Station crew awaits spare parts for air scrubber
BY WILLIAM HARWOOD
Posted: December 16, 2000
As a result, U.S. and Russian managers are refining plans to launch spare parts for the station's air conditioner and its regenerative carbon dioxide removal system aboard the shuttle Atlantis next month and/or a Progress supply ship scheduled for launch in mid February.
In the meantime, if the station's Russian-built Vozdukh carbon dioxide scrubber breaks down and cannot be repaired, the three-man crew would be forced to use canisters of lithium hydroxide to scrub the station's air supply.
But there is only enough lithium hydroxide on board to last the crew 14 days. If the Vozdukh failed and could not be repaired, commander William Shepherd, Yuri Gidzenko and Sergei Krikalev likely would be forced to abandon ship and return to Earth aboard their Soyuz ferry craft.
No one expects that scenario to actually play out and lead flight director Jeff Hanley told reporters Friday the Vozdukh currently is operating flawlessly. But he agreed the crew is one failure away from a potential bailout.
"At some point, that's true," he said. "That's the capability we have in place."
The Vozdukh's original microcompressor fan assembly, which forces the cabin air over a bed of chemicals that absorbs carbon dioxide, broke down shortly after the unit was activated. A backup fan assembly was installed, but a bad electrical connector forced the crew to replace it with a third and final backup.
That unit is operating normally and there are no more spares on board.
Hanley said the fan with the bad electrical connector possibly could be repaired by the crew if it came down to that, but NASA is not taking any chances.
A spare power supply for the station's one functioning air conditioner and parts for the Vozdukh - possibly even a complete unit - will be ferried into orbit aboard Atlantis, scheduled for launch Jan. 18, or the next Progress supply ship, currently targeted for takeoff Feb. 10.
"We never had more than about 14 days of (lithium hydroxide) capability, 14 to 21 days," Hanley said. "That was because the Vozdukh system had a good long heritage, we had spare parts available. We had two spare microcompressor units on board. We've had to play all those cards to have an operational system. We weren't counting on multiple failures."
The Progress M1-4 vehicle was launched Nov. 16 and docked to the Zarya module's Earth-facing nadir port two days later. It was undocked Dec. 1 and moved into a nearby parking orbit to make room for the shuttle Endeavour, which docked to the nearby nadir port of the Unity module the next day.
During the M1-4 vehicle's initial docking attempt Nov. 18, the KURS automatic guidance system failed, forcing Gidzenko to remotely pilot the unmanned craft to a linkup with the station using the manual TORU system. Russian engineers later traced the KURS failure to a software glitch and developed a "patch" to correct the problem.
But the KURS system, even if it works, can only bring the Progress M1-4 spacecraft to a point 200 meters from the station. That's because a KURS antenna needed for the final push to docking was retracted before the first docking attempt and it was not designed to be re-extended.
From 200 meters in, Gidzenko will once again have to manually pilot the craft using camera views and a joystick hand controller.
Hanley and other senior managers originally said they would not support a redocking because the manual TORU system has no backup. But as it turns out, Hanley said Friday, it does. If the Progress lost contact with the TORU signal from the station, for example, it would automatically abort its approach.
In other words, Gidzenko could simply turn the system off if things got out of hand and the Progress would back away from the station.
"The current proposal on the table is to perform the redocking on the 26th of December," Hanley said. "The preliminary docking time is about 11 GMT followed by orbital sunset a couple of minutes later. This gives us good lighting during the approach and docking over Russian ground sites."
The Progress M1-4 will redock at Zarya's Earth-facing nadir port. After Atlantis's upcoming mission, the Progress will be jettisoned and the crew's Soyuz ferry craft, currently docked to the aft port of the Zvezeda command module, will be moved to Zarya's nadir port. The third Progress, scheduled for launch Feb. 10, will dock at Zvezda's aft port.
The M1-4 vehicle's redocking is expected to be approved and NASA plans to provide live television coverage starting about 90 minutes before contact.
"The current plan is still under review by the team," Hanley said. "We believe that by this time next week, the entire management team will have reached a final decision."
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