Over two months have passed since the disaster and the best answer is probably the first
The fragments that hit the wing during takeoff. This is now the preferred theory, despite all the competing theories
Two months after the space shuttle Columbia crashed in the skies over Texas, accident investigators have examined every possible theory, no matter how wild - a deadly micro-meteorite, high-altitude lightning, and perhaps even scientific experiments on board.
However, the strongest theory seems to be the one that appeared on the first day - the theory of the insulating foam that was torn from the external fuel tank after takeoff and collided somewhere on the left wing of the shuttle, causing enough damage to lead to the disaster.
"This is the leading theory, but we still don't have the final answer to that," says Scott Hubbard, a member of the Columbia Disaster Investigation Committee and senior NASA official.
Weeks of investigation since the February 1 disaster have mostly uncovered evidence that backs up the original theory. NASA knew early in the 16-day mission that pieces of the foam fell from the fuel tank and hit the left wing, but the senior mission officials decided that there was no danger.
Just last week, tape from an old-fashioned recording device was unearthed from the Texas mud, revealing that the warming problems that developed during Columbia's re-entry into the atmosphere ended earlier than expected.
The recording film revealed an unusual heating trend in the left wing about a minute after the shuttle entered Earth's atmosphere over the Pacific Ocean.
The researchers see this as evidence of the fact that the shuttle was "severely injured" earlier, and that plumes of hot air entered through a hole that was already in the wing and began to row in.
They were unable to come up with a plausible theory that the crack in the wing was caused by space junk or something else that hit them in orbit, and they left the theory of the impact from the foam fragments as the most likely cause of the impact.
The researchers are also taking a closer look at the video, hoping to notice changes in the flashes seen on the indicators and screens.
In the coming weeks, experts will carry out several experiments to diagnose how much damage the foam could have caused. In fact, NASA officials were so concerned about the foam that days after the disaster they contacted a research institute and asked to perform impact tests on the foam.
Findings from these tests, along with other evidence, may provide circumstantial evidence to find the root cause of the accident.
Now that researchers know that Columbia experienced problems so early in its reentry, they will take a closer look at the cockpit video -- the one that showed the smiling crew members going about their work.
When the film was first seen no one believed it would provide any value to the investigation because it ends four minutes before what was believed at the time to be the first signs of the disaster. However, now that the researchers know that the first temperature peaks occurred earlier, they are considering whether they can get something from the crowds that were in the cockpit and the screens or from looking out the window of the furnace and the atmospheric flashes outside.
A senior NASA official said that no one is claiming that the astronauts knew something was wrong at an early stage, but he commented: "Nothing should be ruled out. We look at everything."
At this point, the head of the investigation team said that it is too early to unite around the foam theory. Harold Gehman repeatedly said that he and his colleagues were suspicious and unwilling to fall in love with Torah theory."
The shuttle fleet has been in use for years, Columbia, which first took off in 1981, was on its 28th flight.
"Just because a mysterious object that flew away from Colombia on its second day in orbit was certainly close to a panel from the end of the wing, it does not mean that the crack happened exactly where the panel was" say the team.
"You can't just take such a leap of faith," says committee member Roger Teterlot, a former executive at a company that built nuclear submarines.
Gehman has a gut feeling that the foam wasn't the only problem NASA would have to fix before it could launch another shuttle. The age of the spacecraft and ground equipment may also be considered contributing factors.
Columbia first flew in 1981 and this was the 28th flight.
"In my opinion, foam that hits a healthy spacecraft would not have caused it any damage," Gehman said. "However, foam that affects the shuttle has some wear and scratches, and especially in Colombia, which has a history of "hot" landings and stiffer wings, and congestion during take-offs. Well, if we put all these together - which I do - and you get a shuttle that, according to my measurements, is much older than its nominal age."
Last week, researchers cited a new theory that may have somewhat undermined the strength of the shuttle's wing. Pin holes were drilled in the carbon heat sink panels located at the leading edge of the wing. Rust marks were caused by an army of elements that leaked from NASA's ancient launch towers, and could have weakened the panel until breaking off a 60-centimeter-long, XNUMX-pound piece of foam could damage it, some experts said. Thus the investigative team appears to be looking at all the wear and tear that has accumulated over the years in the aging ferry fleet.
And in a week or so, a series of attempted attacks will begin at the Southwestern Institute in San Antonio. The foam will shoot at real parts of space shuttle wings - some of them the age of Columbia at a speed of about 700 km/h, the speed of the shuttle at that stage of the takeoff, 81 seconds after launch.
"We are trying to narrow down the search to the front end of the wing, but the crack could have opened in at least five places, Tetralot said. "We have to comb our way through all of these. If we fail to do this step in the right way and give the wrong recommendation, another accident may occur."
