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Comment by ramphastidae | Hacker News Reader

Because the current passenger rail “system” in the US is horrendous.

I don't think you're necessarily wrong, but how does putting a train in a vacuum tube solve the problems we currently have with passenger rail?

The limit on speed is air resistance.

That would be true if US passenger rail was actually capable of high speeds to start with.

As it stands right now US passenger rail is total joke compared to the rest of the developed world. Slower, less reliable, more expensive. Air resistance in the US is the same as everywhere else, so that isn’t the limit factor.

True, but hyperloop isn't needed to solve any of that.

That is just one of the limits. At the speeds hyperloop was proposed to go, you need really wide curves to limit g-forces on the passengers. Not just when going left or right, but also up and down. It would be an absolute nightmare to get all the right-of-way done, and even then you would need immense amounts of earthworks to start curving uphill miles before the hill actually starts.

Let's walk before we run. Getting Shinkasen-style trains in the USA should be step 1.

I agree. Lets stop trying to innovate trains. The laws of physics make it clear there isn't much left to do for speed. Any innovation left would be around construction (and even there the world is doing well, most innovation really needs mass production)

The limitations are financial (both building the tracks and acquiring at some new right of ways) and geographical (a lot of distances in the US are quite big and most people won't take a train if it's a lot slower than flying).

So.. maglev?

Not really helpful. It can go slightly faster, but wind resistance is a problem you can't get around.

You can plasma sheaf the train head. The stability of wheels/rails and other mechanical stuff at say 700km/hour is probably a bigger issue than air resistance.

Nobody has tested maglev at 700km/h. https://en.wikipedia.org/wiki/Railway_speed_record The conventional train speed record is only 30km/h slower than maglev. The issue with the conventional train wasn't wheels it was the overhead wire contact (though at that speed maglev is more efficient)

>The conventional train speed record is only 30km/h slower than maglev

there is a reason that train is so short https://en.wikipedia.org/wiki/Railway_speed_record#/media/Fi... - in the wheeled train the vibrational modes induced at those speeds and the resulting forces will tear the train apart.

>the overhead wire contact

well, batteries on the train would solve that. That one thing in HyperLoop Musk got right.

> well, batteries on the train would solve that. That one thing in HyperLoop Musk got right.

Batteries will never have the energy density to solve that. Just basic physics. Even diesel fuel isn't really good enough

None of the reasons that the current passenger rail system in the US is horrendous are technical. It's entirely feasible to build proper passenger rail networks with current, look at Japan and western Europe for some examples. The problems are all sociological in nature.

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