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HS2 or gigabit internet?

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Should we fund HS2 or free gigabit internet connections to every household and business in the UK
HS2
14%
 14%  [ 1 ]
Free gigabit internet connections
57%
 57%  [ 4 ]
Something else
28%
 28%  [ 2 ]
Total Votes : 7

crissdee
1377081.  Thu Mar 18, 2021 12:28 pm Reply with quote

If I understand it correctly, which I think I do, Trident is a big f*ck-off rocket which can carry a number of things. This we buy from Uncle Sam. We then bolt on our home-made nuclear stuff.

 
Brock
1377083.  Thu Mar 18, 2021 12:37 pm Reply with quote

barbados wrote:
PDR wrote:
PDR wrote:
(no one sells nuclear weapons to anyone else anyway).

.........


The USA sells us Trident missiles.

PDR

I can't be the only one who doesn't understand this - and there has to be a logical explanation - but.
Is that not contradictory?


PDR has already explained it. The UK makes its own nuclear weapons, at the Atomic Weapons Establishment at Aldermaston. The USA sells us the delivery systems.

 
barbados
1377084.  Thu Mar 18, 2021 12:40 pm Reply with quote

crissdee wrote:
If I understand it correctly, which I think I do, Trident is a big f*ck-off rocket which can carry a number of things. This we buy from Uncle Sam. We then bolt on our home-made nuclear stuff.

That makes sense - it's just one of those "huh?" statements

 
PDR
1377085.  Thu Mar 18, 2021 12:51 pm Reply with quote

barbados wrote:
Not an expert, but don't we just launch them when required on behalf of the US?
i.e we don't "own" any missiles, but we do own the best equipment to launch them.


We "lease" the missiles (in the sense that the US contractor is responsible for depth maintenance on them), but we own the warheads and the submarines that carry them. We lease the missile control and targeting system (because we were too skinflint to buy the design rights)and when it first went into service the USA retained a "dual key" as part of the export license, but that was removed any years ago as being impractical.

PDR

 
suze
1385115.  Tue Jul 13, 2021 12:43 pm Reply with quote

This thread will do.

The good husband has been talking to a couple of professional contacts about HS2 today, and he has heard a part of the explanation for why it is quite so expensive which was new to him. We may need the physicists and/or the engineers among us.

The specification for HS2 requires the track to be engineered such that it can handle trains running at 400 km/h. The only trains in the world which reach 400 km/h are maglev setups in East Asia. No train powered by overhead electric cables - as HS2's trains will be - has ever reached that speed. But hey, there are European electric trains which reach 350 km/h so no harm in building a line which can handle the trains of the future, is there?

Well, yes, and this is where I need the physicists and/or engineers, because I don't completely understand what follows. Quite a lot of HS2 will be in tunnel to keep the NIMBYs happy, and according to Andy's professional contacts, this causes something called the Rayley Wave Speed to become relevant.

While the open air parts of HS2 will be built in the conventional way with the sleepers surrounded by gravel, the tunnel sections will have the rails set directly into concrete. The tunnels will also be concrete lined. This system is called "slab track", and is preferred inside new build tunnel.

Now, a train which travels faster than the Rayley Wave Speed will apparently sound like an earthquake, and will basically vibrate itself to bits. And the Rayley Wave Speed through concrete is thought to be in the region of 360 km/h. This was apparently not considered at the design stage, simply because railway engineers in Britain have no experience of trains which go fast enough for it to be relevant.

Does this mean that HS2 has been ludicrously over-specified, to handle trains faster than it will ever be able to accommodate?

 
Brock
1385116.  Tue Jul 13, 2021 12:55 pm Reply with quote

suze wrote:
...this causes something called the Rayley Wave Speed to become relevant.


I can't comment on the technical aspects but isn't it "Rayleigh"?

https://en.wikipedia.org/wiki/Rayleigh_wave

 
PDR
1385117.  Tue Jul 13, 2021 2:37 pm Reply with quote

It's the surface equivalent of the accumulation of shockwaves generated by a supersonic aeroplane that results in the "sonic boom" effect. The passing of the train generates a pressure wave in the rail which moves ahead of the train and dissipates. But if the train is moving faster than the wave propagates forwards then the wave falls back under the rest of the train which adds further energy to it, so it builds in magnitude to a single coincident pressure lump which can be very destructive. Where rails are carried on sleepers resting in ballast the natural movement and damping effect of the ballast does a lot to damp out the pressure wave, but this effect doesn't happen where the rails are mounted on a rigid surface (eg concrete). This is why trains are often observed to be noisier when crossing bridges, because the rails are carried rigidly and the rolling noise isn't damped out.

