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Old 2020-12-02, 03:19   #45
Dr Sardonicus
 
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This article has a lot of pictures, both before and after collapse. The last picture in the article, an AP photo, shows the underside of the reflector after it was damaged in August.

A number of reports say, and pictures in the above-linked article confirm, that the tops broke off all three support towers.
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Old 2020-12-02, 04:37   #46
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Scott Manley's video explains what happened.
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Old 2020-12-03, 20:49   #47
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US National Science Foundation has released video of the collapse happening.
https://www.nsf.gov/news/special_reports/arecibo/
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Old 2020-12-03, 21:04   #48
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So how long would it take to rebuild it? They could clean up the mess, and use whatever salvagable parts are left to build a new one, as well as making it more sturdy. Shouldn't be as hard as it was when they first built it (technology has improved).

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Old 2020-12-03, 21:31   #49
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Oh well. It was too small and old anyway. Next task is to convince the powers that be that a replacement is vital to defending the US from China / Covid19 / terrorism / space rocks.
As an engineer, I would advise against reusing parts of a failed instrument that are approximately as old as me.

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Old 2020-12-03, 21:44   #50
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Quote:
Originally Posted by kriesel View Post
Oh well. It was too small and old anyway. Next task is to convince the powers that be that a replacement is vital to defending the US from China / Covid19 / terrorism / space rocks.
As an engineer, I would advise against reusing parts of a failed instrument that are approximately as old as me.
There are no parts left in a reusable state beyond melting down as scrap. Even the towers snapped off at the top.

It fell from a height of 137m and hit the ground at very high speed.
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Old 2020-12-04, 00:18   #51
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Quote:
Originally Posted by kriesel View Post
Oh well. It was too small and old anyway. Next task is to convince the powers that be that a replacement is vital to defending the US from China / Covid19 / terrorism / space rocks.
Careful. In today's politically-charged, scientifically-challenged world, such an instrument could just as likely be construed as *causing* Covid19. Just like 5G.

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Old 2020-12-04, 02:22   #52
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Quote:
Originally Posted by kriesel View Post
Oh well. It was too small and old anyway. Next task is to convince the powers that be that a replacement is vital to defending the US from China / Covid19 / terrorism / space rocks.
As an engineer, I would advise against reusing parts of a failed instrument that are approximately as old as me.
"Defending the US" is absolutely on point.

The original construction of the Arecibo Telescope was done as part of the DEFENDER missile defense program, so had military funding, as well as engineering assistance from the US Army Corps of Engineers.

Defending against space rocks is a real present and future concern which has already been mentioned twice in this thread (first by Uncwilly, who pointed out the telescope's unique capabilities and favorable geographical location for the purpose).

Though not an engineer, I agree the only option for rebuilding is starting over from scratch.

I saw a 350-million dollar estimate for replacement. My instincts say it would be much more.

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Old 2020-12-04, 03:59   #53
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Quote:
Originally Posted by Stargate38 View Post
So how long would it take to rebuild it? They could clean up the mess, and use whatever salvagable parts are left to build a new one, as well as making it more sturdy. Shouldn't be as hard as it was when they first built it (technology has improved).
It certainly has but there is usually some lost as well. Roman concrete was formulated to harden in water. As a result their bridges still stand after couple of millennia as opposed to today's recipes which do not set in water and generally have much shorter expiry dates.
In olden times telescope crosshair were made of spider web, the knowhow of which is lost to time:

https://en.m.wikipedia.org/wiki/Reticle
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Old 2020-12-04, 04:21   #54
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Quote:
Originally Posted by a1call View Post
It certainly has but there is usually some lost as well. Roman concrete was formulated to harden in water
My understanding is Roman concrete is a known thing and able to be reproduced, But it is not used, because there is not a desire to go through with the expense and effort to make it. Controlling the heat of the reaction of concrete curing is a known thing. Hoover Dam had cooling tubes built in. The interior of the mass of the dam has yet to reach its final strength. It is estimated that it will finish curing in 500 years and will have a lifespan of 1500 years after that.

https://www.sciencemag.org/news/2017...asts-millennia
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Old 2020-12-04, 08:57   #55
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Quote:
Originally Posted by Dr Sardonicus View Post
I saw a 350-million dollar estimate for replacement. My instincts say it would be much more.
Probably pretty good instincts.

During WWII there was a debate over the cost and effectiveness of British bombing of Germany. Precision was notably lacking, so it was done fairly indiscriminately. The pessimists said it would cost more in lives and treasure than it was worth, while the optimists said it was worthwhile and would shorten the war. Crew and craft mortality was high, as was German civilian death rate. After the war its effectiveness was evaluated using captured German documents, and determined the optimists were too optimistic in their estimates by a factor of 11, while the "pessimists" were too optimistic by a factor of "only" 6.

During the early days of planning the US superconducting supercollider, initial estimates were ~200 million dollars. One of the physicists said nonsense, it will be at least 600 million. No one believed him. The project was canceled after the estimates for total cost to completion had risen to 12,000 million and over 2,000 million had already been spent.

Space shuttle payload to orbit cost was initially estimated as $1109/pound, but actual was over $37,000/pound. Estimated cost/flight was $260 million; actual was $1642 million.

Last fiddled with by kriesel on 2020-12-04 at 09:03
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