Space station computers still down after extensive troubleshooting session

Focus of Atlantis’ mission to the International Space Station is quickly turning to three critical Russian computers that have failed, resulting in what could be a potential unmanning of the station should problems not be fixed soon.

Carpenter Newton reporting for Digital Journal –– After several passes over Russian ground sites early this morning, three critical computers that control guidance, oxygen and water aboard the International Space Station were still not fixed. Late Thursday, space station resident Sunita Williams, her replacement, Clayton Anderson, and Russian cosmonaut Oleg Kotov used a signal analyzer to check power cables connected from the U.S. segment to the Russian segment. Nothing suspicious was found and Mission Control decided to completely disconnect power from the U.S. to Russian side and try to boot the computers using only Russian power. It has been suspected that installation of the S3/S4 solar array, conducted in a spacewalk on Monday, might be responsible for a subtle power change that may affect the computers. The three computers, built in Germany by Diamler-Benz several years ago, are known to be sensitive to what NASA is calling ‘noise’ and saying is like AM radio static. Mike Suffredini, space station program manager for NASA, used a voltage comparison to explain the problem at a Mission Status Briefing on Thursday. He stated that if the computers were rated for 15 volts -- plus or minus one volt -- and the power source was providing anything over the plus or minus one in addition to the 15, the computers could fail. While the ISS orbited over the Russian ground sites, engineers performed many of the same troubleshooting tasks they did on Thursday, this time with a different power source. Although there was some success yesterday communicating and restarting one of the computers -- which later went offline again -- there was no such luck today. Two of the computers powered up briefly but no communication took place. Following the unsuccessful troubleshooting, Russian cosmonauts put the space station back in the configuration it was yesterday, drawing power from the U.S. systems. The ground instructed the crew, who were up well into their sleep period, to get some rest while they constructed a different plan. While the systems are out on the ISS, space shuttle Atlantis is controlling the station’s attitude. Last night before STS-117 crew sleep, an extensive discussion took place with Mission Commander Frederick Sturckow about powering down systems on Atlantis in order to save cryogenic oxygen should the shuttle have to stay an extra day. Mission Control calculated that the shuttle was already in good configuration to have an extra day of oxygen but still ordered some lights and computers turned off. In a worst-case scenario, the International Space Station might have to be unmanned if the computer problems aren’t fixed by the time Atlantis has to return to Earth. Bill Gerstenmaier, NASA’s associate administrator for space operations, said, “We’re still a long way from where we would have to de-man the space station.” Third Spacewalk Later Today Preparations were well under way this morning to conduct the third spacewalk of STS-117. Astronauts James Reilly and Danny Olivas camped out overnight in the Quest airlock, a segment of the space station that has a reduced-nitrogen atmosphere. Spacewalkers have to spend the night in the airlock to purge excess nitrogen from their bloodstream to prevent decompression sickness (The Bends) while in space suits. The spacewalk is scheduled to start early this afternoon. After exiting the ISS, Reilly and Olivas will split up and work on separate tasks -- Reilly will install a vent on the station while Olivas will ride Atlantis’ robotic arm to the Orbital Maneuvering System pod and repair a damaged thermal blanket with surgical staples. After completing individual tasks, the men will meet at a disabled solar array that astronauts have been attempting to fold for two days. The array is currently folded halfway. Reilly and Olivas will use tools wrapped in insulating Kapton tape to help with the folding of the array. Should there be time left after the array fold, the spacewalkers will start several get ahead tasks before returning to the ISS.