General > General Technical Chat

The end of the line for the Arecibo radio telescope

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LaserSteve:
If you love RF, this may make you cry.. Tech details toward the end.

https://youtu.be/IqGnnpwEwug

Steve

Bud:
The aliens must be scratching their heads (or whatever ) why that transmission was suddenly lost.

Ian.M:
Its deeply suspicious that the main suspension cables were painted white near their anchors to the platform.   Some dumb administrator must have decided to paint the ugly cables which would have been showing signs of surface rust, and once the paint was on them failure was inevitable.

Back when Arecibo was built, there were still plenty of 'greybeards' in the rigging industry who'd served their apprenticeship working on the rigging of large square rig sailing ships, and the maintenance requirements for 'plough steel' static rigging in hostile environments were well known.  However as stainless steel ropes and cables have displaced plough steel ones for most static rigging, this common knowledge has largely been lost.

Its well known that wire rope in dynamic applications requires lubrication.  Its far less well known that contrary to the best practices for stainless wire rigging, its *ESSENTIAL* to lubricate 'plough steel' wire static ropes and cables, preferably with a penetrating lubricant with anti-corrosion properties, to reduce corrosion and prevent the strands fretting against each other as the load varies and the cable stretches.  The paint coating will have trapped water in the core of the cable, and prevented any applied lubricant from penetrating, resulting in rapidly accelerating corrosion of the strands.

tom66:
Wasn't this a similar issue with the Ponte Morandi collapse?  The cables were encased in concrete because they were 'ugly' which precluded any inspection of them.  The concrete traps moisture and has a corrosive effect itself.

Ian.M:
Each cable  should have been replaced as soon as there was significant distortion or more than three broken strands in a short length or two at the terminals.
https://www.unionrope.com/Portals/0/Documents/Technical/Crane/when-to-replace.pdf

Its obviously been running with little safety margin for many years and in recent years, allowing personnel access to the platform or under the dish, other than for essential structural maintenance, was criminally negligent.

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