A curved sheet of ice that popped off Discovery's external tank at liftoff glanced off an umbilical door on the underside of the orbiter and did no serious damage to shuttle heat-shield tiles or a critical door seal, a senior NASA manager said.
John Shannon, chairman of NASA's Mission Management Team, compared the event to dropping an ice cube onto something from a height of about 10 inches. Such a drop could not generate enough force to do significant damage, he said.
"It was just an incredibly minimal grazing of that surface," said Shannon, deputy manager of NASA's shuttle program.
Four inches long, one-and-a-half inches wide and about a half-inch thick, the sheet of ice formed on a 17-inch propellant feedline after the shuttle's 15-story tank was filled with more than 500,000 gallons of supercold liquid oxygen and liquid hydrogen, the latter of which is Minus 423 degrees Fahrenheit.
NASA officials initially were concerned that the ice sheet might cause damage to shuttle heat shield tiles but decided to launch after analyses showed it likely would break free right at liftoff.
Discovery's astronauts were given a heads up in a message that was beamed up to the crew early today. You can check it out here: MSG019.pdf.
Shannon also said that the ongoing review of launch imagery and orbital inspection data to date indicates that no serious damage was done to either shuttle tiles, the orbiter's nose cap or the carbon carbon panels that serve as thermal armor for the spaceship's delta-shaped wings.
"So far, so good," Shannon said. "It's a pretty clean vehicle."
The review is expected to be complete with the next 48 hours.
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