Shuttle Disaster May Be Linked to Peeling Paint at Launching Complex

Peeling paint at NASA’s aging launching complex in Florida may have played a role in the Columbia disaster, investigators said Tuesday.

The leading edge panels that protected Columbia’s wings from 3,000-degree temperatures during reentry had dozens of pinholes, apparently caused by contaminants from paint flaking off the launching towers at Kennedy Space Center, investigators said.

Each of the shuttle’s 44 leading edge panels had developed from 20 to 40 pinholes during previous missions, caused by zinc oxide from the decaying paint that was washed off the towers by rain, according to the Columbia Accident Investigation Board.

The peeling paint, if it did play a role in the loss of the shuttle Feb. 1, would represent an astounding consequence of NASA’s sometimes dilapidated infrastructure. The launching towers are massive steel structures that provide access to the orbiter and help connect it to fuel and electrical lines before rocket ignition.

NASA knew about the pinholes in the leading edges, which are made of a high-temperature material known as reinforced carbon carbon; the agency had set a standard that any hole larger than 0.04 inches would be repaired.

But investigators are wondering whether the existence of so many pinholes and repairs may have left the leading edges vulnerable.

It is believed the leading edge of Columbia’s left wing was struck by foam falling off the shuttle’s external fuel tank 81 seconds after launching. The foam could have punched a hole in an edge weakened over 20 years by space flights and repairs to pinholes.

The board is not certain zinc oxide caused the pinholes, but it is the prime suspect. Zinc oxide is used in the primer, underneath the paint on the launching towers, according to board member Maj. Gen. John Barry.

“The pad top coat hasn’t been refurbished and the primer becomes exposed,” Barry noted.

Other possible explanations of what ate away the leading edge include salt spray from the Atlantic Ocean and chemical treatments used in refurbishing the leading edges between missions.

The board, which held a news conference Tuesday, is not near determining a cause of the Columbia accident. Even if the cause involves foam debris damaging the leading edge, the board’s findings must be far more precise and detailed, said Chairman Harold W. Gehman Jr.

A number of other parts on the leading edge could have failed and opened a breach into the left wing.

The second likely suspect is a part called a carrier panel, which forms the seal between the curved leading edge panel and the wing surface.

Since the accident probe began, the board has been trying to identify an object that was observed on radar flying near the shuttle during its second day in space. Officials are confident that the object came off the orbiter, and their analysis so far has eliminated every possible material except for the carrier panel, Barry said.

Gehman noted that astronauts previously have seen pieces of the shuttle, like washers and thermal blankets, floating by them in space. And a missing carrier panel would cause a breach in the wing, although investigators still are far from understanding whether that would explain the accident.

Roger Tetrault, a board member, said he believes the breach has been narrowed down to either the leading edge panels or the carrier panel; still, the board has not formally ruled out the possibility that heat-resistant tiles or other parts may have been at fault.

The board also disclosed Tuesday a number of new factual findings. The flight data recorder that was recovered by search teams in Texas indicates that abnormal heating began almost as soon as the orbiter hit the atmosphere, about four minutes after the “entry interface.” That makes it clear that the shuttle entered the atmosphere with a serious breach, rather than a minor hole that became enlarged.

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Vartabedian reported from Los Angeles and Hart from Houston.