Robert Daugherty, a senior engineer at NASA's Langley Research Center, said today his widely publicized emails outlining various dire scenarios for the shuttle Columbia's re-entry Feb. 1 were misinterpreted by the media. While he was "uneasy" after watching video replays of foam debris slamming into Columbia's left wing during launch, he had no inkling a catastrophe was about to unfold as he drove to work Feb. 1 to watch the shuttle's return to Earth.

"By all accounts, there was some ambiguity to this whole thing," Daugherty told reporters today during a teleconference. "We'd all seen the video, I'd seen the video, and even though we were absolutely doing 'what iffing' during the week, that was in my mind.

"So of course, there was some natural uneasiness on my part. But again, nothing that I believed (would lead to a catastrophe). I certainly believed everything was going to be perfectly fine and again, I expected to see pictures taken of the damaged area (of the wing) after they (the astronauts) were walking around the vehicle on the runway."

In the wake of Columbia's launching, concern about wing damage from foam debris that fell away from the shuttle's external tank 81 seconds after liftoff prompted an engineering analysis by Boeing engineers. NASA's mission management team ultimately accepted the company's conclusion, that while the wing might suffer significant damage due to battered tiles and aerodynamic heating, the shuttle could safely return to Earth.

But Daugherty was contacted to assess what the impact of possibly higher-than-normal heating to the underside of the orbiter might mean for Columbia's left-side main landing gear. And so began a series of emails that continued all the way through Jan. 31, the day before the shuttle's catastrophic re-entry.

The emails generated widespread publicity because they seemed to indicate growing concern among mid-level engineers that Columbia might somehow be at risk. The discussion was not passed on to senior NASA managers - or to Columbia's astronauts - prompting some observers to question NASA's management system.

In an earlier teleconference, two Johnson Space Center participants in the email exchanges said no one believed Columbia faced a serious problem and that all of the post-analysis discussion was simply a matter of "what iffing," part of a normal engineering dialogue aimed at making sure flight controllers in Houston were prepared for any landing gear issue that might crop up.

"Honestly I was very surprised by the attention my writing received," Daugherty said today. "I view my involvement as a small sideline focused on landing issues. I've been in somewhat of a quandary. I really do believe the best thing I can do for the investigation is to talk to the (Columbia Accident Investigation Board) first. On the other hand, it's frustrating that my work is being misinterpreted. My quandary has now been relieved since the board has said they don't mind if I speak up. So I want to clear the air as much as possible."

Daugherty's boss, Mark Shuart, director of the materials and structures branch at Langley, said NASA Administrator Sean O'Keefe visited the Virginia facility in the wake of Columbia's destruction and "I'm the guy who told him this was not an engineer waving a red flag and nobody paying attention. ... That was far from the facts."

In one of the emails, Shuart wrote: "I am advised that the fact that this incident occurred is not being widely discussed."

Worried more about the impact of re-entry heating on Columbia's left main landing gear tires than he was about a high-altitude catastrophe, Daugherty emailed Shuart later that "we can't imagine why getting information is being treated like the Plague. Apparently, the thermal folks have used words like they think things are 'survivable,' but 'marginal.' I imagine this will be the last we hear of this."

Daugherty said today this email was widely misunderstood. It was written in response to problems getting simulator time scheduled to determine the consequences of landing with flat tires.

"The comment about getting information like the plague, first of all it was work between friends and I tend to be a little more colorful when I'm with my friends," he told reporters. "Again, it was frustration in a sense because there were simulations already going on and approved that were in a sense very similar to what we were after, but different enough that we couldn't just jump in in the middle of the astronaut training that was going on. And again, I always want to get the information I'm after immediately so there was some frustration there about getting that information. And that comment was truly very specific, just to the issue of trying to get these simulation runs."

Asked if the emails in general should have been passed on to more senior managers, Daugherty said "I don't think it should have. My email was technical issues that I intended to have technical people discuss and that's exactly what happened."

"There really wasn't a level of concern," he said. "I know you can get that from the emails. But these were emails between two long time colleagues and we spent a lot of time talking in the emails like we might talk in person. There was not concern from my standpoint in the emails. I had no clue whatsoever that the (Boeing) analysis might or might not be right, we were simply looking into well, let's be conservative, what if the analysis weren't right, let's think of the things you might want to plan for and have a game plan in your back pocket."

Asked if the astronauts should have been informed, Daugherty said "absolutely not, because they weren't really concerns, they certainly weren't warnings. They were simply, be ready for anything, just like there are a myriad of other things (flight controllers) have plan Bs in their console books. And this is nothing more than some more extensive plan Bs in this slightly unusual situation. They absolutely met my expectations and absolutely handled it at the level I intended."

But it was, in fact, an unusual situation. Shuart said he could not recall a similar discussion between Langley and Johnson Space Center engineers about potentially serious problems during a shuttle mission.