NASA helps review space station failure

Post-mortem aimed at avoiding shutdowns

Photo by NASA

Engineers from NASA and the Russian space agency have formed a team to analyze the recent IT malfunction on the International Space Station that jeopardized the missions of the inhabited orbiting platform and the attached shuttle Atlantis.

Three critical computers failed during the incident, which disabled the station's steering control systems and shut down its air and water production equipment.

The space station's crew retained the ability to keep the craft pointed correctly in the direction of the sun to capture light needed to operate photovoltaic panels, officials said.

That backup capability relied partly on gyroscopes installed in the NASA-built section of the space station to stabilize the platform and partly on the thrusters carried by the docked Atlantis.

The crew's water and air supplies also were in no immediate danger, the agency said.

The three computers, built by Daimler-Benz of Germany and supplied to the station as part of its Russian-built segment, lost power during the incident, NASA said.

The station's crew responded with an around-the-clock troubleshooting and repair campaign June 14 and 15 that focused on the power sources linked to the computers, according to NASA reports.

One of the goals was to detect variations in line voltage and power quality that could have triggered the computer shutdown, according to NASA.

If the computer shutdown had continued for an extended period, the problem could have forced officials to lengthen Atlantis' mission at the space station, NASA said. The incident did raise the remote possibility that the entire space station would have failed, the agency said.

But the crew's troubleshooting work and patchwork repairs saved the day, according to NASA mission status reports and briefings.

With the assistance of ground-based engineers, 'Station Commander Fyodor Yurchikhin and Flight Engineer Oleg Kotov were able to re-enable four of the six channels in the computer systems after bypassing what appears to be a faulty power switch with external cabling,' according to ISS program manager Michael Suffredini.
Suffredini spoke June 16 at a briefing at NASA's Johnson Space Flight Center in Houston.

The next day a NASA mission update stated, 'the Russian central computer and terminal computers continue in stable operation, each running on two of its three channels with the third in standby.'

Following the initial success of the computer repair efforts, the space station crew followed a test procedure specially developed to assure that the fix would continue to work.

The test protocol called for a Tinker-to-Evers-to-Chance relay of the space station's steering control from the shuttle thrusters, to the ISS thrusters and finally to the gyroscopes that normally maintain the craft in its proper position.

The Russian computers that had failed during the mission were responsible for the successive handoffs of control function during the four-hour test, NASA said.

If the test had failed, ISS program leaders would have directed that Atlantis remain docked with the space station for an additional day of troubleshooting. The test's success cleared the way for Atlantis' return trip to begin on June 19.

As for taking steps to prevent any additional computer failures, a NASA spokeswoman said in an e-mail statement, 'NASA and our Russian colleagues did form a team to investigate the root cause of the computer problems. The team is tasked with analyzing the data and developing a systematic approach to isolating and repairing the problem.'

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