On a concrete surface hitting the Rayleigh Wave Speed can produce pressure waves that exceed the rupture strength of the concrete in the bed, causing cracking that rapidly accelerates to the point of complete failure.

I would be very surprised if it hadn't been considered, but would not be surprised if they had been told to ignore the requirement (on cost grounds) because a train would be unlikely to routinely use speeds in that range. This might be just a case of a new generation of design or project staff only just discovering the trade-offs that have been agreed by predecessors. That's something that occurs in my industry quite frequently.

PDR

 
Alexander Howard
1385118.  Tue Jul 13, 2021 2:42 pm Reply with quote

They have to put it in a tunnel through the Chilterns, because otherwise they will spoil all my favourite walks. They have wrecked one of my best already.

Could they (at yet greater expense) line the tunnel with baffles or something, and disrupt the concrete surface?

 
PDR
1385119.  Tue Jul 13, 2021 3:02 pm Reply with quote

Alexander Howard wrote:

Could they (at yet greater expense) line the tunnel with baffles or something, and disrupt the concrete surface?


Not really. The pressure wave is inside the concrete, not in the air above it. The surface of the concrete wants to be as flat as possible because any surface features would produce stress concentrations that would exacerbate the cracking.

PDR

 
suze
1385123.  Tue Jul 13, 2021 4:20 pm Reply with quote

Thanks PDR.

So the bottom line here seems to be that the line has indeed been over-specified. Electric trains capable of 400 km/h don't exist at the present time. Spain will be the first country to have them, or so the man reckons, but even if we do have them here in the future they won't be able to run on HS2 because Bad Things would happen if they did.

Now, it may be that building the line to accommodate 400 km/h isn't actually much more expensive than building it to accommodate 300 km/h and so they might as well. That goes well beyond Andy's knowledge let alone mine, but the guys he was speaking to didn't appear to think so.

This issue doesn't have to be considered for the ultra high speed maglev lines of East Asia since the trains float. It does have to be considered for the high speed electric railway lines of Europe, but they've gotten around it by using materials other than concrete to hold the rails. Technically feasible here, but too expensive for Boris's liking, is the suggestion.


Brock wrote:
I can't comment on the technical aspects but isn't it "Rayleigh"?


It certainly is! The Rayleigh in question was a peer, and his title was taken from the town near Southend.

Still, Rayley was better than my first thought on how to spell this word. Knowing that it was something to do with railways and not knowing that Rayleigh was someone's name, I originally perceived it as raily, a non-existent adjective meaning "like rail"!

The good husband put me right on that, but his excuse for Rayley is that he is a mathematician rather than a physicist and was thinking by analogy with Cayley. I am assured that the mathematicians among you will know who Cayley was!

 
PDR
1385131.  Tue Jul 13, 2021 5:35 pm Reply with quote

Someone whose hair was green and leaf-like?

Or are you referring to the grandfather or employer (accounts vary) of the world's first glider pilot?

PDR

 
suze
1385138.  Tue Jul 13, 2021 6:38 pm Reply with quote

Apparently not!

The world's first glider flight was made by either the grandson or servant (accounts vary) of Sir George Cayley Bt, who was for a time Whig MP for Scarborough.

The mathematician Andrew Cayley, who was a barrister until he was appointed Sadleirian Professor of Pure Mathematics at Cambridge, was apparently a distant cousin. I am reliably informed that he was an Important mathmo.

 
ali
1385139.  Tue Jul 13, 2021 9:10 pm Reply with quote

suze wrote:
The mathematician Andrew Cayley, who was a barrister until he was appointed Sadleirian Professor of Pure Mathematics at Cambridge, was apparently a distant cousin. I am reliably informed that he was an Important mathmo.


That's Arthur Cayley, and he is a grand fromage indeed in the world of mathematics - he has a set of numbers named after him (the 8-dimensional analogue of the quaternions, if you care about such things); and also Cayley tables, beloved of algebraists worldwide.

 
barbados
1385141.  Wed Jul 14, 2021 1:21 am Reply with quote

ali wrote:
beloved of algebraists worldwide.


There are people in the world that actually do algebra???
WOW!

 
ali
1385143.  Wed Jul 14, 2021 1:29 am Reply with quote

barbados wrote:
ali wrote:
beloved of algebraists worldwide.


There are people in the world that actually do algebra???
WOW!


There are three kinds of algebra:
Classical algebra - where letters stand for numbers
Modern algebra - where letters stand for mathematical objects other than numbers, and
Abstract algebra - where you don't know what the letters stand for, and you don't care.

Cayley is big medicine in the third kind.

Recently, to keep my brain working; I've been re-reading my abstract algebra books from my university days (it was always my favourite subject).

 

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