scope:

Description of Driving Event:

Three sections of a telescoping tube assembly at Pad B rotating service structure (RSS) fell while being extended to incorporate a planned modification (MOD). The MOD intended to eliminate binding that had been experienced during testing and verification. The falling tubes impacted and severely damaged the RSS and orbital maneuvering system pod covers. The contributing factor to this failure is that the fillet welds on tube "D" provided an outward ramp effect that caused excessive wear on the keepers and the eventual bowing of tube "C" which allowed less surface contact area between the welded stops and the keepers.