Blame It On The Sockets: Forensic Analysis Of The Arecibo Collapse

August 29, 2023 by Dan Maloney 58 Comments

Nearly three years after the rapid unplanned disassembly of the Arecibo radio telescope, we finally have a culprit in the collapse: bad sockets.

In case you somehow missed it, back in 2020 we started getting ominous reports that the cables supporting the 900-ton instrument platform above the 300-meter primary reflector of what was at the time the world’s largest radio telescope were slowly coming undone. From the first sign of problems in August, when the first broken cable smashed a hole in the reflector, to the failure of a second cable in November, it surely seemed like Arecibo’s days were numbered, and that it would fall victim to all the other bad luck we seemed to be rapidly accruing in that fateful year. The inevitable finally happened on December 1, when over-stressed cables on support tower four finally gave way, sending the platform on a graceful swing into the side of the natural depression that cradled the reflector, damaging the telescope beyond all hope of repair.

The long run-up to the telescope’s final act had a silver lining in that it provided engineers and scientists with a chance to carefully observe the failure in real-time. So there was no real mystery as to what happened, at least from a big-picture perspective. But one always wants to know the fine-scale details of such failures, a task which fell to forensic investigation firm Thornton Tomasetti. They enlisted the help of the Columbia University Strength of Materials lab, which sent pieces of the failed cable to the Oak Ridge National Laboratory’s High Flux Isotope reactor for neutron imaging, which is like an X-ray study but uses streams of neutrons that interact with the material’s nuclei rather than their electrons.

The full report (PDF) reveals five proximate causes for the collapse, chief of which is “[T]he manual and inconsistent splay of the wires during cable socketing,” which we take to mean that the individual strands of the cables were not spread out correctly before the molten zinc “spelter socket” was molded around them. The resulting shear stress caused the zinc to slowly flow around the cable strands, letting them slip out of the surrounding steel socket and — well, you can watch the rest below for yourself.

As is usually the case with such failures, there are multiple causes, all of which are covered in the 300+ page report. But being able to pin the bulk of the failure on a single, easily understood — and easily addressed — defect is comforting, in a way. It’s cold comfort to astronomers and Arecibo staff, perhaps, but at least it’s a lesson that might prevent future failures of cable-supported structures.

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Hackaday Links: December 6, 2020

December 6, 2020 by Dan Maloney 4 Comments

By now you’ve no doubt heard of the sudden but not unexpected demise of the iconic Arecibo radio telescope in Puerto Rico. We have been covering the agonizing end of Arecibo from almost the moment the first cable broke in August to a eulogy, and most recently its final catastrophic collapse this week. That last article contained amazing video of the final collapse, including up-close and personal drone shots of the cable breaking. For a more in-depth analysis of the collapse, it’s hard to beat Scott Manley’s frame-by-frame analysis, which really goes into detail about what happened. Seeing the paint spalling off the cables as they stretch and distort under loads far greater than they were designed for is both terrifying and fascinating.

Exciting news from Australia as the sample return capsule from JAXA’s Hayabusa2 asteroid explorer returned safely to Earth Saturday. We covered Hayabusa2 in our roundup of extraterrestrial excavations a while back, describing how it used both a tantalum bullet and a shaped-charge penetrator to blast regolith from the surface of asteroid 162173 Ryugu. Samples of the debris were hoovered up and hermetically sealed for the long ride back to Earth, which culminated in the fiery re-entry and safe landing in the midst of the Australian outback. Planetary scientists are no doubt eager to get a look inside the capsule and analyze the precious milligrams of space dust. In the meantime, Hayabusa2, with 66 kilograms of propellant remaining, is off on an extended mission to visit more asteroids for the next eleven years or so.

