Fleet impact resulting from a space shuttle Columbia main engine controller wire failure during Mission STS-93

A main engine controller wire short-circuited 5 s into the launch of the shuttle Columbia during mission STS-93, causing a loss of redundancy to two of the three main shuttle engines. The short circuit occurred when vibrations caused an energized wire bundle, which had unknowingly been mechanically damaged previously, to make contact with an adjacent screw that had an area of raised base metal exposed. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron spectroscopy for chemical analysis, along with mechanical tests designed to simulate the conductor damage, were used to determine the root cause of the failure. The findings from the investigation led to a fleet-wide inspection of orbiter wiring.