Engineers troubleshoot station computer problem
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 11, 2007
A U.S. command-and-control computer, one of three in charge of critical functions on the international space station, unexpectedly shut down today at 3:52 p.m. A backup C&C computer immediately took over and a third computer that was in standby mode reconfigured itself to serve as a "hot backup" in case of additional problems.
"The backup computer immediately kicked in and took over the functions of the primary computer and also the third computer in line, which is essentially a computer that remains in standby, that computer transitioned into the backup mode," said mission control commentator Kyle Herring. "So two of the three command-and-control computers are working just fine and there's no implication for the spacewalk or the health of the station right now."
Space station engineers are studying telemetry to figure out what happened, "but again, the backup did exactly what it was supposed to do and it took over the command-and-control functions," Herring said.
The computers are located in the U.S. Destiny laboratory module. Known as command-and-control computers, or C&C MDMs, the machines oversee the operation of the station's stabilizing gyroscopes, its high-speed communications links with Earth, the station's robot arm and other critical systems.
Each computer uses an internal hard drive to store programs and system software. Only one computer is in control at any given moment with a second serving as a hot backup and the third in standby.
During shuttle mission STS-100 in April 2001, C&C-1 suddenly dropped off line because of a hard drive problem and C&C-2, which was the backup machine, switched to primary mode. It, too, experienced hard drive errors and flight controllers decided to call up C&C-3. That computer promptly failed.
After five days of troubleshooting, engineers concluded a hard drive problem with C&C-2 was a known issue and not an outright failure. The other two computers apparently were the victims of unlikely, near-simultaneous failures of two critical hard drives."
Last June, during shuttle mission STS-117, the Russian segment's three C&C computers, along with three guidance and navigation computers, crashed after the attachment of the S4 solar array truss. The computers were recovered after commander Fyodor Yurchikhin and Oleg Kotov bypassed suspect secondary power supply surge circuitry.
Coincidentally, today's U.S. computer glitch happened while Yurchikhin and Kotov were gearing up to begin a complex 28-hour repair job to replace corroded cables leading to a computer processing unit known as BOK-3 that may have played a role in the June failures.
Spacewalkers Rick Mastracchio and Dave Williams, meanwhile, are pressing ahead with their planned six-and-a-half-hour spacewalk. They have successfully attached the S5 solar array truss segment to the right side of the station's power truss and are wrapping up a few get-ahead tasks before moving up to the central Z1 truss to lock down a cooling radiator. As of 4 p.m., the spacewalk was running about 10 minutes ahead of schedule.