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The Hyperloop: BUSTED
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FreddyVictor:

--- Quote from: TerraHertz on July 25, 2016, 04:15:35 am ---Added:

--- Quote from: blueskull on July 25, 2016, 04:00:30 am ---The fallen one, if my memory serves me correctly, is an AirFrance one. The poor thing was hit by a debris coming from a poorly maintained PanAm.
The ultimate reason of Concorde being phased out, IMHO, is solely for cost reasons. By that time, new generation B767 and B777 have astonishing fuel efficiency and can also offer smooth traveling experience.

--- End quote ---

It was a bit of metal debris lying on the runway from a previous plane. Sucked into an engine of the Concorde on takeoff, turbine disintegration ruptured a wing fuel tank. Fire caused structural failure before it could make it to any landing site.
But yes, the accident was an excuse to quit Concorde flights, that were actually no longer profitable.

--- End quote ---
<edit>LazyJack has it already

I did read that 9/11 resulted in a drop off of business travellers which made the service un-economic  :(

on-topic, the only MAGLEV I've been on was the one at Birmingham International (gone now I think) and it left alot to be desired !
HP-ILnerd:

--- Quote ---To a limited extent, you could. The issue comes down to the practicality of such a safety mechanism. It would require a complex array of sensors and mechanisms in order to adequately seal and safely repressurise the system. The issue is there are too many single-points-of-failure.

--- End quote ---

Why would it have to be complex?   A leak sensor system (required one way or another) wouldn't have to measure pressure, just that there is pressure.  Not off-scale low, just anywhere on-scale means a leak.  You could even make it triply redundant if you like.  I just priced some pressure transducers at DigiKey, and even 10's of thousands of them wouldn't register as budget noise in a multi-billion dollar civil works project.


--- Quote ---The key here is 'controlled fashion'. It requires many complex systems all working correctly to acheive this. It's not impossible, but grossly impractical. Remember: these safety mechanisms would need to be replicated the entire length of the hyperloop.

--- End quote ---

Again not seeing the complicated?  They don't even have to talk to each other, but you'd want them too because they could react faster if they did.  A backup "we can't communicate" mode where they all reacted passively should be possible.  Any one segment letting air in because it smelled a leak would trigger adjacent ones in a cascade fashion whether they could talk or not.  Again, the expansion sections seem ideal locations to put them.  You need to have pumps at each one to evacuate it in the first place, right?  Nobody would design it with one pump for the whole system at each end, right?  It'd take eons to pump down.  So you already have valves at each pump.  If they failed, you could simply have an explosive bolt fire (purportedly one of the most reliable gadgets in the world) and leave a hole of prescribed size through which air could flow.  There's your precisely controlled repressurization.  The new air in the tube would act as a buffer against the uncontrolled air from the catastrophic breach.  Considering the wiring/plumbing/HVAC,etc. in the average American Skyscraper, I don't see this as being orders more complex.


--- Quote ---Again, such safety mechanisms are possible, but impractical, and would be expensive. They would add to the cost of maintenance and upkeep of the system and should any part of the system be offline for maintenance or malfunctioning, the entire system would be potentially unsafe to a catastrophic failure. From what I've seen of the projected construction costs, it seems unlikely these sort of safety mechanisms have been taken into consideration.

--- End quote ---

Every building of any size in the US is required to have a fire suppression system and automatic fire-doors that trigger automatically if one of the sensors pops (usually from measuring a pressure drop) or the alarms go off.  This seems virtually identical, and differs only in being spread out.  The system would require maintenance under normal circumstances, so it would need to be able to re pressurize in a controlled fashion anyway, right?

Thunderf00t is a pretty smart guy, and he may have had lots of experience working with vacuum, but (and I don't know the answer to this) has he ever worked on a large device that had to defend itself in the event of failure?  He seemed to be implying his apparatus was an actual fair representation of a working system.
optoisolated:

--- Quote from: Brutte on July 25, 2016, 08:03:12 am ---The idea that if the tube gets ruptured at any place and people inside die instantly because of the vacuum is also flawed. The capsules are pressurized and if the tube is punctured and filled with atmospheric air (gradually, via size-limited hole) then the drag would increase gradually and the capsule would eventually slow down. For God's sake that is not 600km of single piece of pipe and some locks are needed  |O
--- End quote ---
This would be dependent on the location of the rupture, and where the carriage was in relation to that rupture. While a small rupture, as long as it didn't lead to some form of cascading failure of tube, could be handled, where I see concern is the rotational energy of the turbine being designed for the extreme low pressure of the tube suddenly (within a few seconds) of denser air. That would result in not insignificant anti-torque on the engine. That rotational energy would be transferred to the structure of the carriage, potentially deforming it. This could be tolerated within limits, but any significant sudden re-pressurisation would potentially be catastrophic for a turbine.


--- Quote from: Brutte on July 25, 2016, 08:03:12 am ---As of the emergency exiting, I think it should be presented in relation to emergency exiting when KLM + Pan AM meet on one runway. How about then?
--- End quote ---
No-one is saying airline travel is completely devoid of risk. Incidentally that article also references all of the safety improvements that have been implemented as a result of that accident.The airline industry has a proven track record of improving its safety over time. Perhaps after 100 years of development, we may be technologically in a position where the hyperloop could be feasible. None of this rules out the concept, but does illustrate how impractical it is.
LazyJack:
Before we all go ahead and solve all possible engineering challenges of Hyperloop in this topic. Do not forget, that the set of engineering problems that may be solved is much much larger that the set of problems financially feasible to solve. Since eventually someone has to pay the bill, that is a very big limiting factor. Would a government (or crowd funding, or investors somehow convinced) commit unlimited money, I bet Hyperloop would come very quickly into existence, just as the Moon landing happened.
Look at for example microelectronics. The astronomical cost of a new generation fab is now much more limiting in getting more transistors squeezed on a chip than physics itself.

Of course, there is an other aspect of getting investors with false claims, then grab the money and run. But that is not engineering, but simple fraud, dressed into a nice engineering dress. I'm not saying that Hyperloop is this, but this is definitely a high profile case of creating the "we can solve anything, just give me money" type image.
EEVblog:
Can someone please explain to me the requirement for the Hyperloop (apart from being cool), with all it's inherent engineering problems, over a MegLev train?
Sure it's potentially twice the speed (so they claim), but what else? Nothing, just downsides. MagLev exists, works, is fairly robust, and has only had one(?) fatal accident, and that was a collision cause by human error.
Heck, what's that passenger capacity vs the two? MagLev might actually have greater throughput. The Shanghai one is 574 passenger capacity.

With all the ridiculous engineering requirements and potential failure points worth twice the speed? (even if it was possible)
Again, it's like Solar Roadways, solar panels aren't nearly as sexy an idea, but infinitely more practical.
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