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.
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.
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).
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.
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)
Because airplanes are slow. In a vacuum (or in space!) you can go a lot faster without using a lot of energy. NYC to London in 2 hours including stops (Note that this assumes you cross from Alaska to Russia if you can cross the Atlantic instead it would be faster).
The expense is what kills it. The other problems are solvable with money, but there is no way getting around all the material needed to build it.
It can't be made feasible from an engineering POV, not just economically. It's virtually impossible to maintain a relevant vacuum in hundreds of kilometers of tunnel. The temperature stresses alone would cause leaks unless using some very special materials (if any exist).
> Another extreme is the approach, advocated by Rand and ET3, of drawing a
hard or near hard vacuum in the tube and then using an electromagnetic
suspension. The problem with this approach is that it is incredibly hard to
maintain a near vacuum in a room, let alone 700 miles (round trip) of large
tube with dozens of station gateways and thousands of pods entering and
exiting every day.
> All it takes is one leaky seal or a small crack somewhere in
the hundreds of miles of tube and the whole system stops working.
However, a low pressure (vs. almost no pressure) system set to a level where
standard commercial pumps could easily overcome an air leak and the
transport pods could handle variable air density would be inherently robust.
Unfortunately, this means that there is a non-trivial amount of air in the tube
and leads us straight into another problem.
Well, the best way to get very high speed rail is to abandon the pumps and tubes entirely and do it in open Air, e.g. Maglev. You won't see any significant energy efficiency gains until you get to pretty low pressures, and even then that will be entirely compensated by the effort of pumping out air if you can't maintain an excellent seal.
Basically, the only energy efficiency can come from the seals, since those essentially allow you to store the energy spent to move the air out of the way of the train ahead of time. Otherwise, whether you move the air by pushing the train through it, or move the air by pumping it out in front of the train, the total energy expenditure will be similar.
And again, the problem of maintaining even a somewhat low pressure in a hundreds of kilometers long above ground tube with no airlocks is well outside our current engineering capacity.
I have not done the math on the energy required to create the original low pressure and maintaining it compare to how much you save.
You speak pretty confidently about that, can you actually show any of that?
It also depends on how high the utilization of the tunnel is.
Who says there are no airlocks?
The proposal has been simulated by both SpaceX and Tesla, I don't think they made some basic mistakes about it being impossible to sustain a low pressure tube.
I suppose relatively bad vacuum is possible with enough energy expenditure that is pumps. What in my mind always made it stupid is throughput. First overall and then getting stuff in and out. Oh and safety... Minor thing being stuck in vacuum capsule middle of some hundred of kilometres long tube. I sure hope there is plenty of spare air...
The ISS isn’t kept at a vacuum and isn’t hundreds of kilometres long, and space needs no assistance from us to maintain a vacuum, gravity’s got that covered.
The ISS is not a tube hundreds of kilometers long, so I have no idea how this compares. Also, the ISS doesn't require pipes, and can easily have many segments which are airlocked from each other, which a high-speed train would not do well with.
I don’t think businesses care about speed but rather stability and throughput. If the vaccuum is broken how long does it take to get it fixed, the tube emptied of ”pods”, and so on.
It's a fine research project, but in terms of offering actual transportation services to people, there are a thousand more effective things to do to make high-speed rail services available, convenient, and economical.
High-speed rail is slower than a plane, sure, but it's way faster than a car.
Does freight need to go that quickly? Quicker than a normal high speed train? Is there enough value in the freight going faster to fund the infrastructure?
Some freight yes, some freight yes, probably not. Fruit and mail needs to go very fast and is often shipped by airplane. There are a few cases where regular shipping doesn't deliver on time and so an emergency order is air freighted in - at great expense.
I doubt that they can get their costs lower than airplanes. They need to buy land all the way from point A to point B, vs only at airports. Airplanes also run at a partial vacuum (30000 feet) by nature. As such it is hard to see anyone using them instead of something else. Where speed counts airplanes are faster, where speed doesn't count ships and slow trains in air are a cheaper.
Practically speaking, as long as they can convince people with control of capital (including the US gov't) that it's worth investigating.
The proper answer to your question requires information you're not going to get by asking HN, it's like asking how much time we should spend investigating fusion power. It completely depends on what leads people have, how promising the those leads look, how many "hard steps" are ahead of us, the benefit if we made it past them, etc.
Fusion has no waste products except ordinary elements, low on the periodic table. It's an entirely different beast. You could theoretically have a little Tony Stark reactor powering your home, safely.
No, that is entriely false. The main product of all currently plausible fusion reactors are neutrons. Those are extremely destructive to living tissue, requiring heavy shielding. Even worse, any material which absorbs neutrons becomes radioactive itself, so the shield inevitably becomes radioactive.
The advantage of fusion is that this radioactivity is short lived compared to uranium - decades instead of centuries or millennia. However, this also means that you have to stay much farther away from it, as it's much more radioactive than a piece of uranium which you can typically hold in your hand without any ill effects (just don't hold it under your pillow for a few years).
How? The initial plan was discussing something on the order of 850 passengers per hour between SF and LA. Fundamentally, such an expensive piece of infrastructure with critical safety concerns can't be a mass transit system.
