HOUSTON--While STS-114
spacewalker Stephen Robinson will be working alone during a one-man
repair job underneath the shuttle Discovery Wednesday, he will not be out
of sight or the minds of his fellow crewmates and flight controllers, the
astronauts and shuttle officials said today.
As
part of a planned extravehicular
activity (EVA) tomorrow, Robinson is expected to board the end of a long
robotic arm and remove two strips of ceramic fiber cloth--known as
gap-filler--jutting out from between the fragile heat-resistant tiles along
Discovery's belly. The repair is scheduled to take place at about 7:30 a.m. EDT
(1130 GMT), three hours and 20 minutes into the early morning spacewalk,
shuttle officials said.
"At
the highlight of the EVA, when Steve is removing the gap-filler, we're all
going to be listening very intently," STS-114 commander Eileen Collins told
reporters vie video downlink earlier today.
During
the fix, Robinson's fellow Discovery astronauts will track his movements via
robot-arm mounted cameras radio while his spacewalking partner Soichi Noguchi, of the Japanese Aerospace Exploration
Agency (JAXA), will keep close watch on the operation from a vantage point
outside the ISS.
"He's
there to give us another set of eyes and also serve as relay [for
communications] if needed," said Kelly Beck, flight director of NASA's Tiger
Team assigned to hammer out procedures for changes in Discovery's flight plan,
during a mission status report here at Johnson Space Center (JSC).
Shuttle
officials decided Monday to press forward with the spacewalk repair to clear
any concerns with Discovery's vital heat shield. The protruding gap-fillers
could disrupt the aerodynamics of Discovery's reentry planned for Aug. 8,
forcing the air around the orbiter to shift from the smooth laminar flow into a
turbulent mix a bit earlier in the descent, while it flies at Mach 21 as
opposed to Mach 18 or so, that could cause increase heating to its tile surface
and wing leading edges, they said then.
During
the repair, Robinson will stand atop the robotic arm attached to the International
Space Station (ISS), while Discovery's crew maneuvers the shuttle's robotic arm
- capped with an orbital boom extension to make a 100-foot crane - to watch
with its own camera.
"They're
not used to reaching down around the bottom of the orbiter," said Paul Hill,
STS-114's lead shuttle flight director, of ISS arm controllers for the
first-time repair job. "That's a little bit of a new touch."
Spacewalk
planners are unsure whether Robinson helmet mounted camera will be able to
broadcast images of the fix as the astronaut first uses his right hand to pull
out the gap-fillers, and then a saw to cut them off if they don't budge.
Discovery
astronauts and flight controllers agree that the removal technique for the
gap-fillers, a simple tugging motion by hand, is relatively simple, but they
are concerned about potentially damaging the shuttle's tile-lined belly.
"We
may get a little closer than a foot [from the tile], but when we do we'll have
very good visibility and we'll be moving very slowly," said astronaut David
Wolf, head of the EVA branch of NASA's Astronaut Office. "We don't like getting
close to the tile, [it] is a delicate instrument of
the shuttle."
Robinson
will take care not to bump his helmet, the most probably point of impact, on
the shuttle's vulnerable tiles, Wolf added.
Spacewalk
officials are confident that should a gentle touch or slip from Robinson's
secondary tool - the modified hack saw - does cause tile damage, it will be
relatively minor. But just in case, Robinson and Noguchi will preposition a
tile repair method they tested in an earlier spacewalk - an emittance
wash applicator that coats chipped tiles to increase heat shedding - just
outside the shuttle airlock, which could be applied to any damage caused,
shuttle officials said.
"When
we went to look at this, we had difficulty even inducing intentional tile
damage with the saw," Wolf said. "And you'd be able to detect when you're
hitting the orbiter will before you do a critical damage."
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