake might not be that much of a bug...

I'm not sure I follow. There has to be some way to start moving from a dead stop, so the plug will probably already have some kind of wheels or bearings to allow it to get moving until there's enough velocity to make the air-bearing work.

> I missing something but aside form the gradient capability I didn't see much advantage presented here.

* You can re-use existing carriages without having to seal them hermetically.

* You don't have to build a sealed tube for humans: No emergency exits every mile or so, no airlocks at stations except for maintenance access.

* Because the system seems to be just as wide as the tracks, existing tracks could step-by-step be retrofitted.

* Give the construction crew a few extra bucks to put some fibres in there ;)

> * Give the construction crew a few extra bucks to put some fibres in there ;)

I don't you want your fibre getting smashed by magnets all day :P

How is an _optical fiber_ affected by _magnets_ ?

When it gets crushed by the passing bolts of magnets which consume the entire tube diameter because they are propelled by air and need to fill the entire tube in order to work.

If you want to run fibre along, and it's a good idea while you're digging away, do it in a parallel but separate tube.

I think that was the idea of the parent comment, just put anything else in the hole in the ground. Fiber is welcome :)

There is a lot of fiber running in railroad right of way.

Southern Pacific Railroad Internal Network Telecommunications, or SPRINT. The telecommunications name survives. The railroad is now part of Union Pacific.

I suspect that the folks putting fiber in railroad right of way know how to avoid crushing failure.

> Give the construction crew a few extra bucks to put some fibres in there ;)

Isn't that what has already been done (at least in North America?) Weren't most fiber lines run in existing railway right-of-ways?

The article doesn't do a great job of actually explaining how the system works. If it's just this high pressure pipe with a carriage in it, then wouldn't you be able to retrofit existing rail lines? Regardless, another advantage is the centralization of the energy source.

Since the train has no motors, a lot of weight can be saved.

Reduced noise was another advantage as well as potential for powering with solar.

Good point about it breaking down.

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