mersenneforum.org Arecibo's demise and possible rebuild.
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 2020-11-23, 21:25 #23 firejuggler     Apr 2010 Over the rainbow 2·5·11·23 Posts Plus, as Puerto ricco has no representation in the senate (? ) it is not like they got any money.
2020-11-23, 21:25   #24
Dr Sardonicus

Feb 2017
Nowhere

10F916 Posts

Quote:
 Originally Posted by Uncwilly The thing suspended in the centre weighs ~900 tons. There is concern based upon examination of the cables that remain, that one or more could give way suddenly. 2 of the 3 firms asked to examine it say that there is not a safe way forward to stabilize it and continue using it. They are recommending explosively severing all of the lines at once. Dropping all of that into the dish will cause much damage to the dish.
Seems about the only reasonably safe way. At Telescope Description | The Arecibo Observatory we find (my emphasis, just to get the size of things):

Quote:
 Suspended 450 feet above the reflector is the 900 ton platform. Similar in design to a bridge, it hangs in midair on eighteen cables, which are strung from three reinforced concrete towers. One is 365 feet high, and the other two are 265 feet high. All three tops are at the same elevation. The combined volume of reinforced concrete in all three towers is 9,100 cubic yards. Each tower is back-guyed to ground anchors with seven 3.25 inch diameter steel bridge cables. Another system of three pairs of cables runs from each corner of the platform to large concrete blocks under the reflector. They are attached to giant jacks which allow adjustment of the height of each corner with millimeter precision. Just below the triangular frame of the upper platform is a circular track on which the azimuth arm turns. The azimuth arm is a bow shaped structure 328 feet long. The curved part of the arm is another track, on which a carriage house on one side and the gregorian dome (installed in 1996) on the other side can be positioned anywhere up to twenty degrees from the vertical.
Let's see. 900 tons hanging 450 feet above the reflector. OK, cut all the platform's suspension cables simultaneously. About five seconds later... Impact! The reflector is supported by a cradle of steel cables. If enough of them snap or are ripped from their moorings, the whole reflector might wind up at the bottom of the hole. Even if it doesn't, it would be be a heck of a job trying to clear the rubble if you wanted to start over.

2020-11-24, 13:42   #25
rudy235

Jun 2015
Vallejo, CA/.

7×139 Posts

Found this.
Arecibo observatory supporters ask White House to help save damaged radio telescope

https://www.space.com/arecibo-observ...ng-white-house

Quote:
 That shutdown was averted; in 2017, the NSF decided to develop partnerships that would flesh out the observatory's operating costs. But that situation became less tenable for the agency earlier this month. Just as observatory personnel were preparing to begin repairs after a cable supporting the 900-ton science platform slipped out of its socket in August, a second cable connected to the same tower snapped unexpectedly on Nov. 6. From engineering analyses of the weakened telescope, the NSF concluded that the structure was too dangerous to attempt to repair and announced it would begin developing a plan to decommission the trailblazing instrument, which has been observing the heavens since the early 1960s. For Ruperto-Hernández, the announcement was devastating. "It's everything for me," he said. "Without it, I wouldn't be here, I wouldn't have the path that I'm on, I wouldn't have the opportunities that I've been presented."

2020-11-24, 16:08   #26
storm5510
Random Account

"Norman D. Powell"
Aug 2009
Indiana, USA.

111010110002 Posts

Quote:
 Originally Posted by Uncwilly The thing suspended in the centre weighs ~900 tons. There is concern based upon examination of the cables that remain, that one or more could give way suddenly. 2 of the 3 firms asked to examine it say that there is not a safe way forward to stabilize it and continue using it. They are recommending explosively severing all of the lines at once. Dropping all of that into the dish will cause much damage to the dish.
900 tons! Wow! The image I posted clearly makes it appear smaller that it actually is. What is the diameter of the dish?

2020-11-24, 16:17   #27
rudy235

Jun 2015
Vallejo, CA/.

7×139 Posts

Quote:
 Originally Posted by storm5510 900 tons! Wow! The image I posted clearly makes it appear smaller that it actually is. What is the diameter of the dish?
305 metres aka 1000 feet.

2020-11-24, 16:17   #28
Uncwilly
6809 > 6502

"""""""""""""""""""
Aug 2003
101×103 Posts

24A716 Posts

Quote:
 Originally Posted by storm5510 900 tons! Wow! The image I posted clearly makes it appear smaller that it actually is. What is the diameter of the dish?
Watch the video that I linked to.
Duckduckgo is your friend.

2020-11-24, 17:59   #29
Dr Sardonicus

Feb 2017
Nowhere

10000111110012 Posts

The Arecibo Observatory Telescope Description site I gave a link to a few posts back says
Quote:
 Those who see the Arecibo radio telescope for the first time are astounded by the enormousness of the reflecting surface, or radio mirror. The huge "dish" is 305 m (1000 feet) in diameter, 167 feet deep, and covers an area of about twenty acres. The surface is made of almost 40,000 perforated aluminum panels, each measuring about 3 feet by 6 feet, supported by a network of steel cables strung across the underlying karst sinkhole. It is a spherical (not parabolic) reflector.
The main site The Arecibo Observatory | Research center operated by UCF, YEI &amp; UMET and funded by NSF and NASA has a long list of the Observatory's capabilities and accomplishments.

The R's have a couple of ways to spin this that are obvious to me. One, they can say good riddance to something that was a huge drain of taxpayer dollars on studying space, when we have problems right here on Earth to worry about. Or, two, they could blame the loss of a national treasure on the Democrats generally, and, assuming the demolition begins during Joe Biden's term of office, on him particularly. Scratch that assumption, in this scenario they'll blame him (and the Democrats) anyway.

2020-11-24, 18:11   #30
storm5510
Random Account

"Norman D. Powell"
Aug 2009
Indiana, USA.

23×5×47 Posts

Quote:
 Originally Posted by rudy235 305 metres aka 1000 feet.

If the dish was flat, a person could lay down two Saturn V rockets and two Saturn 1B rockets, end-to-end, and only exceed the diameter by roughly two meters. In that area, anyway. I would never have though it was this large by just looking at a photo.

 2020-11-24, 18:45 #31 firejuggler     Apr 2010 Over the rainbow 2·5·11·23 Posts I seem to have read somewhere that the budget for the maintenance of the telescope have been cut from 12M$to 2M$ a year , some time ago. You get what you pay for. Last fiddled with by firejuggler on 2020-11-24 at 18:45
2020-11-24, 19:13   #32
Dr Sardonicus

Feb 2017
Nowhere

434510 Posts

Quote:
 Originally Posted by storm5510 I would never have though it was this large by just looking at a photo.
... Unless, perhaps, you realized that in that photo you posted, those tiny little green things around the edges of the dish are trees...

2020-11-25, 01:26   #33
kriesel

"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest

22×32×137 Posts

Quote:
 Originally Posted by storm5510 If the dish was flat, a person could lay down two Saturn V rockets and two Saturn 1B rockets, end-to-end, and only exceed the diameter by roughly two meters.
Tuck the nose cone tip of one into an engine nozzle of the next, to accommodate a few otherwise excess meters. https://en.wikipedia.org/wiki/Rocketdyne_F-1
https://en.wikipedia.org/wiki/Rocketdyne_H-1

Last fiddled with by kriesel on 2020-11-25 at 01:35

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