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Comment Re:Emergencies? (Score 1) 223

I agree with you vacuum is not a particular big pressure differential to overcome.
But it would be a rather deep pool to get an similar differential, 1 atmosphere/bar (14.5 psi) is equivalent to 10 meters (30 ft) of water depth.
If this thing gets build in a place like The Netherlands it would no doubt be an underground tube and the forces of the overbearing soil and water are greater than the vacuum.
In such a construction most of the tube would be a regular concrete structure with something thin made of steel or plastic to make it air tight.
Yes there'll be a bow shock but easy to calculate and construct accordingly.

Comment Re:anyone know.. (Score 3, Informative) 160

A valid question.
But these days we do have metallurgical solutions.

During 1979-1980 I was involved in the testing of steam wells near the Vesuvius volcano in Italy.
The tapped reservoirs were between ~1200 and ~1800 meters deep and the bottom hole temperature was close to 350degC, on full flow around 250 degC at the wellhead..
Producing them caused a hellish noise and a lot of steam, we calculated the gross output of a single well was around 50MW.

After a while the measurements showed a rather serious problem, lot's of sulphur, heavy metals and other nasty minerals were included in the steam and eventually in the condensed water.
Cleaning this up would leave around 15MW of energy but it would be hugely expensive.
Although the wells still exist they have never again been produced.

Back to your question about the pipes used, in the day they were some Chrome alloy suitable for the expected temperatures and pressures but any serious corrosion would have a time factor.

I found it interesting that starting up the wells (very slowly and controlled) caused the wellhead to rise some 3 meters due to the heat driven expansion of the pipes. Shutting them down required the same kind of care.

Comment Re:Hey let's keep going... (Score 1) 83

An interesting look at the option re. language skills and I can see some truth in it.
At the same time I see the weakness of the British system, problems like lack of skills or pressure on the lower wages due to foreign cheap labour are not addressed by the national politicians but instead they blame others like Brussels, the Poles etc.

In other words, British press and politics jointly continue on the same path of deception they have been on since even before the days of Maggie Thatcher.

Comment Re: What would Trump do? (Score 1) 128

Our main manufacturing exports are jumbo jets and earth movers, and both do really well.

Uhhh:

Boeing had only netted three orders for the 747 this year. The sale almost doubles Boeing’s current backlog of 15 unfilled orders for the plane, according to the Chicago-based manufacturer’s website. The company said in July it was slowing 747 production output to six a year and would have to end the program if new orders didn’t materialize.

https://www.bloomberg.com/news...

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