Failure analysis of the Arecibo 305 meter telescope collapse
nap.nationalacademies.org
nap.nationalacademies.org
All the reported experimental zinc electroplasticity (EP) data were developed at current densities orders of magnitude higher than those possibly present in the Arecibo Telescope but measured in laboratory experimental periods that were orders of magnitude shorter than the telescope's socket zinc service.
There are no reported experimental data concerning low-current, long-term EP, which the committee has lumped together under the term "LEP", affecting zinc's creep mechanisms over decades.
The timing and patterns of the Arecibo Telescope's socket failures make the LEP hypothesis the only one that the committee could find that could potentially explain the failure patterns observed.
Accelerated aging is, as far as I know, pretty much standard in the industry. Nobody can wait 20 years to find out if a certain material is good enough or not.
However, the real failure seems to be the lack of urgency when they signs started to show up:
Upon reflection, the unusually large and progressive cable pullouts of key structural cables that could be seen during visual inspection several months and years before the M4N failure should have raised the highest alarm level, requiring urgent action. The lack of documented concern from the contracted engineers about the inconsequentiality of the cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming.
This is crazy. Basically cables were pulling out for months and years and no one raised the alarm? In many industries that could be a criminal or career ending malpractice. Are the "contracted engineers" liable?
On Nov 19 2020, NPR was already reporting that "Sean Jones, Director for the Mathematical and Physical Sciences Directorate at the NSF, said the telescope will be dismantled. ... after receiving ... the engineering assessments, we have found no path forward that would allow us to do so safely..." https://www.npr.org/2020/11/19/936677582/world-renowned-arec...
In retrospect, it seems that, -at its age- the design got in the way of repairs. The scope made possible a lot of great finds in its day, but it'd become too weak to save.
I wouldn’t jump to the conclusion that the consulting engineer was incompetent. Sometimes a bureaucrat tells you to sharpen your pencils and come back with the answer That fits the budget they have if you want to keep your professional services contract going.
It seems unlikely that UCF had adequate time and resources to review and understand the Arecibo Telescope's original 1963 design, the 1974 upgrade, the structural inspection and maintenance records produced for nearly 50 years, [...] and the key factors, such as the wire breaks and cable pullout of the sockets and their significance on the strength and integrity of the structure.
The measured cable pullout may have appeared "normal" to [the UCF staff] and was not on their radar as signs of structural distress. The lack of concern may be because a small cable pullout was present from the beginning, and no one in authority had previously raised an alarm
But yeah, seems weird no-one of the contractors tried to raise an alarm.
Discontinuity could explain problems like this readily.
And what if they did? Then what? My guess is the conversation went something like this:
"Okay, cables are pulling out. Raising this issue will not magically make money appear to fix it as nobody wants to fund this. Tell me, how much do you like your job? If you flag this, you may lose your job directly and if the project gets shut down you may lose your job indirectly. So, how about we bury this as much as possible, cross our fingers and bank as much money as possible in the meantime, eh?"
The reliance by the consultants (before and after the first cable failure in 2020) on a perceived allowable pullout of one-sixth of the cable diameter, which should only be seen at loading at 80 percent of ultimate cable strength, does not align with the AASHTO M 277 standard guidance. The committee, therefore, disagrees with the suggestion made in the Thornton Tomasetti, Inc. (TT) 2022 report, Arecibo Telescope Collapse: Forensic Investigation,13 to use the D/6 limit as a threshold for slip monitoring.
And for most applications it was obsoleted by the larger new telescope in china, so there was no large push to turn that ship around from the wider scientific community.
Everyone working in large corporations knows this.
They're relatively new, they're relatively expensive (which saves them from being used in the worst of the applications) and like most things inherent to steel cable and whatnot they tend to get employed in situations where safety factors are generous. Don't count your chickens before they hatch.
I have a feeling such measurement and modelling might have been wrong.
It's easy to miss some oscillation mode, particularly high frequency longitudinal wave's in the cables, which couldn't be picked up by a laser survey due to the kilometers per second these waves travel.
You have a mechanical failure that can’t be seen in the labs and isn’t reproducible at other sites. Suggests something environmental.
Like when natural fiber army gear starts dissolving in the jungles of Vietnam.
Could be direct action, or a side effect of a chemical in plant or animal detritus. Like pigeon poop on car paint.
Active galvanic action will ruin your day.
Albeit having limited field of view the Arecibo Telescope was very sensitive[2], and so could see pulsars that the other telescopes they used could not. And the longer they could collect data from a set of pulsars the lower frequency waves they could probe.
[1]: https://nanograv.org/news/15yrRelease
[2]: https://pirsa.org/20100068 Moving Closer to a Detection of nHz-frequency Gravitational Waves with NANOGrav (Arecibo details at around 10:20)
https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Sp...
The uniqueness of Arecibo was this transmit coupled with such a large aperture (so small pattern on sky).
the Sun? that's something I never thought about, and now that I'm thinking about it, still seems very interesting. It seems like there would be so much noise radiating from the burning ball of fusion that radar signals would just get absorbed/lost. And now I've sat here for 5 minutes doing nothing but imagining this.
Although it's emission (due to the transparence of it) is not just a disk but sometimes increases on the limb depending on frequency, http://a.superkuh.com/solar-disk_relative-brightness_vs_sola...
Here's a diagram of how the ray paths from an Earth based radar reflect from the soft target that is the sun, http://a.superkuh.com/what-solar-radio-looks-like.jpg
>>> The only hypothesis the committee could develop that provides a plausible but unprovable answer to all these questions and the observed socket failure pattern is that the socket zinc creep was unexpectedly accelerated in the Arecibo Telescope's uniquely powerful electromagnetic radiation environment. The Arecibo Telescope cables were suspended across the beam of "the most powerful radio transmitter on Earth." The other investigations failed to note several failure patterns and provided no plausible explanation for most of them. To answer these questions with empirical evidence instead of only the inferences that can be made from the existing data, a more comprehensive and widespread forensic analysis of "good" and "bad" socket workmanship and the low-current, long-term effect on zinc creep is required.
It was both.
The Arecibo message was transmitted from there - https://en.wikipedia.org/wiki/Arecibo_message
> The entire message consisted of 1,679 binary digits, approximately 210 bytes, transmitted at a frequency of 2,380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 450 kW.
There's also the field of radar astronomy (not radio astronomy) https://en.wikipedia.org/wiki/Radar_astronomy where you bounce of a signal off of an object in the solar system (such as an asteroid)
> Radar provides the ability to study the shape, size and spin state of asteroids and comets from the ground. Radar imaging has produced images with up to 7.5-meter resolution. With sufficient data, the size, shape, spin and radar albedo of the target asteroids can be extracted.
> ...
> In August 2020 the Arecibo Observatory (Arecibo Planetary Radar) suffered a structural cable failure, leading to the collapse of the main telescope in December of that year.
> There is one remaining radar astronomy facility in regular use, the Goldstone Solar System Radar.
They might only know about Puerto Rico thus limiting themselves to just that.
Let's be clear, this is not decided by Puerto Ricans. Congress ultimately decides this. How they decide is up to them. Until now, they haven't done much.
Wasn't PR denied help with hurricane repair and rebuilding?
On the other hand, is there a perfect one?