Author Topic: The end of the line for the Arecibo radio telescope  (Read 18382 times)

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Online Ian.M

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Re: The end of the line for the Arecibo radio telescope
« Reply #25 on: November 27, 2020, 05:54:13 pm »
Its also a matter of access.   You'd need to get heavy lifting equipment in place to relieve the load on the cables.  I suspect the nearest >1000 tonne mobile cranes are in the USA or Mexico and even assuming you could get three big enough cranes on the quay in San Juan with enough time to do the work (there's only seven months till the next hurricane season), getting them up the road to the observatory (Highway 625) and emplaced just outside the rim of the dish between the towers, avoiding the danger zone would be a challenge in itself.

You'd also need to design a method of grappling or getting slings on the antennae platform that doesn't put the workers at unacceptable risk.
 

Offline Nauris

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Re: The end of the line for the Arecibo radio telescope
« Reply #26 on: November 27, 2020, 07:29:46 pm »
Photographs show that the remaining cables have already had strands break due to excessive strain.
That must be from corrosion/fatigue or past overload. If there were strands breaking from static load it would already be on the ground
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The structure could collapse at any time.
But why would it collapse at any time? I think it most probably comes down when there is some small extra stress acting on it like a gust of wind. So if it survived a windy day it is unlikely to come down following calm day and that is exactly the moment repair crew should be working on it.

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It would take too much time, and cost too much considering available funds.
I don't think it takes more than a week or two. Few kilometers of steel rope and a group of brave spanish men in Puerto Rico getting things done cost way less than those worry worry engineers and managers currently overanalyzing it and making straightforward things sound impossible. After all it is still up just needs some cables reinforced.
« Last Edit: November 27, 2020, 07:35:13 pm by Nauris »
 

Offline Gyro

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Re: The end of the line for the Arecibo radio telescope
« Reply #27 on: November 27, 2020, 08:11:31 pm »
But why would it collapse at any time? I think it most probably comes down when there is some small extra stress acting on it like a gust of wind. So if it survived a windy day it is unlikely to come down following calm day and that is exactly the moment repair crew should be working on it.

It does seem pretty unlikely that, with a static load of 900 tonnes, stretched out at an angle too, the additional weight of a couple of people going out to attach the end of an emergency support cable would trigger a sudden collapse.

The crew could maybe be on safety lines from a helicopter too.


P.S. Mind you, I'm sitting in an armchair!
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Online Ian.M

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Re: The end of the line for the Arecibo radio telescope
« Reply #28 on: November 27, 2020, 08:29:44 pm »
Due to the geometry, there's far more than 900 short tons (approx 820 metric tonnes) load on the cables.   You can find some details of the geometry here: https://www.naic.edu/~astro/aotms/performance/StructureDynamics.pdf


One of the problems is a cable under tension will whip violently if it breaks, and anyone in the way of a steel one as large as the Arecibo platform uses when it lets go would most likely end up as a chunky bloody splatter, and any helicopter could be swatted out of the sky.   

Also, if the cables have been weakened enough that there is insufficient remaining redundancy, its no longer possible to slack off one cable at a time and replace it to the same anchor points, so cable replacement becomes vastly more complex, putting more people in the high danger zone for longer.
« Last Edit: November 27, 2020, 09:50:29 pm by Ian.M »
 
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Offline David Hess

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Re: The end of the line for the Arecibo radio telescope
« Reply #29 on: November 27, 2020, 09:43:20 pm »
Photographs show that the remaining cables have already had strands break due to excessive strain.

That must be from corrosion/fatigue or past overload. If there were strands breaking from static load it would already be on the ground.

The strands were broken from the two recent overload events.

Quote
Quote
The structure could collapse at any time.

But why would it collapse at any time? I think it most probably comes down when there is some small extra stress acting on it like a gust of wind. So if it survived a windy day it is unlikely to come down following calm day and that is exactly the moment repair crew should be working on it.

