Uh Oh..Astronauts Discover Damage to Space Station

[SoCalDem]

http://www.nytimes.com/2007/10/29/science/space/29shuttle.html?_r=1&hp&oref=slogin

Astronauts Discover Damage to Space Station


By JOHN SCHWARTZ
Published: October 29, 2007

Spacewalking astronauts yesterday found evidence of damage to a crucial part of the International Space Station’s power system.
The discovery of what appear to be metallic shavings in one of the station’s enormous rotating joint assemblies suggested problems for the orbiting space station that could affect ambitious plans to add two power-hungry laboratories.

The problem was found during the second of five scheduled spacewalks of the space shuttle Discovery’s current mission. The astronauts Scott E. Parazynski and Daniel M. Tani unbuckled a solar array atop the space station so it could be relocated and made progress on outfitting the exterior of the station’s newest room, the Harmony module.

The part in question, known as the Solar Alpha Rotary Joint, or SARJ, is 10 feet across; one sits toward each end of the station’s long truss. The motorized joint allows solar panels to rotate and constantly face the sun during the sunny part of each orbit.“It’s quite clear,” said Mr. Tani, describing what he saw after removing a protective cover over an assembly of gears and bearings. “There’s metal-to-metal scraping, or something, and it’s widespread.” Mr. Tani collected some of the material with tape.

A sharp-eyed space station flight controller had noticed several weeks ago that the joint on the right side of the station was experiencing unusual vibrations as it rotated.

Further examination revealed that the motor on that joint was using greater-than-expected amounts of current, which suggested that it was having to work harder than it should to turn the 30,000-pound paddle wheel-like array. So on Friday, mission managers added the inspection to the spacewalk.

snip