One day before the Columbia disaster, senior NASA engineers raised concerns the shuttle's left wing might burn off and cause the deaths of the crew, describing a scenario much like the one investigators believe happened. They never sent their warnings to NASA's brass.
"They were talking about various scenarios, various 'what if' scenarios even the day before re-entry," said CBS News Space Consultant Bill Harwood.
"Why are we talking about this on the day before landing and not the day after launch?" wrote William C. Anderson, an employee for the United Space Alliance LLC, a NASA contractor, less than 24 hours before the shuttle broke apart.
After intense debate - occurring by phone and e-mail - the engineers, supervisors and the head of the space agency's Langley research facility in Hampton, Va., decided against taking the matter to top NASA managers.
"I think this is part of the process that NASA normally goes through when they do simulations between missions; they always are pretending things have gone wrong," reports Harwood. "They say that this was simply a part of that and certainly nothing all that out of the ordinary.
"But you do have to wonder if management shouldn't have been involved in some of these discussions as this went on."
Jeffrey V. Kling, a flight controller at Johnson Space Center's mission control, foresaw with haunting accuracy what might happen to Columbia during its fiery descent if superheated air penetrated the wheel compartment.
Kling wrote just 23 hours before the disaster that his engineering team's recommendation in such an event "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 the following day was among the first in mission control to report a sudden, unexplained loss of data from the shuttle's sensors in the left wing.
The e-mail released Wednesday describes a far broader discussion about the risks to Columbia than the concerns first raised three days earlier by Robert Daugherty, a NASA senior research engineer at Langley. He was mostly concerned about the safety of the shuttle landing with flat tires or wheels damaged from extreme heat.
Among the messages was one from Daugherty's boss at Langley, Mark J. Shuart, to another Langley supervisor, Doug Dwoyer, describing Daugherty as "the kind of conservative, thorough engineer that NASA needs."
"I can only hope the folks at (Johnson Space Center) are listening," Shuart wrote.
One e-mail, from R.K. "Kevin" McCluney, a shuttle mechanical engineer at Johnson Space Center, described the risks that could lead to "LOCV" — NASA shorthand for the loss of the crew and vehicle. But McCluney ultimately recommended to do nothing unless there was a "wholesale loss of data" from sensors in the left wing, in which case controllers would need to decide between a risky landing and bailout attempt.
"Beats me what the breakpoint would be between the two decisions," McCluney wrote.
Investigators have reported such a wholesale loss of sensor readings in Columbia's left wing, but it occurred too late to do anything — after the shuttle was already racing through Earth's upper atmosphere and moments before its breakup.
Meanwhile, NASA Administrator Sean O'Keefe was set to appear at an appropriations hearing in Washington on Thursday. He wrote to the House Science Committee in prepared testimony that the independent board investigating the disaster "has made significant progress in organizing its work to determine the cause of the accident."
O'Keefe wrote that all exploration is inherently dangerous. He cited the death of a young Army lieutenant aboard the Wright flyer in 1908, saying, "So, too, from Columbia we will learn and make human space flight safer."
In other developments, accident investigators said they wanted to know more about a mysterious object that almost certainly fell off the shuttle and was flying alongside the spacecraft during its second day in orbit.
The object orbiting near Columbia was never noticed during the flight. After the shuttle's destruction over Texas, just 16 minutes short of its planned Florida landing, the Air Force Space Command began analyzing radar data and noticed the object.
Initially, NASA said it suspected the object might be frozen waste water dumped overboard or an orbiting piece of space junk that the shuttle happened to encounter.
But Air Force Brig. Gen. Duane Deal, a board member, discounted both possibilities Tuesday and said the object almost had to have come from the shuttle itself.
"You or I could invent a dozen scenarios," Deal said. "It could have been something loose that separated, it could have been something inside the payload bay." It also could have been part of the left wing, where all the overheating and other troubles developed during re-entry.
He described the object as about 1 foot by 1.3 feet in size and said it was flying in tandem with Columbia one day into the mission. It was within 50 feet of the shuttle and, within that first day, started separating farther and farther away until it burned up on re-entry three days later, he said.
"It was something that more than likely came loose," Deal said.
The composition of the object is unknown, but it was lightweight and not dense, Deal said. Lab testing is planned by the Air Force and NASA to determine the material, based on its reflectivity.
CBS News Space Consultant William Harwood has covered America's space program full time for more than 15 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.