Jul 2 1986
From The Space Library
The Delta 178 rocket accident that occurred on May 3, 1986, was caused by mechanical damage to wiring caused by vibration during flight. The rocket's first failure-after 43 flights since 1977-was attributed to a design change, a shift from polyvinylchloride (PVC) insulated wiring to Teflon insulated. Unlike PVC, which is over-wrapped for greater abrasion protection, Teflon wiring bundles are over-wrapped in only a very limited number of locations; the abrasion resistance of mechanical damping was not adequately considered when making the change. The investigating board recommended a review of the booster electrical control system and possible design changes, verification of the quality of all connectors, and a reemphasis on highly attentive, quality workmanship.
Another study released concerned the Titan 34-D mishap of April 18; it determined the cause of the accident to be insulation inside one of the two solid rockets being pulled away and allowing "burn through". Neither accident was deemed the result of any major design flaw and, subsequent to minor modifications, the United States planned to resume untended rocket launches.
The investigating board also observed potential problems resulting from high-humidity conditions for vehicles stored at the Kennedy Space Center, to instrument limitations, and lack of protection from contamination of the Rocketdyne engine relay box. These problems were not directly connected with the Delta 178 rocket accident or the Titan 34-D mishap. (NASA Release 86-85; W Post, Jul 3/86; WSJ, Jul 3/86; NY Times, Jul 3/86; B Sun; Jul 3/86)
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