Endeavour preps for spacewalk, closer look at tile damage

Endeavour astronauts are preparing for the first of four planned spacewalks early Friday while NASA continues to review a damaged heat shield tile that may require closer inspection.

The tile was apparently gouged by ice falling from the shuttle's external tank during Monday's morning's launch from Kennedy Space Center.

NASA will decide by Friday whether to perform a so-called "focused" inspection on Saturday, using a boom with cameras and lasers to scan the area of interest in greater detail.

Though such inspections are not common, LeRoy Cain, the head of NASA's mission management team, said he was not alarmed by the damage.

He said a closer inspection would provide higher fidelity images that might allow analysts to back off from overly conservative assumptions and likely clear any need for repairs.

“I am not concerned about the damage that we’re seeing here, and it’s certainly not alarming,” said Cain, citing confidence in the procedures for assessing tile damage.

The tile in question is located behind the right landing gear door. It measures about 3.2 inches by 2.5 inches and 0.7 inches thick. One other tile, on the right inboard elevon, has not yet been cleared but is expected to be.

Cain said a similarly damaged tile on a 2007 Endeavour flight was cleared after a focused inspection. The commander of that flight was Scott Kelly, brother of current commander Mark Kelly.

The 10-year-old tank that helped launch Endeavour this week did not have all of the modifications made to new tanks after the 2003 Columbia disaster, and Cain said some debris was expected. The ice apparently originated from a liquid oxygen propellant feedline bracket.

If the damage turns out to be more serious than thought, spacewalkers could attempt repairs.

Meanwhile, the mission marches on. Astronauts Drew Feustel and Greg Chamitoff plan to kick off the spacewalking activity around 3:15 a.m. EDT.

Over six-and-a-half hours, they'll retrieve and install science experiments, install a communications antenna and route jumper cables in preparation for topping off a leaking coolant line on the mission's second spacewalk, planned Sunday.

You can watch it all live here by clicking the NASA TV box at right to launch a viewer.