NASA Johnson Space Center documents from as far back as 1988 show that wing roughness, similar to that associated with the orbiter Columbia's left wing, could result in a catastrophic burn-through when combined with potentially significant wing impact damage resembling that being investigated in the Feb. 1 reentry accident.

One of these documents (right) presented in a 1988 shuttle flight readiness review specifically spelled out how gouge damage at or behind the wing glove could result in temperatures exceeding 3,000F, essentially the tile melting point-if the damage were positioned near wing roughness like that associated with Columbia.

The former chief of the NASA Astronaut Office, Robert L. (Hoot) Gibson, who flew five shuttle missions, four as commander, told Aviation Week & Space Technology that "when Columbia went down, the first thing I thought was, 'oh man, I wonder if it started on the left wing.'"

Telemetry would later show that, indeed, it did start with the left wing, about which Gibson, a retired Navy captain, had raised significant concerns following Columbia's STS-28 flight in 1989. He raised those concerns relative to the higher level of roughness on the Columbia's left wing as part of assessments on why the vehicle's wings transitioned from laminar to turbulent flow at least 3 min. earlier on that flight than on previous reentries.

Subsequent analysis would show that Columbia's wings on its first flight in 1981 also transitioned to more thermally stressful turbulent flow as early as about Mach 14 versus Mach 8-9 as expected, Langley Research Center engineers said.

The earlier transitions meant that Columbia on those flights spent considerably longer in the hot phases of the reentry-a significant issue for tile damage-especially if damage had occurred during launch.