Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Hyperloop lays off half of its employees as it pivots away from passenger travel

businessinsider.com

Post reply on HN
Print view View original

121–130 of 155 posts

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#121

Post by tsimionescu »

bluGill wrote: post #60
tsimionescu wrote: post #23

Earlier quoted context omitted.

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).

We 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.

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.

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#122

Post by trhway »

bluGill wrote: post #116
trhway wrote: post #79

Earlier quoted context omitted.

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.

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#123

Post by tsimionescu »

kjksf wrote: post #83
tsimionescu wrote: post #9

Earlier quoted context omitted.

Boring company has abandoned any idea of a hyper loop a long time ago, right? Did they ever even associate with it (outside the branding of their Vegas mini tunnel)?

Yes and no. Yes, because they no longer plan to use the original design proposed by Musk (pods in vacuum in tubes installed on the ground). No because long term they still plan to do hyper loop but the latest iteration of the idea is electric cars driving really fast in under-pressurized underground tunnel. See https://www.boringcompany.com/hyperloop That being said, Boring Company is still in very early stages. They…

Well, the Vegas loop is just a short, expensive, small tunnel that took a very very long time to build (more than 1 year per mile) in a straight line with all permitting sorted out, so I'm not sure what it proves except incompetence.

Look at some Swiss alpine tunnels or the underwater Channel tunnel if you want to see advanced tunnel boring technology.

Edit: to give exact numbers: boring for LVCC Loop started on November 15 2019, and the tunnels opened to the public in April 2021, 1.5 years later for 1.7 miles (2.7km) of tunnel. In contrast, boring for the Channel tunnel started in June 1988, and the tunnels were opened to freight trains in June 1994 - 6 years for 50 km (31 miles) of much larger undersea tunnels, which allow transport up to 160km/h in real use (200 km/h being the highest designed speed). That's 5.2 miles per year, versus TBC's 1.1 miles per year, comparing like with like.

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#124

Post by trhway »

disambiguation wrote: post #113
qgin wrote: post #86

China: Builds 40,000 miles of high speed rail in 12 years https://twitter.com/xiaoyewen/status/1494588071483875333 United States: Thinks about vacuum tubes for awhile, gives up entirely.

Also somehow its easier to build self-driving cars than it is to invest in public transportation.

that is actually a competition between AI and collective public intelligence, where the first being a pure engineering problem with no limits for growth has been improving exponentially over mere decades while the second has been improving really slow over the observable millennia. So, i'd bet on AI :)

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#125

Post by tsimionescu »

panick21_ wrote: post #81
tsimionescu wrote: post #23

Earlier quoted context omitted.

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).

The 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/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 vacuu…

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.

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#126

Post by goldenkey »

hammock wrote: post #102
goldenkey wrote: post #57

Earlier quoted context omitted.

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.

And hyperloop has the potential to replace millions of gas-burning cars, buses, trains and planes...

It still has to be powered..so the gas-burning thing is a bit disingenuous.

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#127

Post by iab »

qgin wrote: post #86

China: Builds 40,000 miles of high speed rail in 12 years https://twitter.com/xiaoyewen/status/1494588071483875333 United States: Thinks about vacuum tubes for awhile, gives up entirely.

Look, we’ve tried nothing and we’re all out of ideas

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#128

Post by jmyeet »

parasense wrote: post #111
jmyeet wrote: post #36

Vacuum travel in a a tube does actually make sense. It may not be viable (yet?) but the idea is sound. A big problem is a breach in your vacuum. Keeping the atmosphere out is expensive. But what if where you’re building it has no atmosphere and is geologically stable or dead? Then a lot of problems go away. You don’t even need a tunnel necessarily. Yet another reason why colonizing the Moon makes 1000x more sense tha…

> Vacuum travel in a a tube does actually make sense. It may not be viable (yet?) but the idea is sound. I'm not sure the idea will be viable, ever. Too many problems, not enough rewards. For example, the problem of a vacuum tube developing a leak. The leak would start an implosion, which then propagates down both directions of the tube at mach-1 speed of sound. The implosion would resemble the continuous crushing of…

> The leak would start an implosion

This is a science fiction trope with no basis in reality. The pressure differential is one atmosphere to zero atmospheres which is functionally equivalent to one atmosphere to two atmospheres or what you get from diving 10 meters into the ocean.

The Apollo LEM had a shell that was pretty equivalent to aluminum foil in places. One atmosphere to zero atmospheres is the sort of thing you can plug up with duct tape.

Re: Hyperloop lays off half of its employees as it pivots away from passenger travel

#129

Post by panick21_ »

tsimionescu wrote: post #125
panick21_ wrote: post #81

Earlier quoted context omitted.

The 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/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 vacuu…

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 esse…

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.

Post reply on HN