The 2020 Remoticon has been wrapped up for most of a month now, but one thing we noticed was how much everyone seemed to like the Friday evening Bring-a-Hack event that was hosted on Remo. To kind of keep that meetup momentum going and to help everyone slide into the holiday season with a little more cheer, we’re putting together a “Holiday with Hackaday & Tindie” meetup on Tuesday, December 15 at noon Pacific time. The details haven’t been shared yet, but our guess is that this will certainly be a “bring-a-hack friendly” event. We’ll share more details when we get them this week, but for now, hop over to the Remo event page and reserve your spot.

On the Buzzword Bingo scorecard, “Artificial Intelligence” is a square that can almost be checked off by default these days, as companies rush to stretch the definition of the term to fit almost every product in the neverending search for market share. But even those products that actually have machine learning built into them are only as good as the data sets used to train them. That can be a problem for voice-recognition systems; while there are massive databases of utterances in just about every language, the likes of Amazon and Google aren’t too willing to share what they’ve leveraged from their smart speaker using customer base. What’s the little person to do? Perhaps the People’s Speech database will help. Part of the MLCommons project, it has 86,000 hours of speech data, mostly derived from audiobooks, a clever source indeed since the speech and the text can be easily aligned. The database also pulls audio and the corresponding text from Wikipedia and other random sources around the web. It’s a small dataset, to be sure, but it’s a start.

And finally, divers in the Baltic Sea have dredged up a bit of treasure: a Nazi Enigma machine. Divers in Gelting Bay near the border of Germany and Denmark found what appeared to be an old typewriter caught in one of the abandoned fishing nets they were searching for. When they realized what it was — even crusted in 80-years-worth of corrosion and muck some keys still look like they’re brand new — they called in archaeologists to take over recovery. Gelting Bay was the scene of a mass scuttling of U-boats in the final days of World War II, so this Engima may have been pitched overboard before by a Nazi commander before pulling the plug on his boat. It’ll take years to restore, but it’ll be quite a museum piece when it’s done.

NSF Releases Video Of Arecibo’s Final Moments

December 3, 2020 by Tom Nardi 82 Comments

Today the National Science Foundation released a pair of videos that document the collapse of the Arecibo Observatory with incredible detail. A wide shot, apparently taken from the Visitors Center, shows the 900 ton instrument platform breaking free and swinging on the remaining support cables until it smashes into the edge of the dish. The second clip, recorded by an airborne drone, is focused directly on the cables as they failed. Both can be seen in the video embedded below.

Together, they produce an invaluable visual record of what finally brought the iconic radio telescope down. As was predicted by engineers earlier in the month, the failure of another support cable on tower 4 triggered a chain reaction that brought the entire platform crashing down onto the 305 meter reflector. Footage from a drone observing the top of tower 4 shows that the entire sequence, from the first visual wire break to the remaining cables being torn from their mounts, only took five seconds. While some initially doubted the NSF’s determination that it was too dangerous to repair Arecibo, this footage seems to prove just how tenuous the structural integrity of the Observatory really was.

A drone captured the critical cable failure.

These videos will hopefully help investigators who still need to determine why the cables failed in the first place. The cable in August didn’t snap, it simply pulled lose from its mount. It was suspected that the cable may have been incorrectly installed, but as it was only a backup, the situation was not seen as critical. But when the second cable failed in November it was found to have snapped at just 60% of its minimum breaking strength.

This immediately called into question the condition of the remaining cables, and ultimately lead to the decision by the NSF to proceed with a controlled demolition of the Observatory that would preserve as much of the scientific equipment as possible. Unfortunately, the remaining cables didn’t last long enough to put that plan into action.

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The Battle For Arecibo Has Been Lost

November 19, 2020 by Tom Nardi 98 Comments

It is with a heavy heart that we must report the National Science Foundation (NSF) has decided to dismantle the Arecibo Observatory. Following the failure of two support cables, engineers have determined the structure is on the verge of collapse and that the necessary repairs would be too expensive and dangerous to conduct. At the same time, allowing the structure to collapse on its own would endanger nearby facilities and surely destroy the valuable research equipment suspended high above the 300 meter dish. Through controlled demolition, the NSF hopes to preserve as much of the facility and its hardware as possible.

