NASA studying a ‘ding’ on shuttle

Missed opportunity in 2003?
The extra checks were made in an atmosphere haunted by a tragic missed opportunity leading up to the Columbia catastrophe. Investigators say a piece of Columbia's broken heat shield panel shook loose during some thruster firings on the day after launch and drifted off into space. For many minutes, the debris was well within range of the shuttle’s cameras and the crew members’ eyeballs — but nobody noticed.

This was realized weeks after tragedy struck, when U.S. Air Force space radar trackers reviewed the raw data collected — but not evaluated — during the mission. The piece was tracked by sensors around the world, at such precision that its shape and mass could be estimated. It matched a broken-off, curved panel with supporting ribs.

Had the object been seen, many flight controllers now feel, enough suspicion would have been raised to look more closely for heat shield damage. The hole in the wing might have been found, and NASA might have been alerted to the threat.

Perhaps some emergency repair or rescue could have been pulled off, or perhaps not — post-disaster analysis reached no firm conclusions on that score. But in any case, the shuttle crew and their support staff at Mission Control would have gone down swinging, rather than being blindsided by disaster.

What ifs for the new damage
Shuttle specialists familiar with the latest "ding" on Atlantis told MSNBC.com that it was difficult to say for sure how bad the damage might have been if the impacting object had hit elsewhere on the shuttle. These specialists spoke on condition of anonymity because they were not authorized to discuss the situation publicly.

"First assessments were if it had hit RCC it would have penetrated but would be within the allowable damage criteria," one said in an e-mail. Another source suggested, however, that an oblique or glancing impact could have wreaked significant damage and required a repair attempt.

Over the course of the shuttle program, NASA has developed hardware and software measures to guard against a scenario in which an impact penetrates a coolant line on the radiator and leads to the loss of that critical system. Extra shielding has been welded over the lines, and the shuttle's computers monitor the lines for any pressure drop, ready to shut off isolation valves to prevent the loss of coolant fluid.

The shuttle can also be cooled by expelling water through a system called the flash evaporator — which is meant to operate at the beginning and end of each flight, when the payload bay doors are closed. The apparatus could be turned on to supplement a degraded radiator panel system, but that would force the shuttle to return to Earth at the earliest opportunity.

The specialists agreed that the least vulnerable structures on the shuttle would include its triple-paned windows. Any small debris hitting the outer panel would vaporize, and if debris penetrated to the second layer, it would be in the form of a fast-moving dust cloud with much less punch than the original solid object.

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