Tiles May Be Key to Columbia’s Tragic End

JOHNSON SPACE CENTER (Reuters/The Times)–The end of Columbia was swift and brutal. Forty miles above the Earth and just 16 minutes from touchdown at Cape Canaveral–it was ripped apart.

What triggered the disintegration of America’s oldest shuttle orbiter on its 28th flight is to be the subject of intense inquiry inside NASA

Yesterday attention was focused on an incident–little-noticed at the time–just over a minute after launch on January 16. A piece of silicone foam rubber insulation fell off the main fuel tanks at its forward attachment point and was dashed into a puff of dust by impact with the left wing.

It was the second time in the past three launches that insulation foam had broken free. On the last Atlantis flight in October 2002–a similar piece fell off–hit the skirt of the booster rocket and did damage described as superficial–but still enough to be noticeable when Atlantis landed. As a result–Columbia’s crew had been asked to take still and video pictures of the external tank after launch–to try to work out why the foam kept breaking free. The films–and any evidence they may have contained–have been lost in Columbia’s descent.

NASA issued a statement on Sunday saying that human remains were found–and that it could not confirm that remains of all seven astronauts had been recovered.

At the entrance of the Johnson Space Center in Houston–dozens of signs–flowers and balloons were placed in tribute to the fallen astronauts. The crew was mourned across the United States at church services and visits to space centers to pay respects.

The United States was not alone in its sorrow. The crew of Columbia–five men and two women–included Kalpana Chawla–an Indian-born woman–and Israeli air force Col. Ilan Ramon–the first Israeli astronaut.

Data beamed down from Columbia–which first flew 22 years ago–showed the temperature on part of the left fuselage spiked 60 degrees Fahrenheit (32 C) in five minutes as the spacecraft was re-entering the atmosphere.

NASA was examining whether there could have been damage to the shuttle’s thermal tiles. Columbia’s left wing was banged 80 seconds after launch by insulation from its fuel tanks–but NASA engineers believed it caused no serious damage to the heat shield.

The tiles–ceramic and several inches thick–are attached with a powerful cement. But shuttles have lost tiles before in space flight and come down intact. This time–it seems possible that the area of damage was the critical one along the wing’s leading edge.

There are other possibilities. The simplest is that in the roll maneuver–Columbia’s structure was overloaded and something broke. Again–the wing is the most likely area–but this should not have happened unless the stresses were greater than planned–or the strength of the wing had been sapped by corrosion or fatigue. Columbia was the oldest of the orbiters–although Discovery has carried out 30 missions to its 28.

Officials have ruled out a simple loss of control. They have also ruled out sabotage–pointing out that Columbia was out of range of a ground-to-air missile. Structural failure seems the obvious explanation. What caused it will be the key question.

NASA has grounded the three remaining shuttles until the disaster’s cause is found and corrected.

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