On December 1, 2020, Puerto Ricans and the scientific community received the unfortunate news of the collapse of the rArecibo adiotelescope. After six decades of contributions to the study of space, his impressive legacy culminated when several of the cables used to suspend the transmitters above the reflector dish gave way. This caused a chain reaction that caused the towers to which the cables were anchored to collapse; The debris destroyed a good part of the reflector dish.
Four years later, a new report prepared by him Committee for Analysis of the Causes of the Failure and Collapse of the 305-meter Telescope of the Arecibo Observatory and published by the organization National Academies of Sciences, Engineering and Medicine (National Academies), details the causes that led to the collapse of what was, until 2021, the largest reflector dish in the world.
According to the Committee, The fundamental cause of the collapse was a long-term, “unprecedented and accelerated” failure, induced by the deterioration of the zinc with which the fasteners of the support cables of the instruments suspended above the plate were molded.
“In more than a century of use of this type of fasteners, all forensic investigations agreed that a failure like that had never been reported,” reads the report, highlighting that zinc fasteners are indicated for the type of fastener. Puerto Rico’s tropical climate and for the constant weight they would support.
Zinc is a metal that, when exposed to moisture, creates an oxide layer that protects it from corrosion. Being a metal that is highly resistant to corrosion, it is usually used to create covers that are placed on other metals that are more susceptible to corrosion, such as steel.
“The only hypothesis that the Committee was able to develop, and which provides a plausible, although unprovable, answer to the observed failure pattern, is that the degradation of the zinc in the fasteners was unexpectedly accelerated in the exceptionally powerful electromagnetic radiation environment of the Arecibo telescope. ”, The Committee maintained in what they described as a diagnosis by exclusion, after analyzing research carried out by the University of Central Florida, administrator of the observatory, and by the National Science Foundation (NSF), federal agency that provides funds for the operation of the facility.
In other words, The committee understands that electrical discharges during the use of the observatory’s transmitters reached the cables and zinc covers for decades, which accelerated the degradation of the fasteners through a process known as electroplasticity.
In simple words, electroplasticity is a phenomenon in which the properties of a material (such as plastic or metals) change as an electric current is applied to it. In the case of the Arecibo radio telescope, the committee understands that the currents received by the suspension cables during normal operations of the radio telescope gradually accelerated the degradation of the zinc used to mold the fasteners, which probably caused them to give way. his grip on the cables.
In the report, the Committee stressed that zinc is a material that is used to create roofing due to its low melting point (the minimum temperature for a solid material to pass into a liquid state) and its resistance to corrosion, so concluded that the failure of the radio telescope fasteners “was not due to poor materials or workmanship”.
The researchers, likewise, determined that the beginning of the failure sequence probably began after the passage of the Hurricane Mariain September 2017, since, according to the report, signs of cable detachment were minimal before the cyclone.
“Maria subjected the Arecibo telescope to winds of between 105 and 118 miles per hour”details the investigation.
However, a forensic structural analysis after María established that “the hurricane’s winds should not have damaged the telescope’s cable structure, or caused any other cables to detach from its cover.”
Even so, the Committee noted that inspections carried out in late 2018 and early 2019 revealed “cable detachment (cables loose) greater than 1.5 inches in the auxiliary fasteners,” despite the fact that, before Maria’s impact, “the information collected “He pointed out that the cable release was half an inch.”
“After Maria, the Arecibo telescope warned that its structure was in danger due to the increase in cables coming loose. The documented lack of concern from the contracted engineers regarding the cable issue or safety factors between Hurricane Maria in 2017 and the collapse is alarming,” the researchers highlighted.
The scientists highlighted that the degradation of zinc would have continued regardless of the hurricane. However, they noted that, although the additional tension applied to the cables was well below the force required to produce a detachment, “this relatively small increase appears to have significantly aggravated the degradation of the covers.”
Given these findings, the Committee recommended that the NSF hand over the remaining fasteners and cables recovered after the collapse for further investigation by the scientific community. Likewise, he highlighted that the radio telescope operators would have benefited from more detailed guidance on engineering or structural risks in relation to the inspection protocol, documentation and indicators of structural deterioration.
An icon of science
The radio telescope consisted of a 1,000-foot-diameter reflector dish and a 900-ton Gregorian dome, or instrument platform, hanging 450 feet high.. It was the largest in the world until it was dethroned, in 2016, by the FAST radio telescope in China, whose reflector boasts a diameter of 1,640 feet.
Some of the contributions of the radio telescope to astronomy include discover the speed of rotation of Mercuryin 1967, and the first binary pulsar, in 1974. In 1992, the facility discovered the first exoplanets around the pulsar PSR 1257+12, and in 2016 it was the first to detect a fast radio burst (FRB).
The instrument was also used to send, on November 16, 1974, the “Arecibo Message”, the most powerful emission ever sent to space. The transmission, broadcast to the Messier 13 globular cluster, was a demonstration of human technological knowledge in which a coded message was transmitted containing the numbers one to 10, the atomic numbers of the elements that make up human DNA, the formulas of the chemical compounds that make up DNA nucleotides, the estimated number of nucleotides in human DNA and a graphical representation of DNA, the average height of a human being along with the total global population in 1974, a graphical representation of our system solar, and a graphic representation of the Arecibo radio telescope.
Since 2006, the NSF showed its first intention to close the radio telescope. In 2016 he tried again, but was unsuccessful thanks to public pressure. The reason behind the forced closure sought by the foundation was the expensive budget of the radio telescope, which was around $12 million annually.
The platform, which was property managed by the NSF, remained suspended by support cables connected to three towers. Precisely, two of these cables collapsed, on August 10 and November 6, 2020, compromising the stability of the structure.
The NSF then decided that it would dismantle the facility with the goal of repairing it. However, the structure unexpectedly collapsed before they executed that plan.
In September 2023, the NSF advertisement that four institutions were selected to operate the new Arecibo Observatory educational center that will open again in 2025, under the name “Arecibo Center for Culturally Relevant and Inclusive Science Education, Computational Skills and Community Engagement” (NSF Arecibo C3).
Initially, it was going to reopen in November of this year. However, according to the NSF, its opening was postponed due to several factors, including delays in transporting essential equipment to Puerto Rico and ongoing efforts to ensure the facility meets required access and inclusion standards.