Arecibo telescope collapsed because of a surprising engineering failure that inspections still should have spotted
According to a new very detailed engineering analysis into the causes of the collapse of the Arecibo radio telescope in Puerto Rico in 2020, the failure was caused first by a surprising interaction between the radio electronics of Arecibo and the traditional methods used to anchor the cables, and second by a failure of inspections to spot the problem as it became obvious.
The surprising engineering discovery is illustrated to the right, taken from figure 2-6 of the report. The main antenna of Arecibo was suspended above the bowl below by three main cables. The figure shows the basic design of the system used to anchor the cable ends to their sockets. The end of the cable bunches would be inserted into the socket, spread apart, and then zinc would be poured in to fill the gap and then act as a plug and glue to hold the cables in place. According to the report, this system has been used for decades in many applications very successfully.
What the report found however was at Arecibo over time the cable bunch and zinc plug slowly began to pull out of the socket, what the report labels as “zinc creep.” This was noted by inspectors, but dismissed as a concern because they still believed the engineering margins were still high enough to prevent failure at this point. In fact, this is exactly where the structure failed in 2020, with the first cable separating as shown in August 2020. The second cable did so in a similar manner in November 2020.
The report concluded that 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 report however also notes that the regular engineering inspections of the telescope had spotted this creep, which was clearly unusual and steadily becoming significant, and did not take action to address the issue when it should have. It also noted the slow response of the bureaucracy, not only to the damage caused earlier to the facility by Hurriane Maria in 2017, but to obtaining the funding for any repairs.
Ray Lugo [the principal investigator for Arecibo] described to the committee how months of his time during 2018 were spent writing, resubmitting, and justifying repair funding proposals. Repairs had to go through the traditional “bid and proposal” process, described in more detail below, which added years of delay.
We can forgive the inspectors somewhat for not noting the creep when they should, as its cause appears to be very unusual, still uncertain and rare, but the red tape that prevented proper and quick repair effort after the hurricane is shameful. Had the telescope gotten the proper support on time, the creep itself might have even been addressed, because the resources would have been there to deal with it.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
According to a new very detailed engineering analysis into the causes of the collapse of the Arecibo radio telescope in Puerto Rico in 2020, the failure was caused first by a surprising interaction between the radio electronics of Arecibo and the traditional methods used to anchor the cables, and second by a failure of inspections to spot the problem as it became obvious.
The surprising engineering discovery is illustrated to the right, taken from figure 2-6 of the report. The main antenna of Arecibo was suspended above the bowl below by three main cables. The figure shows the basic design of the system used to anchor the cable ends to their sockets. The end of the cable bunches would be inserted into the socket, spread apart, and then zinc would be poured in to fill the gap and then act as a plug and glue to hold the cables in place. According to the report, this system has been used for decades in many applications very successfully.
What the report found however was at Arecibo over time the cable bunch and zinc plug slowly began to pull out of the socket, what the report labels as “zinc creep.” This was noted by inspectors, but dismissed as a concern because they still believed the engineering margins were still high enough to prevent failure at this point. In fact, this is exactly where the structure failed in 2020, with the first cable separating as shown in August 2020. The second cable did so in a similar manner in November 2020.
The report concluded that 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 report however also notes that the regular engineering inspections of the telescope had spotted this creep, which was clearly unusual and steadily becoming significant, and did not take action to address the issue when it should have. It also noted the slow response of the bureaucracy, not only to the damage caused earlier to the facility by Hurriane Maria in 2017, but to obtaining the funding for any repairs.
Ray Lugo [the principal investigator for Arecibo] described to the committee how months of his time during 2018 were spent writing, resubmitting, and justifying repair funding proposals. Repairs had to go through the traditional “bid and proposal” process, described in more detail below, which added years of delay.
We can forgive the inspectors somewhat for not noting the creep when they should, as its cause appears to be very unusual, still uncertain and rare, but the red tape that prevented proper and quick repair effort after the hurricane is shameful. Had the telescope gotten the proper support on time, the creep itself might have even been addressed, because the resources would have been there to deal with it.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Minor edit in title: “a surprising”
Andi: Fixed. Thank you.
I see an analogy to state-run healthcare service bureaucracies in many countries. Even with an accurate diagnosis, waiting times for actual treatment cause many to die while awaiting service.
… the most powerful radio transmitter on Earth.
Was Arecibo typically or frequently used as a transmitter? One would think that, as a radio telescope, it would be relatively passively receiving signals from across vast distances—ergo, exceedingly weak signals, despite the dish gathering over a wide area. (I do remember hearing that a signal was transmitted across interstellar space decades ago from Arecibo. I suppose transmitting from Arecibo was done for radar investigation of asteroids, and the like.)
To Mr. Eagleson,
The HMO mess wasn’t much prettier.
Meteor Crater Arizona is where a replacement needs to be built.
Boneyards are in the desert for a reason.
@Michael McNeil I know it was used for radar astronomy too (actively transmitting signals and listening for reflections), looking for near earth objects and other things in the solar system.