Jeff Kling, the mechanical systems officer - MMACS - in mission control during the Columbia tragedy. Photo: NASA TV/Spaceflight Now

Mechanical systems officer Jeff Kling, the flight controller who first noticed problems in the shuttle Columbia's left wing during re-entry Feb. 1, said today he had no idea a disaster was about to unfold and that "what-if" discussions he had by email the day before were just that and not an indication of any real concern on his part.

In a teleconference this evening with a small group of reporters, Kling said he fully expected a normal re-entry and landing when he showed up for work that morning, despite knowing a piece of debris from the shuttle's external tank had hit the ship's left wing during launch.

Kling said the flight control team was satisfied with the conclusion of a Boeing analysis of the impact, which concluded Columbia could land safely.

"From our console standpoint, there was not a huge concern out there," he said. "We had proper teams looking at thermal analyses and what we thought was a good result. I had no reason to doubt the thermal analysis that said there was not going to be any burn through on the vehicle.

"The emails we had were what-if kind of scenarios where we talked about, like we do in our normal jobs, we bat things around and say, you know, what if, and work through the whole thing. Because I had confidence in the thermal analysis I was not at all concerned with the health of the vehicle on entry day.

"However, when events started unfolding, there was a little bit of disbelief right at first when we got the first indications and we just kind of went down that path of, you know, I can't believe this is happening and what did I miss, what did we miss as a team? But we certainly never anticipated this and it was not a concern at all from our console prior to the deorbit burn."

Following the Boeing analysis and its formal disposition on Jan. 28, an engineer at NASA's Langley Research Center in Virginia raised questions within the landing gear and flight control communities about what excessive heating on the left wing might do to the left main landing gear. Emails between the various participants in the discussion were released by NASA today and last week.

The emails show a spirited discussion about what to do if Columbia's landing gear really was damaged. But Robert Doremus, head of the mechanical systems group at the Johnson Space Center, said the discussion was little more than a routine exercise that serves to keep the team sharp.

"We discuss cases sometimes that we don't necessarily expect to happen," he said. "But in doing so, we expand our own knowledge and kind of challenge ourselves to think outside the box and be ready for things."

The discussions were not passed onto senior managers because "again, it was more of an exercise within our group."

"There weren't any new data that came to us originally that said the tile problem might be worse than the analysis said," he explained. "Had there been data in that email that we got, yeah, there would have been quite a bit of concern raised and we would have definitely started looking at what do we need to change as far as entry is concerned.

"But what we got was well, if the analysis is not correct, this is what it might look like and we were joining in on that discussion. But it was not an alarm because it did not contain additional information that would have told us we have a concern."

Kling said the reality of what was happening to Columbia on Feb. 1 did not fully sink in until he saw video showing flaming wreckage streaking across the Texas sky.

"On entry day when we lost the first set of sensors, there was a little bit of disbelief and some concern but we've been trained to do that sort of stuff before," he said. "The fact it was on the left side, it kind of raised your eyebrows a little bit with the first set of sensors.

"When the second set came along, you start playing back some of the things that you went through, and wondering. It didn't actually sink in for me probably until I actually saw some of the taped video footage of the vehicle itself. The rest of the time, I was going through my job, talking to the escape officer, looking for evidence of the crew bailing out or whatever."

But even if the flight control team had understood the severity of the problem well before Columbia's re-entry, Doremus said there was nothing NASA could have done to save the shuttle or even to maneuver it to a point where the crew could bail out.

"We already minimize as best we can the entry profile to make the orbiter have the safest possible entry that it can have," he said. "I don't think, aside from a few tweaks, we could have gotten there with our particular scenario."

See today's earlier story for a detailed look at the emails and "what-if" scenarios in question.