General > General Technical Chat
The Hyperloop: BUSTED
HalFET:
--- Quote from: hayatepilot on January 16, 2018, 01:53:15 pm ---
--- Quote from: nctnico on January 16, 2018, 11:16:48 am ---
--- Quote from: EEVblog on January 16, 2018, 10:36:55 am ---
--- Quote from: nctnico on January 16, 2018, 10:10:13 am ---Since some revived this old thread I watched the video in the first post. I find it cringeworthy. Commercial airliners are made of aluminium composite material and they deal with similar pressures safely so why is that suddenly a problem for the hyperloop?
--- End quote ---
I'm not a mechanical engineer, yet I can think of many show-stopper problems and why this comparison with planes is not meaningful.
--- End quote ---
The airplane is just an example of a pressure vessel made as light as possible and yet it withstands similar pressure differences like the hyperloop is supposed to do. Actually an oil or gas pipeline is pretty much comparable to the build scale of a hyperloop tube (and oil and gas pipeline use much higher pressures). It is not like they are building something completely new. For once don't ignore the fact a lot of very smart people are working on building hyperloops allover the world and have working prototypes. Now it all comes down to whether it makes sense economically or not (which intrinsically means getting it safe to operate).
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The problem with the pressure difference is not with the pod but with the tube!
It is very important whether the pressure differential is positive or negative. If you have a vacuum inside a tube the walls must be very thick to prevent buckling. And if the tube gets kinked enough then the whole tube collapses in on itself.
If the pressure is on the inside then the tube can withstand much higher pressure differentials.
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Heh, these assumptions are a bit of a fallacy in some ways. You could design around this to prevent catastrophic failure by taking for example a double walled tube with sections which fail in a controlled manner. (e.g. perforated inner tube with foam and reinforcement rings around it inside the tube that acts as the "pressure vessel") That way the failure would be a lot more gradual and a lot safer. Keep in mind folks, we're engineers and not nay-sayers, which isn't to say this is very ambitious, but to outright shoot it down based on simplistic assumptions seems a bit low. The math on this points at it being a lot more feasible than solar roadways for example... I've seen more questionable things than this succeed before.
wraper:
--- Quote from: hayatepilot on January 16, 2018, 01:53:15 pm ---The problem with the pressure difference is not with the pod but with the tube!
It is very important whether the pressure differential is positive or negative. If you have a vacuum inside a tube the walls must be very thick to prevent buckling. And if the tube gets kinked enough then the whole tube collapses in on itself.
If the pressure is on the inside then the tube can withstand much higher pressure differentials.
--- End quote ---
FWIW, usual tunnel tubes must withstand much higher outside pressure than miserable 1 bar in case of hyperloop.
http://www.cowi.com/menu/service/bridgetunnelandmarinestructures/tunnels/documents/021-1700-020e-10b_tunnelengineering.pdf
--- Quote ---Great Belt
The Great Belt tunnel is to date the world’s
deepest tunnel in soft soil conditions and under
the sea.
The challenge was to design the tunnel lining
for extraordinary conditions with regard to
outside pressure and chemical aggressivity and
also to design joints to be resistant to the ambient
water pressure (8 bar).
--- End quote ---
--- Quote ---The TBM is required to operate in open or
closed mode in extremely variable geological
and hydrogeological conditions with water
pressures corresponding to 130 metres head of
water. As such, the TBM was designed to be
able to excavate short distances at up to 13 bar
pressure.
--- End quote ---
wraper:
--- Quote from: jonovid on January 16, 2018, 04:11:40 pm ---this 285 mph - 500km/h japanese maglev train looks like a lot safer way to travel.\
--- End quote ---
Expensive as hell, and not nearly as fast.
technix:
--- Quote from: EEVblog on July 25, 2016, 12:36:18 am ---I've been on a MagLev train at 430kmh.
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There is a single city with a 430km/h maglev... when did you visit Shanghai?
orion242:
--- Quote from: wraper on January 16, 2018, 06:06:04 pm ---FWIW, usual tunnel tubes must withstand much higher outside pressure than miserable 1 bar in case of hyperloop.
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All underground where expansion is less of an issue since temps remain constant and they are not steel. Nothing stopping them from taking the hyperpoop underground. Might take a few generations before we see a cross country underground tube network.
I also don't think TBMs can work in all soil types either.
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