Cracked plate caused telescope collapse.

Cracked plate caused telescope collapse

The sudden collapse last November of the 300-foot-diameter radiotelescope at Green Bank, W. Va., probably resulted from the fracture of a single, highly stressed steel plate, according to an investigation by an independent panel of engineers reporting to the National Science Foundation (NSF). The panel found that parts of the telescope, which was constructed in 1962 of a fine aluminum mesh held by steel supports, experienced far greater stress than would be allowed in a structure built today.

"From the beginning of its life, the structure was marginal with respect to structural failures of a minor or perhaps major nature," the panel reports. Designed to last only 10 years, the radiotelescope simply wore out.

The plate in question was a critical component in the instrument's support structure and endured great stresses whenever the telescope was moving. The plate itself was hidden from view and could not be examined routinely without dismantling the telescope. A metallurgical analysis of the remains of the plate revealed small cracks, which apparently grew until the plate suddenly failed.

Attention is now likely to focus on plans to replace the instrument. NSF's top choice for its next astronomy facility is an observatory geared to searching for gravitational waves. Known as the Laser Interferometer Gravitational Wave Observatory, the observatory would consist of two facilities located near the east and west coasts and cost about $100 million. However, West Virginia politicians insist that NSF should give higher priority to replacing the collapsed radiotelescope with a modern instrument, at a cost of $75 million (SN: 11/26/88, p.342).