When the first support cable broke free back in August, we worried about what it meant for the future of this unique astronomical observatory. Brought online in 1963 as part of a Cold War project to study how ICBMs behaved in Earth’s upper atmosphere, the massive radio telescope is unique in that it has the ability to transmit as well as receive. This capability has been used to produce radar maps of distant celestial objects and detect potentially hazardous near-Earth asteroids.

In 1974, it was even used to broadcast the goodwill of humankind to any intelligent lifeforms that might be listening. Known as the “Arecibo Message”, the transmission can be decoded to reveal an assortment of pictograms that convey everything from the atomic numbers of common elements to the shape of the human body. The final icon in the series was a simple diagram of Arecibo itself, so that anyone who intercepted the message would have an idea of how such a relatively primitive species had managed to reach out and touch the stars.

There is no replacement for the Arecibo Observatory, nor is there likely to be one in the near future. The Five hundred meter Aperture Spherical Telescope (FAST) in China is larger than Arecibo, but doesn’t have the crucial transmission capability. The Goldstone Deep Space Communications Complex in California can transmit, but as it’s primarily concerned with communicating with distant spacecraft, there’s little free time to engage in scientific observations. Even when it’s available for research, the largest dish in the Goldstone array is only 1/4 the diameter of the reflector at Arecibo.

Just last week we wondered aloud whether a nearly 60 year old radio telescope was still worth saving given the incredible advancements in technology that have been made in the intervening years. Now, unfortunately, we have our answer.

What Is Worth Saving?

November 14, 2020 by Elliot Williams 72 Comments

When it rain, it pours. One of the primary support cables holding up the Arecibo Observatory dish in Puerto Rico has just snapped, leaving its already uncertain fate. It had been badly damaged by Hurricane Maria in 2017, and after a few years of fundraising, the repairs were just about to begin on fixing up that damage, when the cable broke. Because the remaining cables are now holding increased weight, humans aren’t allowed to work on the dome until the risk of catastrophic failure has been ruled out — they’re doing inspection by drone.

Arecibo Observatory has had quite a run. It started out life as part of a Cold War era ICBM-tracking radar, which explains why it can transmit as well as receive. And it was the largest transmitting dish the world had. It was used in SETI, provided the first clues of gravitational waves, and found the first repeating fast radio bursts. Its radar capabilities mean that it could be used in asteroid detection. There are a number of reasons, not the least of which its historic import, to keep it running.

So when we ran this story, many commenters, fearing the worst, wrote in with their condolences. But some wrote in with outrage at the possibility that it might not be repaired. The usual suspects popped up: failure to spend enough on science, or on infrastructure. From the sidelines, however, and probably until further structural studies are done, we have no idea how much a repair of Arecibo will cost. After that, we have to decide if it’s worth it.

Per a 2018 grant, the NSF was splitting the $20 M repair and maintenance bill with a consortium led by the University of Central Florida that will administer the site. With further damage, that might be an underestimate, but we don’t know how much of one yet.

When do you decide to pull the plug on something like this? Although the biggest, Arecibo isn’t the only transmitter out there. The next largest transmitters are part of Deep Space Network, though, and are busy keeping touch with spacecraft all around our solar system. For pure receiving, China’s FAST is bigger and better. And certainly, we’ve learned a lot about radio telescopes since Arecibo was designed.

I’m not saying that we won’t shed a tear if Arecibo doesn’t get repaired, but it’s not the case that the NSF’s budget has been hit dramatically, or that they’re unaware of the comparative value of various big-ticket astronomy projects. Without being in their shoes, and having read through the thousands of competing grant proposals, it’s hard to say that the money spent to prop up a 70 year old telescope wouldn’t be better spent on something else.

