Space station crew makes repairs Maintenance demonstrates need for caretakers in orbit

By James Oberg, NBC NEWS SPACE ANALYST

March 19 — Another breakdown and repair job aboard the international space station has underscored the importance of keeping a "caretaker" crew on board, even though the grounding of the space shuttle fleet means that assembly and science operations must be halted temporarily. And it accentuates the threats to the safe operation of the station as spare parts and supplies begin running low. The water pump in one of the Destiny science module’s two cooling loops failed early Sunday morning. An alternate loop took over the task of cooling the electronics equipment mounted throughout the module and in other nearby U.S. modules. The failure, which came within one more breakdown of forcing a shutdown of most of the electronic equipment on the U.S. section, absorbed most of the crew’s time on Sunday and Monday. After they had installed the replacement pump, station commander Ken Bowersox and chief science officer Don Pettit held off activating it until it could be checked out from the ground. "We’ve said all along that it’s always preferable never to ‘deman’ the station, for a variety of reasons," said Rob Navias, NASA spokesman in Houston. With a permanent crew presence, he explained, "You have real-time ability to respond in the event you need to repair something." "The power pump assembly was replaced with the spare," Navias told MSNBC.com today. "It was a fairly easy modular swapout." "It is now in the process of being retested," Navias said. "There is a lot of retesting that must be done to make sure you reconnect it right." After several hours of work on Tuesday morning, Bowersox and Pettit ran into what an official NASA status report delicately termed "an unexpected signature," and work was stopped. "Resolution of the problem is temporarily on hold," the NASA report stated. Further, the replacement unit itself reportedly has a leaky valve, but it can still function. "We’re OK as long as nothing else goes wrong," the source reported. Pettit had expressed concerns that the failed pump may have sent some "debris" into the water lines that could then damage the backup pump, but he was assured that the pump had screens to catch any such debris.

Restarting the pump was further delayed on Wednesday when software flaws in the station’s control computers disabled its stabilization control routines and began turning off scientific experiments. But by Thursday these problems were also repaired, and Navias was able to proudly announce the restart of the replaced coolant pump: "It’s up and running," he told msnbc.com late Thursday afternoon.

FAILURES ARE AN OPTION NASA

planners have always expected a facility as complex as the space station to have a "normal" failure rate for components, and the loss of the water pump is considered routine. What was unexpected was the need to perform such repairs while the delivery of spare parts and special tools would be severely constrained due to the absence of regular space shuttle missions.

At some point, some analysts have warned, the ability of the station’s crew to keep the station functioning may be so severely degraded that they will have to return to Earth and leave the station empty. Other equipment has also required significant tinkering by the crew, including the Russian Vozdukh carbon-dioxide scrubber; and the European-built Microgravity Science Glovebox, a research tool. The Russian unit requires frequent adjustments and repairs, but the latest failure last Friday was significant in that there were no longer any spares on board to fix a problem with a damaged power cable. The cable was removed, repaired, then reinstalled. More spare cables are slated for an unmanned supply flight early in June. The glovebox has been inoperable for months while Pettit has attempted numerous diagnostic tests. Equipment has been sent up on several supply flights, but to no avail. "Identification of the fault remains elusive," this week’s NASA status report noted. The pump failure was just another predictable repair task, experts say. "This is not an unusual circumstance," Navias stressed, describing how the crew and ground team responded in the past. "I’ve seen them react to other systems issues, from computers to cooling loops."

FINDING ROOM FOR SPARE PARTS

The malfunctioning coolant pump is fairly large, and there is no room for a replacement unit on scheduled supply missions through the end of the year. Navias said that Pettit would disassemble the unit to determine exactly which components had failed, so that replacement parts could then be sent up. A source told MSNBC.com that Pettit would probably need a new bearing set for the 16,000-rpm centrifugal pump, which had operated continuously for two and a half years before failing. "He’s a real garage-hound," Navias said of Pettit. "He loves to break out the toolbox." Once the exact items are identified, NASA will attempt to add them to the already-overloaded manifests of future Progress resupply missions. "We’ re taking a look," Navias told MSNBC.com. But internal NASA documents obtained by MSNBC.com show it will be a challenge to add new items to the next Russian supply mission, now scheduled for June 6. "Limited upmass capability of Russian vehicles may be further reduced by Russians," the document says. "Allocation is not sufficient to meet the mandatory NASA hardware requirements. ... There will not be enough water to last the entire [mission]." The document noted that only 44 pounds (20 kilograms) of the cargo has been allocated for U.S. needs. During the interval when the new pump installation was being verified, Mission Control threw together a contingency plan in case the other cooling loop’s pump failed as well. It would have required turning off most of the lab’s equipment and possibly even sending the entire space station into a slow, controlled "tumble" to balance heat exposure. "It’s another case of engineers doing their jobs, reacting to ‘what ifs’ once you get a hint that something curious has happened," one of the engineers told MSNBC.com. "Some folks in the press don’t seem to understand that this is what we do," he teased, referring to widespread media misunderstanding of "what-if" emails dealing with the Columbia wing damage.