An unmanned Russian Progress cargo ship, loaded with computer replacement gear, propellant and other needed supplies, docked with the international space station today. The Progress 26P spacecraft, launched Aug. 2 from the Baikonur Cosmodrome in Kazakhstan, engaged the docking mechanism on the downward facing Pirs airlock module at 2:40 p.m. EDT.

The cargo ship is loaded with 5,111 pounds of wet and dry cargo, including 1,587 pounds of propellant; 107 pounds of oxygen; 463 pounds of water; and 2,954 pounds of dry cargo. The latter includes computer replacement gear that will be installed over a four-day period during the shuttle Endeavour's upcoming visit to attach a new solar array truss segment and other equipment.

During a shuttle visit in June, the three computers making up the Russian segment's guidance and navigation system, along with all three "lanes" making up the Russian command and control computer system, crashed because of apparent problems with secondary power supply surge protectors. The computers were coaxed back into operation after station commander Fyodor Yurchikhin and flight engineer Oleg Kotov installed jumpers to bypass the suspect power supply circuitry.

A later inspection revealed widespread corrosion on computer cable connectors at a critical electronics box located near an air conditioner in the Zvezda command module. Russian engineers believe the corrosion played a role in the computer crashes.

"We're continuing to try to fully understand what caused this problem," Kirk Shireman, deputy manager of the space station program at the Johnson Space Center in Houston, said last month. "The debugging has looked at not only the computers, but looking at all the command string, if you will. The commands that come to these computers fall through a number of hardware devices along the way.

"We had some anomalous readings on some cables and also a box upstream of the computers called the BOK-3. If you look at the BOK-3 itself, it also looks like it has some corrosion on that box."

The box and cabling will be replaced by Yurchikhin and Kotov over a four-day period during the shuttle Endeavour's upcoming visit. All in all, some 28 hours of crew time will be needed to complete the repair job.

"We believe we can execute 118 (Endeavour's mission) in the current configuration with no limitation," Shireman said.

Engineers initially believed the computer problems might have been caused by subtle changes in the space station's electrical grid due to the attachment of a new set of solar arrays by the visiting shuttle astronauts.

"At this point in time, it's looking like that was not the cause," Shireman said. "But absolutely, we're very suspicious of coincidences so we're continuing to pursue it."

Additional coverage for subscribers:
VIDEO: PROGRESS 26P DOCKS TO THE STATION PLAY
VIDEO: SUNDAY COUNTDOWN AND WEATHER UPDATE PLAY
VIDEO: CREW ARRIVES AT KENNEDY SPACE CENTER PLAY
VIDEO: COMMENTS FROM EACH OF THE ASTRONAUTS PLAY
MORE: STS-118 VIDEO COVERAGE
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