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Monday, August 01, 2005

ABC News: Astronauts Work to Fix Station's Gyroscope

ABC News: Astronauts Work to Fix Station's GyroscopeAstronauts Work to Fix Station's Gyroscope
Discovery Astronauts Begin Spacewalk to Replace Gyroscope That Helps Steer Space Station
By PAM EASTON
The Associated Press

Aug. 1, 2005 - Two of Discovery's astronauts floated outside their spacecraft Monday with one key task: to replace a failed washing machine sized spinning wheel, which along with three other gyroscopes, helps to steer the international space station.

Astronauts Stephen Robinson and Soichi Noguchi planned to spend 6 1/2-hours exchanging the broken down 660-pound gyroscope, which failed in 2002, with a new one.

"Is it day or night out there?" Robinson asked minutes before the two opened the orbiting shuttle's airlock.

"You are going to be going out into the bright sun," astronaut Andrew Thomas told Robinson before telling Noguchi it was time to spacewalk.

"I will just push on your toes a little bit here," Robinson told his spacewalking partner as Noguchi exited the airlock over Asia. "Out you go."

Robinson followed.

Almost two hours later, the pair removed the faltered gyroscope.

Clutching the gyroscope with both gloved hands, Noguchi then hitched a ride to Discovery's cargo bay on the outpost's robotic arm. He planned to secure the faltered controller aboard the shuttle with Robinson's help and to retrieve the new gyroscope for installation.

"Oh, the view is priceless," Noguchi said during the ride. "I can see the moon."

During their first spacewalk Saturday, the pair restored power to another gyroscope, which had stopped spinning in March.

"Being outside was the most incredible experience I've certainly ever felt so far, and I almost can't believe we get to do it again," Robinson said Sunday as he prepared for his second orbital outing.

Only two of the four gyroscopes that control the orientation of the orbiting science lab have worked recently. Once power was restored to the third gyroscope Saturday, one of the two that continued spinning was given a break because its 6,600 revolutions per minute had become sluggish.

Once Discovery undocks from the station Saturday, NASA hopes to have all four gyroscopes operating simultaneously for the first time in three years.

On Sunday, NASA officials said they may consider repairing material dangling from Discovery's belly during a third spacewalk scheduled for Wednesday.

But there remains debate among engineers and others over how to handle what would be an unprecedented repair and whether it is even necessary.

Some engineers worry the filler that is protruding from between thermal tiles in two areas beneath the shuttle near its nose could trigger potentially treacherous overheating during re-entry.

NASA officials stressed that Discovery and its crew could be perfectly safe flying back with the exposed filler. Space shuttles have flown with exposed filler many times before, just not necessarily with such a large protrusion.

One piece is sticking out 1.1 inches. The other protrudes at an angle from six-tenths to nine-tenths of an inch. The general wisdom and flight history indicate that the limit should be a quarter-inch, said flight director Paul Hill

One solution would be to pull the filler completely out or fold it back in. Another could be to cut it, said Steve Poulos, manager of the orbiter project office.

Deputy shuttle program manager Wayne Hale said more technical information is needed and the risks of causing further damage by going underneath the shuttle need to be considered.

"We certainly don't want to make the situation worse than it is," he said. "My immediate knee-jerk reaction was that we can live with this. On the other hand, this is bigger than we have seen before."

In 24 years of shuttle flight, astronauts have never ventured beneath their spacecraft in orbit and have made few repairs to their ship.

But if NASA's spacewalking specialists can come up with an easy fix, Hale says correcting the problem may be worth eliminating concern about flying home with the protrusions.

"Why would you not just go take care of it?" he asked. "Why should I lose sleep over these gap fillers if we can take care of them that easy?"

The tools are aboard Discovery and the crew has already been trained how to cut the fillers, Poulos said. The filler keeps the shuttle's thermal tiles from damaging one another as the spacecraft heats up during re-entry and its protective thermal layer shifts.

Hale, however, said the analysis isn't complete.

"I certainly think the jury is out at this point as to whether or not we will do anything," he said.

On the Net:

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

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