Arecibo telescope failure analysis suggests radiation role • The Register

The collapse of the 305-meter telescope at Arecibo Observatory in 2020 is being attributed to zinc creep – slow deformation due to stress – in the telescope's cable spelter sockets, according to a committee report from the National Academies of Sciences, Engineering, and Medicine.

This effect may also have been accelerated by the effect of low-level electric current on the structure of zinc – a phenomenon known as electroplasticity.

Built in 1963, the iconic Puerto Rico-based telescope was the largest single-aperture device in the world until 2016 – when it was surpassed by China's Five-hundred-meter Aperture Spherical Telescope (FAST, or Tianyan). It contributed to numerous scientific discoveries, such as finding the first known binary pulsar.

When Hurricane Maria struck Puerto Rico in 2017, the telescope was damaged, but it remained operational until 2020 when a supporting cable broke from its socket and fell across the main dish. Repair efforts in November 2020 failed, and the National Science Foundation (NSF) decided to demolish the structure.

In its place, the NSF plans to open a science education facility next year: the NSF Arecibo Center for Culturally Relevant and Inclusive Science Education, Computational Skills, and Community Engagement (NSF Arecibo C3).

The committee report confirms prior findings by other groups, including NASA engineers, who attributed the failure in a 2021 forensic analysis to "progressive zinc extrusion on several Arecibo sockets, which in hindsight indicated significant cumulative damage."

But it also goes beyond prior analyses by proposing a hypothesis that attempts to address several unanswered questions. For instance, why did the telescope sockets and cables fail despite a safety factor above two – the ratio of cable strength to applied load? And why did these spelter sockets exhibit accelerated zinc creep when others have not over a century of socket use?

The National Academies investigators hypothesize that the failure was hastened by exposure to electromagnetic radiation.

"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 zinc socket creep was unexpectedly accelerated by the Arecibo Telescope's unique powerful electromagnetic radiation environment."

Prior reports, the committee wrote, failed to adequately address the cited questions. And the investigators have called for more comprehensive forensic analysis of socket quality and zinc creep.

"A potential mechanism for spelter socket zinc creep acceleration not considered in other analyses was the effect of low-current electroplasticity (LEP)," the report asserts. "The cables whose sockets failed were suspended in a unique and powerful radio telescope environment, capable of inducing current in the cables at some level. Electric current flowing through zinc has been found to increase its creep rate but under laboratory conditions [that were] significantly different than the spelter socket service in the Arecibo Telescope."

Existing data on zinc electroplasticity, according to the report, comes from experiments involving greater current over much less time. So further work needs to be done on low-current, long-term electroplasticity. The report also makes a number of recommendations about how such projects can be made safer with more funding and more diligent oversight and maintenance.

"The US National Science Foundation is grateful to the National Academy of Sciences for their thorough review of the circumstances resulting in the collapse of the 305-meter telescope at the Arecibo Observatory," an NSF spokesperson told The Register. "We welcome the opportunity to consider their findings and how we can incorporate their recommendations in the future." ®

Send us news