I saw a thing on TV and few years back on how the hyperloop was going to change the way people got around. It seemed very implausible to me and I haven’t heard anything about it since. My questions are 1; was this a real thing and 2; what is the latest news on it.
There was a proof of concept test run done about nine months ago. Supposedly the tunnel Elon Musk is building right now to get to the airport in Los Angeles is being built with Hyperloop in mind. Whether it all pans out remains to be seen but it is not forgotten.
The theory of the thing is fine. No particular reason it can’t work. It just seems to me it is waaay too susceptible to attack. A vacuum tube running across the state? Seems to me one joker with a pistol could poke a hole in it and then it will tear itself apart as air rushes in to fill the vacuum.
Or an earthquake or some other sort of a natural disaster and everyone in it is dead. I have problems believing the government would allow such a thing.
Don’t expect to ride on a hyperloop pod anytime soon but the idea is real and in development. Elon Musk has already built a test tunnel and has gotten teams of engineers to have speed competitions in it. He is also trying to invent a boring machine that is 5 - 10x faster than anything that already exists. The basic idea works in theory. There is no cutting edge physics involved but the logistical challenges to build very long tunnels at a reasonable price are immense.
Yeah, like in 1989 when 42 people were killed during the Loma Prieta earthquake as the upper deck of the Nimitz freeway collapsed. They ran right out and closed all the freeways. No, wait, they did that other thing. They left them open, because people have to get around.
A very small earthquake probably won’t do anything to a freeway, but that same earthquake could kill everyone in the hyperloop.
They are working on a project in Dubai:
Well, Elon Musk isn’t in the business of vaporware. He’s a member of the president’s business council.
There was a huge thread back when this idea first popped up, in which many of us looked at the practical issues relating to this. The thing about the hyperloop is that the idea isn’t new. It was floated at least a century ago. Elon Musk popularized it recently, but issues involved aren’t about whether it’s hypothetically possible (again, that’s been known for a long time), but whether it’s practical and cost-effective.
Did Elon get some kind of permission to be tunneling under L.A.?
As far as I know he only got permission to dig under his own property. Which makes what he’s doing even more puzzling.
Why do you believe it would kill everyone?
The tunnels he’s digging have nothing to do with hyperloop.
I’ll start believing the hyperloop companies are something more than a scam to attract investment money when I see any of them invest even half the time solving the serious engineering problems involved than they do preparing cool videos and designing futuristic pods and terminals that look good in investment brochures but which don’t address the serious engineering challenges of this thing.
The first place to start is metal expansion. Musk claims that hyperloop will be a solid welded steel tube, with expansion being taken up at the end terminals. This is a complete non-starter, because the tube isn’t straight. Therefore, metal expansion will cause the entire shape of the loop to change - by many hundreds of feet. and going straight isn’t even possible because the earth is curved and a straight line between two points is a great circle arc.
If you solve that problem, you can then consider buckling problems from differential heating on the top and bottom of the tube. And note we haven’t even talked about the challenges of maintaining a vaccuum, how you are supposed to get people out of the thing if a car stops in the middle, how you protect it and the people from catastrophic failure if the immense forces on it are released by a puncture, and on and on.
These are challenges with no current engineering solutions. So if you see a company claiming to be building a hyperloop but all they have to show you is lots of pretty models of termnal buildings and futuristic capsule designs, grab your wallet and run.
Because a hole in the tunnel lets air in, this re-pressurising would cause great turmoil in the vacuum tube.
The pressure difference between inside/outside the tunnel is greater than that between a plane and the atmosphere.
Train running at 500mph vs any turmoil is an accident waiting to happen.
This explanation doesn’t explain why the poster being asked the question thinks it will ‘kill everyone in the hyperloop’. This implies that the poster asserting this doesn’t understand that it won’t be one contiguous tunnel with a uniform vacuum throughout, or that engineers working on this would create a system that would kill literally everyone traveling in it if the tunnel depressurized. Which is kind of a silly thing to assert.
It would be like asserting that a loss in cabin pressure in your plane example would always kill everyone on board…which, you know, isn’t the case. Right?
ETA: Didn’t notice this was a revived thread.
Well, then, all he has to do is buy a strip of land 100 feet wide and the length of the proposed Hyper Loop, and he is in business! 
A loss in cabin pressure on an aircraft is nowhere near the catastrophic event of a train full of passengers moving at nearly the speed of sound suddenly hitting a wall of air. It would be about the same as slamming into concrete at the same speed. This isn’t about depressurization, it is about losing vacuum integrity.
Uh, no? Everyone thinks everything is a rubber balloon or soap bubble just waiting to burst. If there was a breach in the hyperloop, the trains would run less efficiently. Vacuums don’t explode and the tunnel is already under the pressure/weight of the atmosphere and structurally sound so it wouldn’t implode either. A breach would equalize the pressure (that is, reduce the net pressure on the walls). Why would this suddenly cause an explosion or implosion?
If the cabin, not the tunnel, were punctured odds are it would be a slow leak. Again, solid steel trains are not soap bubbles or rubber balloons, and the explosive decompression you see in movies resulting from, say, a stray bullet is… bad movie physics. Now, a high explosive bomb that blows open a huge swath of the train might do it… but derailing a normal train would have the same effect, and probably take less high explosives to achieve (blow the tracks).
Isn’t the temperature static once you get a few feet underground?
You’re discussing multiple small leaks from every direction. copperwindow was discussing a single, substantial rupture. In that case, you could end up with something like this:
