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The Hyperloop: BUSTED
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usagi:

--- Quote from: wraper on January 20, 2018, 01:12:59 pm ---
--- Quote from: amspire on January 20, 2018, 12:51:50 pm ---
--- Quote --- Another way is to have an object weighing tonnes travelling at 1000km/h come into destructive contact with a stationary tube.
--- End quote ---
It won't be head collision, and it will just bounce away from a wall.
--- End quote ---

--- End quote ---

objects travelling around 300m/s tend to behave quite differently than people are used to in normal everyday life, maximum of 26.8m/s.

one of my hobbies deals with objects normally travelling at 300m/s or more. objects don't bounce like you think they do. any contact at those velocities will be catastrophic.

regardless, hyperloop is a silly impractical pipe dream.
HalFET:

--- Quote from: amspire on January 20, 2018, 12:39:17 pm ---
--- Quote from: wraper on January 20, 2018, 12:35:49 pm ---
--- Quote from: amspire on January 20, 2018, 12:21:02 pm ---Let's say they can travel at 1000km/h. The tubes have to be safe. There has to be a safe distance between tubes so a crash in the Up tube can't take out the Down tube. A safe separation may be 100 meters. That is not the worst part. It has to be safe for people in the proximity of the tunnels. A safe distance exclusion zone could be 400 meters? I do not know but we are talking  a possibility of a big high energy collision with shrapnel - it could be 1 km or more. So when they build the London to Edinburgh hyperloop that they talk about, are they going to build a corridor 2 km wide all the way through the heart of England? Even putting the tubes in trenches will not stop shrapnel flying for massive distances.

Talking about putting solar cells on top of the tunnels is a total joke if you are going to have 1km each side unoccupied.

--- End quote ---
Safe distance, LOL? By same merits, you would need to keep people away from usual high speed train at least a few km away as well  :palm:

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No. A high speed train derailment is not an explosion. A Hyperloop crash can easily be an explosion. Totally different.

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amspire, please do the math before you dream up explosion horror scenarios, lets go over the numbers:
A filled shipping container would weigh in at around 30 000 kg (more typical would be around 24 000 kg I'd expect), lets say it travels at the 1000 km/h as you seem to indicate. For a train travelling at 400 km/h to have the same kinetic energy it'd only need to weigh in at 187.5 ton. In comparison a TGV passenger train weighs in at about 380 ton, so it'd have even more kinetic energy than your hyper explosive container while travelling at 300 km/h. This still pales in comparison to the kinetic energy of an passenger or cargo jet at cruise speed, which is easily 10 times more still!

And the aluminium on fire one is a classic argument, honestly you'd have to do some pretty impressive stuff to set it off, not even incendiary weapons manage, nor does a pure oxygen atmosphere do the job easily, unless we're talking powdered aluminium. And believe me, given how many vehicles are built out of aluminium, the military has probably tried thousands of times to figure out ways to do it...
nctnico:

--- Quote from: amspire on January 20, 2018, 12:21:02 pm ---
--- Quote from: EEVblog on January 20, 2018, 11:15:06 am ---
--- Quote from: wraper on January 20, 2018, 10:52:13 am ---
--- Quote from: EEVblog on January 20, 2018, 03:28:37 am ---Rubbish. uBeam and Solar roadways can both work in theory and also in practice, demonstrably so, that's a fact. They are just impractical.

--- End quote ---
In theory they are very inefficient way of using already existing technologies. Therefore I say they don't work in theory.

--- End quote ---

Nope, they can both be reasonably efficient enough in theory and kinda in practice even, just not under practical usage circumstances.
But it's semantics of course.
The idea of keeping a 1000km long several meter wide vacuum system working with a 1000km/h projectile in it is just madness.

--- End quote ---
The 1000km/h is a number not based on any safety testing. You can buy a car that can go at 440 km/h but that does not mean that it is safe to regularly travel anywhere at 440 km/h. The safe speed tends to come from experience, but in Australia, for example, they have settled for speeds varying between 70 and 110 km/h outside urban areas.

Let's say they can travel at 1000km/h. The tubes have to be safe. There has to be a safe distance between tubes so a crash in the Up tube can't take out the Down tube. A safe separation may be 100 meters. That is not the worst part. It has to be safe for people in the proximity of the tunnels. A safe distance exclusion zone could be 400 meters? I do not know but we are talking  a possibility of a big high energy collision with shrapnel - it could be 1 km or more. So when they build the London to Edinburgh hyperloop that they talk about, are they going to build a corridor 2 km wide all the way through the heart of England? Even putting the tubes in trenches will not stop shrapnel flying for massive distances.

--- End quote ---
Your reasoning sounds much like the scaremongering when steam trains, automobiles and airplanes where introduced.  :palm:
If you'd reason like that then every airport in the world should have a clearance of a 50km radius and the terminal buildings should be bunkers made from reinforced concrete!
amspire:
None of the examples you are quoting are travelling very close to a thin stationary tube. In a high speed train was stopped dead in a few seconds, you would have a major explosion.

A fully loaded shipping container that was out of control could easily rip apart any sort of tube they are contemplating. I think you are kidding yourself if you are imagining that every possible accident will result in a nice controlled sliding along this fragile tube for a minute or more at this speed.

You want some numbers?

1000km/h is a bit under 300m/s. Lets call it 300 m/s. A shipping container can be 36 tonnes and a carriage capable of carrying it, propelling it and doing emergency stops would probably weigh something similar. So lets say a total of 50 tonnes.

The energy of the moving carriage is 1/2 x 50000 x 300 x 300 = 2GJ. If something broke causing a violent rotation of the load so that it ripped trough the tube, the motion would mostly stop fairly quickly. It would only take a second or so to reach the next support. If most of that 2GJ is dissipated in 10 seconds, that is 200MW of power released over that 10 seconds. That is enough to make things incredibly hot. How is that 2GJ/200MW disippated?

According to my rough calculations that might be wrong, this is enough energy to melt 3 tonnes of steel.

If a carriage hit another stationary carriage in front at 1000km/h, it would be the same explosive energy as half a tonne of TNT. How close is it safe to be next to a half tonne TNT explosion in a steel tube? It would be a pretty spectacular pipe bomb.

This is nothing like your experience of seeing a car crash.
nctnico:
A Boeing 747 at 800km/h weighing 350 metric tonnes has a kinetic energy of over 17GJ.
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