Astronauts Find Metal Shavings Under Space Station's Hood

ByGina Sunseri
January 08, 2009, 1:08 AM

Oct. 28, 2007 — -- Engineers are working through the night to analyze the photographs of shavings found in the malfunctioning solar array rotating joint on the starboard side of the International Space Station.

What does this mean for the space station if it is not fixed?

Mike Suffredini, space station program manager, says this problem has the potential to prevent extending the life of the space station past 2015. It was discovered that the solar array was vibrating, which, Suffredini says, has an effect on the fatigue life of the structure.

Suffredini added, however, that dealing with this problem is just another day in the life of maintaining an orbiting outpost like the space station.

Anyone who has worked on motors can understand what it meant when astronaut Dan Tani, during a spacewalk, took the cover off the solar array rotating joint on the starboard array, and found tiny metal shavings. Lots and lots of tiny metal shavings. "It's quite clear," Tani told Mission Control, "there is metal to metal scraping, and it's widespread. Wow."

NASA added this task to the second spacewalk of the STS 120 mission, because engineers were worried about the vibrations they were seeing on this joint. It allows the solar arrays to track the sun for maximum power generation.

One night a couple of months ago, Rob Adams, an engineer in the mission evaluation room of Mission Control was staring intently at the camera view of the starboard solar array, when he thought he saw it vibrate. He noted it, according to Kirk Shireman, deputy program manager for the space station.

Engineers hoped it was just the camera vibrating. It wasn't that simple. The whole engine was vibrating and drawing more power than normal, which was sending a ripple down the array.

The malfunction isn't an immediate problem. Flight director Derek Hassman says it is easy to just angle the array for maximum exposure and then park it. But NASA needs to know if this is a design problem. So, flight planners decided to send the spacewalkers on a detour by the rotating joint to take a look at it.

Tani took a sample of the metal filings with a piece of tape, and engineers will examine the sample when the Space Shuttle Discovery returns to Earth next week.

The SARJ is a 10-foot-wide rotary joint that weighs 2,500 pounds. There is one on the starboard side of the space station, and one on the port side. Their function is to move the solar arrays 360 degrees, like a Ferris wheel, once per obit, as the space station circles Earth.

The part in question was installed this past June, and if it is failing, engineers would need to fix it, or at least understand what is happening, before the critical sequence of installation on the space station continues with the next shuttle launch — STS 122. The space shuttle Atlantis is scheduled to take off December 6 to deliver the European module Columbus to the space station.

But it wasn't all work on the spacewalk. Tani took some time to admire the view. "I see O'Hare Airport, and I can make out my hometown of Lombard."

Three more spacewalks are scheduled before this mission ends, and flight directors are considering sending the astronauts out to take another look at the troublesome joint.

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