For all the crappy things that 2020 brought, the collapse of the Arecibo Observatory continues to sting. Since its demise, the failure has been under investigation, and a recent report sheds new light on what happened:
Long-term zinc creep-induced failure in the 57-year-old telescope’s cable spelter sockets was the root cause of the telescope’s collapse, the report says. Sockets filled with zinc held in place a set of cables suspending the telescope’s main platform over the reflector dish. Gradually the zinc lost its hold on the cables and allowed several of them to pull out, leading to the collapse of the platform into the reflector.
The failure sequence began with Hurricane Maria, over three years prior to the collapse, according to the report. Indications of cable pullout were minimal before the hurricane. Large and progressive cable pullouts could be seen during post-hurricane visual inspections, observation of which should have prompted remedial action. Safety factor calculations made following the first cable failure did not recognize the accelerated time-dependent materials failure process governing the eventual zinc pull out.
This is the first documented case of long-term zinc-induced creep failure despite a long history of usage over a century, the report notes. A possible explanation for the accelerated zinc-creep is long-term low-current electroplasticity, induced by the electromagnetic waves from the Arecibo Telescope. It recommends that the NSF should offer the remaining socket and cable sections for study by the research community.