It could collapse because the remaining cables are damaged and in an uncertain condition.

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[A] Few kilometers of steel rope and a group of brave spanish men in Puerto Rico getting things done cost way less than those worry worry engineers and managers currently overanalyzing it and making straightforward things sound impossible.

The physics and engineering are straightforward.  The weights are known and the geometry can be measured from a distance to calculate the strains involved.  Photographs show that the remaining cables have been stressed beyond their safe limit.

"Management" is who allowed deterioration of the structure to proceed over the past 13 years of no maintenance.
 

Offline james_s

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Re: The end of the line for the Arecibo radio telescope
« Reply #30 on: November 27, 2020, 09:50:20 pm »
People crazier than I have certainly attempted more dangerous stunts than that, even for no more gain than having accomplished the stunt. I would be more willing to climb up onto that platform to attach some cables than to attempt to climb up Mt Everest for example. Personally I would not want to do either one, but replacing the cables to save this thing from collapse seems far more useful.

How much does the suspended structure weigh? Is it within the realm of what could be lifted straight up by a large heavy lifting helicopter? If so either lift the thing up, cut the cables and then set it aside on the ground, or lift it to take the load off the cables just long enough for a crew to rush out and attach already prepared replacement cables.
 

Online Ian.M

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Re: The end of the line for the Arecibo radio telescope
« Reply #31 on: November 27, 2020, 10:11:33 pm »
Its two orders of magnitude heavier than any helicopter can handle.  I suspect the next thing that will happen is that a demolition plan will be put forward, probably by dynamiting the ground anchors of the tower restraining cables, and the tower bases to trigger an inwards collapse.
 

Online coppercone2

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Re: The end of the line for the Arecibo radio telescope
« Reply #32 on: November 27, 2020, 10:11:58 pm »
900 tons, you would need like 60 hinds lol

you would probobly need to build a temporary structure under it, I have my doubts even about cranes. thats why i suggested the 3d printed concrete tower
 

Offline rdl

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Re: The end of the line for the Arecibo radio telescope
« Reply #33 on: November 27, 2020, 10:30:57 pm »
There's still a lot of infrastructure there and the site is obviously ideal for a telescope of that type, why not just rebuild? Maybe the towers can be reused.
 

Offline TerraHertz

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Re: The end of the line for the Arecibo radio telescope
« Reply #34 on: November 27, 2020, 11:50:02 pm »
The strands were broken from the two recent overload events.

Sorry for lack of a link, but somewhere in the various videos I've watched about this recently there was a short sequence of pictures of the cables, taken by drones.

They are a mess. Steel multi-stranded cables, several inches thick, in which there is a lot of internal rusting causing random bulges. The spreading of the strands causes uneven stress on the strands, and together with the corrosion, results in LOTS of broken strands. Many, many places where there are broken strands sticking out like hairs.

So when they say the entire structure could collapse at any time and it's too unsafe to work on, they don't mean the extra weight of workers could make it fall. They really mean it could go at any moment. It has no remaining redundancy, and strengths of the remaining cables are continually reducing due to corrosion and ongoing strand breaks.

The final failure mode would be completely unpredictable, but will likely involve huge cable whipping around, the antenna falling in some random arc, and the support towers falling over dragged by unbalanced cables. No one is going to go anywhere near it. No helicopters, no building an emergency support tower under the antenna, and even walking around under the dish meshwork is a death sport at the moment.

