NASA Weighs Heat Shield Dings on Shuttle
The space shuttle Endeavour's 15-story external tank floats away after helping launch the STS-127 mission on July 15, 2009. This view is a NASA TV still from HD video taken by astronauts to be used to find where bits of foam insulation fell off the tank during liftoff.
Credit: NASA TV.

NASA is not too worried about debris that appeared to fall from the space shuttle Endeavour's external fuel tank during its liftoff Wednesday, but is perplexed about why the bits of foam insulation fell from an unexpected spot.

During Endeavour's launch, about nine to 12 bits of debris appeared to fall, though most of these occurred after the period where falling pieces are likely to cause damage.

Two debris events appear to have struck the shuttle when they could cause damage, and what appeared to be slight coating damage on some tiles was seen in launch video footage, mission managers said. Endeavour?s heat shield will get a full standard inspection to determine its health during the mission, they added.

Insulating foam from the tank can impact the orbiter and damage the sensitive heat shield tiles and panels lining its belly, nose and wings.

Mission managers were surprised by the pattern of foam loss seen on Endeavour's external tank, as it fell in long slivers from the middle area of the tank, which hasn't been a problem before.

They plan to study the problem by analyzing other external tanks on the ground being prepped for future missions to see if the foam in this area is loose on other tanks. The work could potentially impact the planned launch dates of future flights, but it's too soon to tell, said mission management team chair John Shannon during a Thursday briefing.

"Strips of the foam covering the inner tank structure just kind of peeled off the primer layer of metal," Shannon said. "We don?t understand why that actually happened. It looks like the base primer was not holding on to the foam well."

Though the pattern is unusual, it doesn't appear to pose a serious threat to the shuttle this time.

"The foam loss was so late there was not a lot of aerodynamic forces going on at that point," Shannon said. "We're not worried about this flight but we need to understand what was going on for the next flight."

To be sure that Endeavour is safe and its heat shield unscathed, NASA has a number of normal precautions in place.

Astronauts aboard the shuttle spent about seven hours today poring over the heat-resistant reinforced carbon-carbon panels lining Endeavour?s leading wing edges and nose cap, using a sensor-tipped inspection pole. That data is yet to be analyzed in detail, but no warning signs were reported so far.

The shuttle is scheduled to dock at the International Space Station tomorrow at 1:55 p.m. EDT (1755 GMT). As the vehicle approaches, it will make a fly-around to expose Endeavour's underside while astronauts aboard the station snap detailed photographs. Those will be sent down to engineers on the ground to search for possible damage.

Endeavour is beginning a 16-day mission to deliver a Japanese-built outdoor science platform and a new long-duration crewmember to the station. The mission was delayed for more than a month on the ground by bad weather and a gas leak, but is now proceeding smoothly, lead flight director Paul Dye said.

"Our team is sharp and ready to execute the mission," he said Thursday. "The best thing about today was that there wasn't much off-nominal. The crew's been ahead or on schedule all day."

SPACE.com is providing continuous coverage of STS-127 with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.