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I still don't understand why there is any interest in this concept, either for freight or passenger transport, over a regular train.
by fredley 5y ago
I still don't understand why there is any interest in this concept, either for freight or passenger transport, over a regular train.
- IshKebab 5y agoElon Musk
- sneak 5y agoVastly higher speeds is the reason it would be valuable if it can be made economically feasible.
- TillE 5y agoIt'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.
- tsimionescu 5y agoIt 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).
- bluGill 5y agoWe can do it in the ISS. Not an easy problem, but it is a solvable problem. The problem is all the solutions will cost a ton of money.
- avianlyric 5y agoThe 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.
- bluGill 5y agoThe outside is a vacuum, the inside is at pressure. While the forces are reversed, the problem is otherwise the same.
- tsimionescu 5y agoThe 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.
- Ekaros 5y agoI 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...
- panick21_ 5y agoThe original Hyperloop system is designed to not require a vacuum as strong as other vacuum systems of the past. https://www.tesla.com/sites/default/files/blog_images/hyperloop-alpha.pdf https://www.tesla.com/sites/default/files/blog_images/hyperl... > 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.
- tsimionescu 5y agoWell, 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.
- panick21_ 5y agoI 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.
- wyldfire 5y agoHow long does it make sense to investigate that question?
- anchpop 5y agoPractically 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.
- mimsee 5y agoI 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.
- fredley 5y agoDoes 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?
- bluGill 5y agoSome 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.
- ramphastidae 5y agoBecause the current passenger rail “system” in the US is horrendous.
- moffkalast 5y agoSo.. maglev?
- bluGill 5y agoNot really helpful. It can go slightly faster, but wind resistance is a problem you can't get around.
- trhway 5y agoYou 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.
- bluGill 5y agoNobody has tested maglev at 700km/h. https://en.wikipedia.org/wiki/Railway_speed_record 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)
- trhway 5y ago>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/File:TGV_World_Speed_Record_574_km_per_hour.jpg 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.
- hammock 5y agoWhy do articles about fusion power keep hitting HN over regular nuclear power?
- goldenkey 5y agoFusion 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.
- hammock 5y agoAnd hyperloop has the potential to replace millions of gas-burning cars, buses, trains and planes...
- goldenkey 5y agoIt still has to be powered..so the gas-burning thing is a bit disingenuous.
- tsimionescu 5y agoHow? 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.
- tsimionescu 5y agoNo, 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).
- c7DJTLrn 5y agoInnovation is dead and its rotting corpse is used to scam foolish investors.
- bluGill 5y agoBecause 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.