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In the article Hyperloop: the doubts persist, it is claimed that the hyperloop could implode due to a crack in the tunnel wall. The argument is supported by the claim that air would rush in at the speed of sound.

The atmospheric pressure on the tubes under vacuum would be 10 tonnes per square metre, basically the weight of a lorry. With just the slightest crack, outside air would enter the tubes at the speed of sound, and the infrastructure would implode.

I fail to understand how an increase in internal pressure, (1.)assuming it's still below the external pressure) would cause a tubular structure to implode, since (2.)generally at an implosion, the external pressure generates a failure mode of the structure.

What I can imagine is that the relatively (w.r.t. the structural design) large forces and intense aerodynamics create resonance which could trigger a failure mode, which in its turn could lead to failure of different sections in the form of an implosion, but it seems to me that such a conclusion would require very detailed (computational) analysis, something that is not referenced. On top of that it would (3.)likely also depend on design details/iterations which appear to not yet be available.

Discussion of assumptions:

  1. Due to the large velocity of the incoming airflow, it could be possible that locally the internal pressure could temporarily exceed the external pressure, but I do not have any reasons to assume that would be the case.
  2. Theoretically a design which experiences buckling under external pressure and a different failure mode such as "tension failure"/yielding under internal pressure and a material could perhaps be selected to fail in failure mode 2 with very low stresses compared to the stresses required for failure mode 1. Though this seems irrelevant in this discussion.
  3. If it is a known phenomena for just 3 single plain cylinders in series to all implode if 1 suffers a leak/crack under a vacuum, then it might not be necessary to have a complete analysis of the tubing system.

So in order to verify this claim based on empirical evidence, my question is: is it a normal/known phenomenon for vacuum tubes/spaces to implode when they get a single crack?

Up till now I have not found documentation of such events, when searching on tags: implosion, leaks, cracks.

closed as off-topic by Jan Doggen, Oddthinking Aug 26 '18 at 20:24

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    I'm not sure this is the right site for this question - this site is about fact-checking claims using empirical evidence, and it's not possible to empirically fact check a speculative argument about a class of theoretical designs that haven't actually been built. It might be on-topic at engineering.stackexchange.com but check their policy on questions about theoretical designs first – user568458 Aug 26 '18 at 14:19
  • Thank you for your response, even though it might be very hard to prove that it cannot implode, it would be quite easy verify the claim if the phenomena in assumption 3 is found. That would be a fact check of a claim, using empirical evidence with a positive outcome. However, in case that phenomena is not found, I agree with your point, and then it would perhaps be more suitable on for example Engineering. Currently I do not exactly know how to deal with the relation between that uncertainty in relation to the "on-topic-ness". I am looking into that. Thank you for the critical feedback! – a.t. Aug 26 '18 at 14:26
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    It's the shock wave: washingtonpost.com/news/morning-mix/wp/2018/08/16/… – Daniel R Hicks Aug 26 '18 at 14:38
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    It's not really about the internal pressure changing - it's just the generic fact that any object under load may fail catastrophically if the structure breaks down at a single point. Try breaking a stick sometime, or popping a balloon. For the specific case where the load is caused by vacuum, you can find any number of videos on YouTube of glass vacuum bottles and CRTs imploding when cracked. Whether that would happen with a hyperloop tube depends on how it would be constructed - certainly there are design techniques that would help avoid that phenomenon. – Nate Eldredge Aug 26 '18 at 14:49
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    I'm voting to close this question as off-topic because it is asking for an engineering analysis of a structure that hasn't been designed yet. – Oddthinking Aug 26 '18 at 20:24

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