I'd think even controlled demolition by placing cutting charges on all the cables so they can be dropped in one go, would be an extremely dangerous job.
Collecting old scopes, logic analyzers, and unfinished projects. http://everist.org
 
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Online coppercone2

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Re: The end of the line for the Arecibo radio telescope
« Reply #35 on: November 28, 2020, 02:01:10 am »
drones can put radio charges on the wires, or haul control wires out there, so it falls right in the middle, then you can put a new transmitter on it. you could use the control system of a TOW missile connected to a drone (it is long and safe and light with a cable length of 4km). you can make them like horse shoes that are placed over the wires, and you can put two of them on each end and sequence it so the wire falls down strait rather then being cut and then dragging through the reflectors on the bottom, to minimize damage. or use helicopters to hold the wires after they are cut to bring them off to the side without damaging the reflectors on the bottom. attaching the wire to a helicopter might be dangerous because you don't know how much strain it will get rid of and how it will shake when its cut, it would need alot of slack and a protection to release itself if it tried to yank on the helicopter. the less you screw up the bottom the more economical it would be to rebuild the top part. 
« Last Edit: November 28, 2020, 02:08:27 am by coppercone2 »
 

Offline james_s

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Re: The end of the line for the Arecibo radio telescope
« Reply #36 on: November 28, 2020, 02:28:49 am »
I don't understand how it got THAT bad without anyone noticing that failure was imminent. Rust of cables like that doesn't happen overnight. At least it isn't just in my country that so many people defer maintenance until it becomes a huge expensive problem. I know multiple people who kept putting off having the timing belt on their car engine changed until it snapped and destroyed the engine. People do the same thing with oil changes.
 

Online Ian.M

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Re: The end of the line for the Arecibo radio telescope
« Reply #37 on: November 28, 2020, 03:45:30 am »
The dish reflector would be totally FUBARed if you dropped the platform onto its center.   Its held up by radial suspension cables under it from the rim, and they'd all whiplash.  Even if the individual panels remained attached, didn't buckle and you could splice the dish suspension cables, after nearly 60 years most of the panel adjustments would be seized, so you'd never get it back in shape.

The best option with any chance of saving most of the installation would probably be a giant airbag with enough helium bladders to make it near neutrally buoyant, winched into place under the platform, and lots of smaller airbags under the middle of the dish emplaced by ROVs and inflated till the radial cables were slack enough not to whiplash.

Emplacing the cutting charges on the platform cables would be challenging using aerial ROVs, but if you have that capability, attaching support lines to the main cables sufficient to stop them falling on the dish would also be possible.
 

Offline CatalinaWOW

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Re: The end of the line for the Arecibo radio telescope
« Reply #38 on: November 28, 2020, 04:03:10 am »
If we really like the idea of Arecibo we should start surveying where we want to put its replacement, and designing what it should look like.  The existing site might be the answer, in which case figuring out how best to demolish/salvage the existing structure to make way for the future makes sense.  Otherwise it becomes just another one of those pitch experiments where it might be days or decades before the final failure occurs.
 

Online coppercone2

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Re: The end of the line for the Arecibo radio telescope
« Reply #39 on: November 28, 2020, 04:14:07 am »
hanging something on it like a chirstmas ornament is much easier then trying to grip cables in any way to support 900 tons even if distributed

can you totally blow that thing to smithereens so it does not destroy the stuff it lands on (really really big boom)? if you can turn it into pop corn. practice for asteroids

you can evacuate the surrounding area and try to blow it up so it goes outwards like a fountain and away from the crater.

this comes to mind, but I am not sure how well it will work on aluminum, but I think if its all bolted together its possible to set it up so it does (I think that is a bangalor pipe filled with explosives). Put a bunch of sticks like that in the shape of a 3d * and it might work? That thing got vaporized. You would need to use shattering explosives (military) not common nice demolition explosives. You could build a replica to test it first on a tower to make sure it is sufficiently disintegrated.


« Last Edit: November 28, 2020, 04:32:14 am by coppercone2 »
 

Offline magic

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Re: The end of the line for the Arecibo radio telescope
« Reply #40 on: November 28, 2020, 08:31:14 am »
I don't understand how it got THAT bad without anyone noticing that failure was imminent. Rust of cables like that doesn't happen overnight. At least it isn't just in my country that so many people defer maintenance until it becomes a huge expensive problem. I know multiple people who kept putting off having the timing belt on their car engine changed until it snapped and destroyed the engine. People do the same thing with oil changes.
It's called fall of civilization and poverty.

