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[NASA] Spacewalk possibility

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vincent    154
Protuding fabric may lead NASA to schedule spacewalk

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This photo provided by NASA shows the shuttle's underside near the nose landing-gear door. Fabric pieces (not visible) protruding near the door are of concern

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This photo taken from the international space station and provided by NASA shows the top of Discovery just before it docked at the station Thursday.

HOUSTON ? While most of the surface damage on the space shuttle Discovery has been deemed safe, concern over two protruding pieces of a heat-resistant fabric on the underside of the craft is causing NASA to consider a first-ever spacewalk to make a major shuttle repair, officials said yesterday.

Paul Hill, the lead flight director for the 114th shuttle mission, said an engineering team is expected to have a recommendation today on whether an astronaut will be sent out with a hacksaw to trim off the fabric, known as a "gap filler."

"We have viewed the options from pulling the gap fillers out to trimming the gap fillers to putting [them] back down into the gap," Hill said.

Thousands of gap fillers, made of a flexible, ceramic-coated material about as thick as a credit card, are placed between the heat-resistant tiles covering the shuttle. Two of them near Discovery's front landing-gear door are sticking out as much 1.1 inches, well beyond the quarter-inch allowed by engineers.

The concern is that even a small protrusion could disrupt air flow under the extreme conditions of re-entry, increasing the heating just behind the protrusions by almost 600 degrees. That could be hot enough to threaten the integrity of tiles protecting the spacecraft.

Protruding gap fillers have been observed on previous flights but always after the shuttle had landed. This time, dozens of new sensors and cameras installed after the destruction of the space shuttle Columbia on re-entry two years ago have allowed engineers to see damage while the shuttle is in orbit.

If National Aeronautics and Space Administration managers decide to fix the problem, an astronaut would have to be carried on either Discovery's or the international space station's robotic arm to the underside of the shuttle, where the damage is.

The repair itself should not be difficult. Because the gap fillers are bonded to the vehicle with glue, they could be pulled out.

The problem is no spacewalk is completely safe. This one was not practiced during the years the crew trained for the mission, although Discover does carry "EVA scissors," a special hacksaw-like device provided for just such a situation.

Engineers and specialists in aerodynamics are working overtime to come up with a recommendation. "They're pressing decades of study into two days," said deputy shuttle program manager, Wayne Hale.

The protruding gap fillers are in a particularly sensitive area near Discovery's front landing-gear door. Temperatures can reach 2,300 degrees Fahrenheit as the craft uses the Earth's atmosphere to brake from 17,500 mph to a safe landing speed.

The silica tiles that cover most of the aircraft are not designed to accept the worst heating, which is why the nose and leading edges of the wings are covered with expensive reinforced carbon panels.

The engineers could well decide to leave the craft as is. "My immediate reaction is, we can live with this," Hale said.

But if the engineers are unable to assure him there would be no dangerous excess heating, the management team might decide to err on the side of caution and fix the problem.

The flight of Discovery has been dogged by a series of problems, beginning the day of launch, when a large piece of foam fell off the external fuel tank.

Even though the foam missed hitting Discovery, NASA quickly grounded the shuttle fleet pending a solution of the problem.

In the succeeding days, one problem after another, from tile damage to blemishes on the reinforced carbon panels, have raised concerns. Each one was ultimately found to be no threat to the vehicle.

The new sensors and imagers on Discovery have "put the orbiter thermal-protection system under a microscope," Hale said.

While NASA managers on the ground debated what to do about the gap fillers, Discovery commander Eileen Collins and her crew said in TV interviews yesterday that they believe Discovery is safe to come home.

Collins expressed surprise and disappointment that a big piece of foam came off Discovery's redesigned tank during last Tuesday's liftoff, after everyone ? including herself ? signed off on analysis showing that the specific area did not need to be improved after the Columbia tragedy.

"Was there a sound technical reason why they made that decision or was it subject to cost pressures or schedule pressures?" said astronaut Andrew Thomas. "I think we do need to address the question of why that area was not examined."

Both Collins and NASA Administrator Michael Griffin said the decision not to retrofit the area was based on X-ray and other noninvasive testing that found nothing suspicious.

Seattletimes.com

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GNRambo    0

Havent they done a 7 hour space walk already? :s

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Deathray    4
Havent they done a 7 hour space walk already? :s

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Difference with this is it will be a shuttle repair, never done before... Should be interesting. Especially on the underside :s...

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strekship    16

Hopefully they can get it all sorted out and return home safely.

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gam_EZ    28
Difference with this is it will be a shuttle repair, never done before... Should be interesting. Especially on the underside :s...

586310520[/snapback]

I second that...there has been enough disaster with space missions :(

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Nashy    1,661

NASA needs to sort their crap out rather than risking 7 people's lives just to get back into space.

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