HOUSTON — As the crew of the international space station prepare for an unscheduled repair spacewalk on June 10 they are being bedeviled by a series of small breakdowns that vividly demonstrate how rickety the station is getting without the constant flow of replacement parts that only space shuttles can provide.
Cosmonaut Gennady Padalka and astronaut Michael Fincke are set to practice on Wednesday getting into U.S. spacesuits without the aid of a third crewmember as assistant. The two are using the suits and air lock in the U.S. module of the space station because it is closer to the breakdown they intend to fix: a gyroscope that malfunctioned within days of the two men's arrival on the station last month. The gyroscope is easily accessible from the "Quest" air lock but would be a grueling, hazardous hand-over-hand traverse from the Russian "Pirs" module’s air lock.
The men will also use general-purpose spacesuit gloves instead of the form-fitted ones designed for their individual hands. Aside from the loss of flexibility in the non-personalized gloves, using them means extra stress on hand muscles. Their personal gloves are being sent up on a robot supply ship shortly.
Preparations for the spacewalk have also been hampered by failed batteries for their power tools, failed battery chargers for the rest of their suit equipment, failed lighting fixtures in the airlock, failed biomedical sensors and, most recently, the realization that their original repair plan wouldn’t work.
A NASA internal station status report announced this discovery on May 13. “For replacing the failed RPCM (remote power controller module) during the EVA on 6/10, the power assembly SPDA (secondary power distribution assembly) on the port side must be accessed,” reads the report, which was obtained by MSNBC.com. “An issue has come up with structural interference between the SPDA door and the Node 2 fluid umbilical tray, which prevents the door from opening enough to complete the RPCM replacement.”
It turns out that this interference was already known, but the report explains that it “was not corrected on the ground since the analysis focused only on the ‘ISS Complete’ configuration, i.e., with Node 2 installed.”
In other words, the assessments for in-flight maintenance assumed the gyro would not break until after the modules had been rearranged. And if station assembly had continued as originally planned, they would have been at this point.
But the loss of the space shuttle Columbia in 2003 halted U.S. shuttle missions, and with them, station assembly. The awkwardness of repairing this subsequent breakdown is yet another trickle-down consequence of the current assembly hiatus.
The report continues: “Clearing the interference (by removing launch restraint bolts on the fluid umbilical structure and a stanchion bolt [partially] to allow the tray to be pulled enough [~1 inch] out of the way for the door to slide open) may greatly change EVA content and timeline,” the report continued. “Investigation continues, and the uplink of the complete EVA timeline procedures scheduled for yesterday was deferred until necessary steps to resolve the issue are defined.”
Space station timelineIn the days that followed, a procedure to move the interfering hardware was developed. A NASA source who requested anonymity told MSNBC.com that “accessing the failed RPCM may now require the crew to remove Node 2 fluid umbilical tray for access to the SPDA door.” But the good news is that it’s “not a big hit to the timeline, if the [power tool] issues can be resolved.”
The power tool designed to remove restraining bolts had not been used in more than a year, and its batteries were in a full discharge state. For a week, the station crew repeatedly tried and failed to charge them. But after much effort, two compatible batteries were found that did take and hold a charge. The alternative –- using a manual ratchet wrench -– would have added an hour or more to the spacewalk.
The extra work may stress the spacewalkers beyond the expected level, and controllers remember how a cooling system malfunction in a Russian suit on the last spacewalk required an early termination . For this spacewalk, people on the ground may have to monitor the crew’s medical status "in the blind," because the biomedical instrumentation for the suits has failed.
“The Russian Flight Surgeons are insisting that Padalka have an operating biomed,” the NASA source said. The issue is that the wiring may constitute a shock hazard to the suit’s occupant, and safety officials have been unable to verify that it won’t. However, they have the ability to waive that concern, and the biomedical equipment will be tested during the upcoming dry run. If there are problems with it, or the suits, then the decision may be made to switch to the new Russian suits.
The crew must also find time for some repairs to the U.S. air lock itself. On May 14, an internal NASA status report noted that “a lighting fixture (LHA, lamp housing assembly) in the A/L Equipment Lock (E/L) will have to be replaced with an LHA scavenged from the Lab module. Mike Fincke was asked to name his preference on which LHA to use. [In the adjacent A/L Crew Lock (C/L) there is currently only one lighting fixture working, and in the Lab two LHAs are failed (or blinking).]”
“Yes, this EVA has presented an interesting set of issues to resolve,” said the NASA source. “So far, none are show stoppers.
“If all goes well,” he continued, “then we're out the hatch on 6/10. If not, ....”