NASA studying a ‘ding’ on shuttle

James Oberg NBC News space analyst

Space shuttle experts are examining a small hole that was discovered on Atlantis after it landed — damage apparently done by a piece of space debris during the shuttle's flight.

The hole, labeled "Ding 18," is about a tenth of an inch (2.7 mm) in diameter and goes all the way through a quarter-inch (6 mm) aluminum honeycomb panel.

It was spotted on the surface of the aft-most segment of the starboard shuttle thermal radiator, one of two panels that unfold from the spacecraft's open payload bay doors in flight to dump excess heat from the cabin. The object missed the nearest pressurized coolant line by several inches.

The brief notice of the hole’s discovery appeared in the NASA minutes of a regular meeting at Kennedy Space Center in Florida, called the “Integrated Flow Status,” where the processing of all space shuttle components is discussed. The meeting is chaired by Robert Lightfoot, the manager of the Space Shuttle Propulsion Office at NASA's Marshall Space Flight Center in Huntsville, Ala., and is attended by both NASA and contractor specialists and managers.

The report came to light Wednesday on the independent NASASpaceFlight.com Web site, which posted an excerpt calling the hole the “first or second largest hit" in the history of the space shuttle program. Managing editor Chris Bergin, said the report was updated Wednesday and acquired from an unnamed source.

Another Web site, CollectSpace, posted a photograph showing the damage on Wednesday, and by Thursday NASA released the photos and schematics on its own Web site. MSNBC.com's efforts to obtain public comment from NASA on the debris strike have so far been unsuccessful, but sources discussed the damage and the follow-up inspections on condition of anonymity.

Because the impacting object apparently was vaporized, inspectors are now collecting samples from surrounding surfaces to try to figure out what the object was. In the past, residue has sometimes identified smaller impactors as being either human-made debris (such as paint chips from satellites) or natural micrometeoroids.

The debris damage comes only three weeks after the in space station crew noticed "a small hole" in one of the Russian segment's solar panels. A Sept. 14 internal status report said that the crew members downlinked photos of the damaged area, taken from a window in the station's Zvezda service module.

Russian Mission Control told NASA officials that four electricity-generating cells were affected, but power output remains at expected levels. Such impacts occur from time to time, but are usually much smaller. Photos of the solar-cell damage have not been publicly released.

Because Atlantis' "ding" is on a surface that was not exposed during the shuttle's fiery descent to Earth, the crew was not in danger. However, had the radiator been crippled, a mission emergency could have been declared and the shuttle would have had to land within a day, potentially aborting the station assembly mission.

Vigilant about damage
NASA managers have been much more vigilant about debris damage in the wake of the Columbia tragedy in 2003, which led to the loss of that space shuttle and all seven astronauts aboard.

NASA A cross-section diagram of the damage, released by NASA on Thursday, showed that behind the tenth-inch entry hole was a blown-out cavity 10 times as wide. The impact fell fortuitously right between two small pipes (shown in blue) carrying pressurized coolant through the radiator.

Shortly after Columbia's launch, a large piece of fuel tank insulation hit the leading edge of Columbia's left wing, smashing a head-sized hole in the wing's reinforced carbon-carbon panel, or RCC. That allowed superheated gases to enter the wing during the shuttle's atmospheric re-entry, destroying Columbia from within.

The daily reports from Mission Control to the crew didn't contain any reference to the damage, raising the possibility that it escaped detection during the numerous camera sweeps that were performed in flight. Those examinations focused on the shuttle’s thermal protection system — its heat-resistant tiles, blankets and reinforced wing panels — rather than on the radiator panels.

During the preparations for Atlantis' landing, NASA spotted what appeared to be several small objects floating near the shuttle — leading to an extra camera survey of the heat shield. The suspicion was that they were pieces of the shuttle knocked loose by debris impact, or jarred loose by thruster test firings.

That extra survey, like the mission's previous inspections, did not focus on the radiator panels.

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