After years of growing concern about its poor condition, the Arecibo telescope's famed reflector was suddenly ruined by the collapse of its receiver into the dish in 2020. Engineers have completed their report into the disaster and its causes: Failure Analysis of the Arecibo 305 Meter Telescope Collapse [National Academies]
After analyzing the data and the extensive and detailed forensic investigations commissioned by the University of Central Florida and the National Science Foundation (NSF),' the committee consensus is that the root cause of the Arecibo Telescope's collapse was unprecedented and accelerated long-term zinc creep induced failure of the telescope's cable spelter sockets. The finding of creep aligns with the other forensic investigations. "Each failure involved both the rupture of some of the cable's wires and a deformation of the socket's zinc, and is therefore the failure of a cable-socket assembly." While the cable system was upgraded in 1997 with cable safety factors greater than two, the telescope collapsed after the failure of several cable-socket assemblies that were not loaded at the time of the first socket failure above half their nominal design strength.` Failure despite a factor of safety of 2 was possible because the accelerated time-dependent materials failure process governing eventual zinc pull out (i.e., power law creep [PLC]) occurred at stresses below 50 percent of the cable strength.
The zinc cable terminators deteriorated quicker than expected. That said,
Upon reflection, the unusually large and progressive cable pullouts of key structural cables that could be seen during visual inspection several months and years before the M4N failure should have raised the highest alarm level, requiring urgent action. The lack of documented concern from the contracted engineers about the inconsequentiality of the cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming.
