The plate that doomed a dish

时间:2019-03-04 10:07:02166网络整理admin

AN overstressed steel plate gave way and caused the collapse of a 26-year-old radiotelescope in West Virginia last November, says a study commissioned by the National Science Foundation in the US. The loss of the dish has deprived American astronomers of their only instrument for detecting radio waves from space. The plate, which is 1 metre across, connected supports for the 90-metre dish to a bearing near the top of one of two support towers. Metallurgical analyses showed that the plate split along a line where tiny cracks had been developing for years between holes made for bolts. The failure came during routine motion of the telescope at the National Radio Astronomy Observatory in Green Bank, West Virginia. Ludwig Oster, the foundation’s programme manager for the National Radio Astronomy Observatory, said that high cyclical stresses and heavy loads caused progressive cracking from the bolt holes. The panel cleared maintenance engineers of negligence. The condition of the plate could not have been detected without dismantling the instrument, Oster said. Originally costing $850 000, the dish began operation in 1962, and was strengthened in 1966 after a design review. No one expected it to remain in use for more than a quarter century, as the US repeatedly upgraded it with new detectors rather than building new telescopes. Radio astronomers in the US and politicians in West Viriginia want a new telescope, but first they must find the $75 million needed to pay for it. The National Science Foundation’s budget for 1990 was complete before the collapse,