Astronauts
aboard the International Space Station (ISS) are once more able to stage
spacewalks from their orbital laboratory after U.S. flight controllers cleared a
problematic handrail issue Thursday, NASA officials said.
NASA spokesperson
Kylie Clem said station managers lifted a month-long spacewalk ban aboard the
station, with a few conditions, after a pair of ISS flight and management meetings
today at the agency's Johnson Space Center (JSC) in Houston.
Defects
found in the station's aluminum handrails on the ground prompted ISS flight
controllers to hold all spacewalks in NASA's Extravehicular Mobility Unit (EMU) suits,
Kirk Shireman, the agency's deputy ISS program manager, said Wednesday.
"The
handrails can be used with a slight variation," Clem told SPACE.com,
adding that should a spacewalk be needed, astronauts would use a metal hook to
latch onto the stanchions that connect the rails to the station hull, rather
than the bar itself. "The analysis will continue to return to normal procedures
through mid-April."
No spacewalks
are currently scheduled for the space station's present crew, Expedition
12 commander Bill McArthur and flight engineer Valery Tokarev, but NASA flight
controllers wanted to resolve the issue should one be required in the event of
an emergency, NASA officials said.
Corrosion
on the aluminum handrail bars, which engineers traced back to improper heating
during their manufacture, led ISS officials to question the health of handrails
already installed on the space station's hull. Astronauts use the rails to
secure science experiments and themselves to the outpost's exterior, as well as
pull themselves between work stations.
"Our
suspicion is that it's very limited," Shireman said of the problem. "It was
difficult to say which of the handrails that are currently on orbit had this
material problem and which didn't."
Additional tests
to verify the long-term use of the U.S.-built handrails to hold material exposure
experiments are also scheduled for the future, he added.
Meanwhile,
four misplaced air scrubbers for the station crew's Russian-built Orlan spacesuits
have also impaired the astronaut's spacewalk capabilities, NASA said.
Additional
Orlan scrubbers - lithium hydroxide canisters that scrub carbon dioxide from
the spacesuit's atmosphere - have since been added to an unmanned Russian
Progress supply ship to launch spaceward in April. McArthur and Tokarev, who
are nearing the end of their six-month mission, will continue to search for the
missing Orlan canisters.
"We are
continuing to look for them and we believe we will locate them," Shireman said.
The two
astronauts have been packing their Soyuz TMA-7 spacecraft for their April 8 return
to Earth and will hand space station control over to their replacements, Expedition
13 commander Pavel Vinogradov and flight engineer Jeffrey Williams.
The
Expedition 13 crew and Brazilian
astronaut Marcos Pontes, an eight-day ISS visitor, will launch toward the
station atop a Russian-built Soyuz rocket from Baikonur Cosmodrome in
Kazakhstan on March 29 at 9:30 p.m. EST (0230 March 30 GMT).
The next
scheduled spacewalks outside the ISS are set during NASA's STS-121
shuttle mission, which is slated to launch on earlier than July 1. The
first dedicated Expedition 13 spacecraft is expected sometime after that
spaceflight, NASA officials said.
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