NASA opts to forego focused inspection

NASA mission managers today opted to forego a focused inspection of Discovery's heat-shield, a move that clears the way for the shuttle's crew to concentrate on challenging International Space Station construction work.

The decision also shows the managers have no concerns about a slight ice strike at liftoff or the condition of three suspect shuttle wing panels that prompted independent safety experts to call for replacements prior to launch.

In the post-Columbia era of the shuttle program, NASA had always kept a placeholder in the Flight Day 5 timeline for an additional inspection that might be required when the analyses of launch imagery and orbital inspection data raises questions about the intregrity of a shuttle's heat shield components.

NASA mission managers decided an extra inspection will not be required on Saturday.

The decision comes four days after a curved sheet of ice popped off a 17-inch propellant feedline on the shuttle's external tank when Discovery blasted off from Kennedy Space Center on Tuesday. Liftoff vibrations shook the ice loose and launch video shows it glanced off an umbilical door on the underside of the shuttle.

Four inches long, one-and-a-half-inches wide and about a half-inch thick, the ice sheet prompted NASA managers to send an inspection team out to the launch pad before clearing Discovery for flight.

The ice formed after more than 500,000 gallons of supercold liquid oxygen and liquid hydrogen -- the latter of which is Minus 423 degrees Fahrenheit -- was pumped into the 15-story fuel reservoir.

The ice began to melt as the heat of the day increased and countdown to a planned 11:38 a.m. launch continued.

NASA managers ultimately decided the ice would not pose a risk to fragile shuttle tiles that protect the spaceship and its crew from extreme heat -- 2,300 degrees Fahrenheit -- the orbiter's underside is exposed to during atmospheric reentry.

Mission managers nonetheless had to sign a waiver to Launch Commit Criteria because the ice sheet was larger than allowable under launch rules.

The decision also exonerated three suspect wing panels with slight defects in a coating designed to protect the thermal armor from oxidation -- normal wear and tear in orbital operations.

The defects prompted to NASA Engineering and Safety Center to recommend replacements prior to launch -- a move that would have resulted in 60-day delay in liftoff. The group -- formed in the aftermath of the 2003 Columbia accident -- was concerned that the coating loss could lead to a catastrophic burnthrough during reentry.

But NASA decided to press ahead with launch nonetheless.

Discovery's astronauts still plan one more inspection of the shuttle's wing panels and nosecap. The late inspection will come after the shuttle departs the station. It is designed to detect any micrometeoroid or orbital debris strikes that might occur while the shuttle is in space.

Discovery and its seven astronauts are due to reenter the atmosphere and land at Kennedy Space Center on Nov. 6.