Tensions High After Second Failed Cable At Arecibo

November 11, 2020 by Tom Nardi 45 Comments

Today we’re sad to report that one of the primary support cables at the Arecibo Observatory has snapped, nudging the troubled radio telescope closer to a potential disaster. The Observatory’s 300 meter reflector dish was already badly in need of repairs after spending 60 years exposed to the elements in Puerto Rico, but dwindling funds have made it difficult for engineers to keep up. Damage from 2017’s Hurricane Maria was still being repaired when a secondary support cable broke free and smashed through the dish back in August, leading to grave concerns over how much more abuse the structure can take before a catastrophic failure is inevitable.

The situation is particularly dire because both of the failed cables were attached to the same tower. Each of the remaining cables is now supporting more weight than ever before, increasing the likelihood of another failure. Unless engineers can support the dish and ease the stress on these cables, the entire structure could be brought down by a domino effect; with each cable snapping in succession as the demands on them become too great.

Workers installing the reflector’s mesh panels in 1963.

As a precaution the site has been closed to all non-essential personnel, and to limit the risk to workers, drones are being used to evaluate the dish and cabling as engineers formulate plans to stabilize the structure until replacement cables arrive. Fortunately, they have something of a head start.

Back in September the University of Central Florida, which manages the Arecibo Observatory, contacted several firms to strategize ways they could address the previously failed cable and the damage it caused. Those plans have now been pushed up in response to this latest setback.

Unfortunately, there’s still a question of funding. There were fears that the Observatory would have to be shuttered after Hurricane Maria hit simply because there wasn’t enough money in the budget to perform the relatively minor repairs necessary. The University of Central Florida stepped in and provided the funding necessary to keep the Observatory online in 2018, but they may need to lean on their partner the National Science Foundation to help cover the repair bill they’ve run up since then.

The Arecibo Observatory is a unique installation, and its destruction would be an incredible blow for the scientific community. Researchers were already struggling with the prospect of repairs putting the powerful radio telescope out of commission for a year or more, but now it seems there’s a very real possibility the Observatory may be lost. Here’s hoping that teams on the ground can safely stabilize the iconic instrument so it can continue exploring deep space for years to come.

Damage To Arecibo Leaves Gaping Hole In Astronomy

August 24, 2020 by Tom Nardi 69 Comments

In the early morning hours of August 10th, a support cable at the Arecibo Observatory pulled lose from its mount and crashed through the face of the primary reflector below. Images taken from below the iconic 305 meter dish, made famous by films such as Contact and GoldenEye, show an incredible amount of damage. The section of thick cable, estimated to weigh in at around 6,000 kilograms (13,000 pounds), had little difficulty tearing through the reflector’s thin mesh construction.

Worse still, the cable also struck the so-called “Gregorian dome”, the structure suspended over the dish where the sensitive instruments are mounted. At the time of this writing it’s still unclear as to whether or not any of that instrumentation has been damaged, though NASA at least has said that the equipment they operate inside the dome appears to have survived unscathed. At the very least, the damage to the dome structure itself will need to be addressed before the Observatory can resume normal operations.

The Arecibo Observatory by JidoBG [CC-BY-SA 4.0]

But how long will the repairs take, and who’s going to pay for them? It’s no secret that funding for the 60 year old telescope has been difficult to come by since at least the early 2000s. The cost of repairing the relatively minor damage to the telescope sustained during Hurricane Maria in 2017 may have been enough to shutter the installation permanently if it hadn’t been for a consortium led by the University of Central Florida. They agreed to share the burden of operating the Observatory with the National Science Foundation and put up several million dollars of additional funding.

It’s far too early to know how much time and money it will take to get Arecibo Observatory back up to operational status, but with the current world situation, it seems likely the telescope will be out of commission for at least the rest of the year. Given the fact that repairs from the 2017 damage still haven’t been completed, perhaps even longer than that. In the meantime, astronomers around the globe are left without this wholly unique resource.

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