But when I say it they don't listen because they have the latest generation iShiny to distract themselves with :horse:
Oh, and big dreams. Never forget big dreams ::)
 

Offline CJay

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Re: The end of the line for the Arecibo radio telescope
« Reply #41 on: November 28, 2020, 10:36:16 am »
The strands were broken from the two recent overload events.

Sorry for lack of a link, but somewhere in the various videos I've watched about this recently there was a short sequence of pictures of the cables, taken by drones.

I'd think even controlled demolition by placing cutting charges on all the cables so they can be dropped in one go, would be an extremely dangerous job.

I think maybe you've answered the question of how to place demolition charges, I wonder if it would be possible to have drones place shaped charges, one packaged so it 'falls' into correct alignment to cut the cable...
 

Offline CatalinaWOW

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Re: The end of the line for the Arecibo radio telescope
« Reply #42 on: November 28, 2020, 04:39:05 pm »
I don't understand how it got THAT bad without anyone noticing that failure was imminent. Rust of cables like that doesn't happen overnight. At least it isn't just in my country that so many people defer maintenance until it becomes a huge expensive problem. I know multiple people who kept putting off having the timing belt on their car engine changed until it snapped and destroyed the engine. People do the same thing with oil changes.

Yeah, but this was our country.  Puerto Rico isn't a state, but for all practical purposes it is part of the US.  And the folk who provide funding and deferred maintenance were virtually all in the mainland. 

This died because it was less important to us than the military, the ISS, school lunches student loans and a myriad of other things, many of which no one really cares about.
 

Offline james_s

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Re: The end of the line for the Arecibo radio telescope
« Reply #43 on: November 28, 2020, 06:55:40 pm »
Oh I missed that it's Puerto Rico, for some reason I was thinking it was somewhere in South America. Figures. So typically American to neglect modest repairs until it turns into a huge expensive writeoff.
 

Offline David Hess

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Re: The end of the line for the Arecibo radio telescope
« Reply #44 on: November 29, 2020, 09:27:31 pm »
I don't understand how it got THAT bad without anyone noticing that failure was imminent. Rust of cables like that doesn't happen overnight. At least it isn't just in my country that so many people defer maintenance until it becomes a huge expensive problem. I know multiple people who kept putting off having the timing belt on their car engine changed until it snapped and destroyed the engine. People do the same thing with oil changes.

Maintenance was limited (halted?) by budget reductions after 2007 if not sooner.
 

Online Ian.M

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Re: The end of the line for the Arecibo radio telescope
« Reply #45 on: November 29, 2020, 09:37:58 pm »
All for want of a small team of high rope access trained riggers tasked to permanent maintenance, a magnetic wire rope tester and a few barrels of anhydrous lanolin per annum!  |O

The average wage in Puerto Rico is about 20K USD per annum and there's historically in excess of 10% unemployment, so I bet the cables could have been kept greased (against rust) and inspected for appox. 100K USD per annum budget.  If you cant raise >$20 per hour above base access costs from selling access time on one of the largest radio telescope dishes in the world to fund routine maintenance, then your management team is criminally incompetent.  :horse:
« Last Edit: November 29, 2020, 09:57:13 pm by Ian.M »
 
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Online coppercone2

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Re: The end of the line for the Arecibo radio telescope
« Reply #46 on: November 29, 2020, 11:21:09 pm »
management: what do we need that thing again for? (asks same question every year)
 

Online nfmax

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Offline MadTux

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Re: The end of the line for the Arecibo radio telescope
« Reply #48 on: December 01, 2020, 04:37:10 pm »
Sad  :-[
 
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Offline CatalinaWOW

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Re: The end of the line for the Arecibo radio telescope
« Reply #49 on: December 01, 2020, 04:37:35 pm »
That certainly validates the risk assessment.  Too bad they didn't use those same skills when allocating maintenance funds.
 


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