NASA fine-tunes orbital rescue scenario

HOUSTON - Although NASA officials hope for a smooth flight of the space shuttle Discovery when it launches later this year, mission managers are still planning for the worst-case scenario.

A contingency plan that uses the international space station as a second home for Discovery’s seven crew members is in place, in the remote chance that the orbiter suffers critical damage and can’t return to Earth.

"We are still going to fly with some risk," said Wayne Hale, deputy director for NASA’s shuttle program, here at Johnson Space Center. "To characterize it otherwise would be inappropriate."

NASA has trained the crew of the follow-up to Discovery’s flight, the STS-121 mission aboard Atlantis, to be prepared to launch within 35 days of the start of a contingency plan. That rescue mission — which would then be called STS-300 instead — would fly up a reduced number of astronauts to pick up Discovery’s crew.

Risks remain
Hale said there is still a chance that foam insulation or other debris might strike the shuttle during future launches, though NASA officials have said they don’t expect chunks larger than marshmallows to fall off during liftoff.

A suitcase-sized chuck of external tank foam insulation doomed the Columbia mission and its seven-astronaut crew in 2003. The foam fell from Columbia’s external fuel tank at launch and damaged the orbiter’s left wing severely enough that the shuttle broke up during re-entry.

First things first: Discovery is currently set to launch no earlier than May 15, though delays in the shuttle’s delivery to its launch pad may push the date forward into a flight window that extends through June 3.

Discovery reached its launch pad early Thursday at the Kennedy Space Center in Florida after a slow crawl from the Vehicle Assembly Building that involved two minor delays. One of the delays was caused when a crack was discovered in the foam insulation of the external fuel tank. NASA officials said the crack was minor and would not prevent the planned liftoff.

This first shuttle to fly since Columbia, Discovery will carry the STS-114 mission crew on a station-bound spaceflight.

NASA redesigned the shuttle external tank for Discovery’s mission, though there were some concerns with the insulation this week.

Before the shuttle rolled out to its launch pad Wednesday, engineers found a small crack in the foam covering Discovery’s external tank. While no larger than a strand of hair, the crack did put a hold on Discovery’s roll out activities to allow time to photograph the area and relay the images to tank designers at NASA’s Michoud Processing Facility in Louisiana.

Michoud officials, however, said the crack was not a concern for launch and the shuttle later rolled out to the launch pad.

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