Although mission managers agreed that any damage was not life threatening, engineers responsible for the shuttle's tires, brakes and landing gear at NASA's Johnson Space Center (JSC) here and Langley Research Center in Hampton, Va., decided to review their options based on the approach of "what if this analysis is wrong."

"They were doing this on a purely, what if, devil's advocate type scenario, which they discount in their e-mail as being implausible and something they did not expect to see happen," said NASA spokesman James Hartsfield.

During the next few days the e-mails flew back and forth among the engineers, some writing more colorfully than others, in describing what they thought might happen if the tile damage analysis was wrong and how they might have to end the shuttle mission.

In one case, Kevin McCluney, a mechanical engineer at JSC, displays a keen understanding of his systems in describing what might happen if hot gas from re-entry were to somehow get inside the left-hand wheel well and begin causing sensors to fail -- laying out a scenario that is nearly identical to what actually happened.

"What does the alert (flight controller) do in the event such a signature as described above? There are only a limited number of choices," McCluney wrote. Those choices ranged from doing nothing, to attempting a landing or bailing out.

"Beats me what the breakpoint would be between the two decisions," McCluney said.

In another e-mail, flight controller Jeffrey Kling wrote what is the most haunting phrase found within the package of communications when he described what he thought would be his team's recommendation if they started to see some of the sensor indications described.

The choice ``is going to be to set up for a bailout (assuming the wing doesn't burn off before we can get the crew out),'' Kling wrote adding parentheses to his off-the-cuff, but prophetic, comment.

Despite such dramatic talk, none of the people writing in their e-mails openly or directly disagreed with the tile debris analysis.

"Serious scenarios are discussed a lot in Mission Control, in a what if-ing sense, that can occur. If the flight controllers involved had concerns, they would have elevated them. They did not have concerns that needed to be elevated, that was their conclusions," Hartsfield said.

The e-mails also provide some insight into NASA's decision not to seek the help from Department of Defense in taking pictures of Columbia's belly while it was still in orbit.

There have been rumors that the DOD was asked to take satellite pictures of Columbia, and as it turned out that request was made, but it came informally between shuttle and military managers at Kennedy Space Center and Patrick Air Force Base in Florida.

Before any pictures were taken by the military, the formal process set up for such requests put a stop to it because NASA officials by then had concluded the images wouldn't show anything, and the tile damage assessment was such that there were no concerns.

The e-mails were, in effect, an apology from NASA to the Air Force and an assurance that in the future such requests would only be made, and should only be accepted, through the formal process set up between the two governmental agencies.