NASA clears Discovery to return to Earth

The astronauts gathered batteries, laptops and the tethers that secured them during spacewalks.

But the biggest task before leaving the station was to maneuver a huge cargo container filled with 2 1/2-years worth of trash and other items from the station into the shuttle’s payload bay — essentially the spacecraft’s trunk. Once back on Earth, the items would either be disposed of or returned to researchers.

Much of Friday’s work was tedious and time-consuming. At one point, astronauts asked Mission Control what they should do with a piece of white foam that wouldn’t fit into a bag.

“We see it well, and we concur. It is not tiny,” Mission Control’s Steve Frick said after looking at the material over a video link. He later told the crew they could cut the foam to make it fit.

Another call from Mission Control went unanswered for a few minutes as the astronauts worked. “Sorry to ignore you,” astronaut Stephen Robinson radioed as the crew secured items in large white bags. “We all have our heads down in bags.”

Friday’s activity came a day after NASA gave the all-clear for Discovery to return to Earth, concluding that there was no need to send the astronauts out on another spacewalk to repair a torn thermal blanket near a cockpit window.

Mission managers could not guarantee that a piece of the blanket wouldn’t rip and slam into the spacecraft during re-entry, but said the chances were remote.

“We have assessed the risk to the very best of our engineering knowledge and we believe that it is remote, small, whatever adjective you want to put with that,” deputy shuttle program manager Wayne Hale said. “And the remedy that might be called for to try to make this better would be worse.”

Had the astronauts been asked to repair the blanket, it would have been the fourth spacewalk of the 13-day mission. It also would have been the second time during the flight that the astronauts had to step outside to repair the shuttle’s thermal protection system.

During unprecedented repairs to the spacecraft earlier this week, astronaut Stephen Robinson went beneath Discovery’s belly to remove two protruding strips of tile filler that engineers thought could lead to dangerous overheating during the trip home.

They feared leaving the strips could cause a repeat of Columbia’s disastrous re-entry in 2003 when that spacecraft broke apart over Texas as it headed to Florida.

Columbia was doomed by a 1.67-pound piece of insulating foam that fell from its external tank during launch. The foam pierced a hole in the spacecraft’s left wing and as it re-entered the Earth’s atmosphere, searing gases melted the wing from the inside out causing the ship to break apart. The seven astronauts on board were killed.

Discovery is the first shuttle to return to orbit since the tragedy.

Among its crew’s goals were the resupply of the space station, bringing home the station’s trash and intense inspections of Discovery for damage. The astronauts also tested repair techniques on orbit that were developed after Columbia.

“We put the orbiter under a microscope,” Hale said of Discovery. “We are out there with every little spot, scuff, ding, you name it. It’s not ignored. It’s not brushed off. It is evaluated by a large team of engineers who are very knowledgeable.”

Some critics might say a lot seems to be wrong with Discovery, Hale said.

“If we were not to tell you about this stuff, then I feel like we would get in trouble the other way,” Hale said. “We want to be very open.”

Shortly after Discovery’s launch, NASA officials learned a large chunk of foam reminiscent of the one that doomed Columbia had fallen from Discovery’s external tank during its climb to orbit. NASA quickly said it would ground future missions until it can find a way to keep large pieces of debris from shedding.

The agency has already spent $1.4 billion and 2 1/2-years working on the problem.

“I think we have said it before and I’ll say it one more time, we missed something here,” Hale said. “That has got to be rectified before we fly again.”

Discovery is set to undock from the space station Saturday. The crews planned one last meal together before Discovery’s departure from the orbiting lab.

The shuttle is scheduled to land back at Cape Canaveral, Fla., before dawn on Monday.

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On the Net:

NASA: http://www.nasa.gov/returntoflight/main/index.html