HOUSTON - As shuttle managers debate
whether an untried repair is needed to pry two space-filling strips from the
underside of the Discovery orbiter, spacewalk planners have chosen which
astronaut would perform the potential task, the mission's lead spacewalk
officer said.
Shuttle astronaut Stephen Robinson,
mission specialist and flight engineer for Discovery's STS-114 spaceflight,
would perform the repair as part of a planned Aug. 3 spacewalk if mission
managers decide it is necessary later today, said Cindy Begley, the flight's
lead extravehicular (EVA) officer.
Discovery's mission management team
(MMT) convened at 2:00 p.m. EDT (1800 GMT) here at NASA's Johnson Space Center
(JSC) to go over final data and decide whether to remove two gap-fillers
jutting out from between the heat tiles lining the shuttle's forward section or
leave them as is.
"We don't currently have directions
to do [the repair] but as always we try to get all our ducks in a row ahead of
time," Begley said. "Something we've never been done before is put a crewmember
underneath the vehicle."
Shuttle tile gap-fillers are small
strips of ceramic fiber cloth glued between the orbiter's heat-resistant tiles
to fill excess space. Orbital
photographs and a subsequent focused
inspection detected two gap-fillers jutting out; one sticking 1.1 inches
(2.7 centimeters) out of a region just behind Discovery's nose landing gear
doors and the other further back, ranging between six-tenths (1.5 centimeters)
to nine-tenths (2.3 centimeters) of an inch above the tile.
Space shuttles have landed safely
many times with gap-filler protrusions, and the same may hold true for
Discovery, shuttle officials have said.
But mission managers said Sunday
that added analysis was warranted
since the two seen during the current STS-114 flight stick out further out than
those found after past orbiter landings.
Analysts are expected to present
data to the MMT today regarding the potential increased local heating effects
that could stem from simply leaving the gap-fillers in place during reentry,
information which will likely factor into the management team's decision, shuttle
officials said.
"No decision has been made yet as to
whether, in fact, we're going to down and do this," said Phil Engelauf, STS-114 mission operations representative, said
of the potential repair.
A just-in-case plan
Begley said that, should the
gap-fillers need to be addressed, Robinson would be placed at the end of the
robotic arm attached to the International Space Station (ISS), where Discovery
is currently docked.
Whether STS-114 pilot James Kelly or
mission specialist Wendy Lawrence would helm the ISS arm - both have done so
during the current docked operations - is not yet decided, added Mark Ferring, lead ISS flight director for the STS-114 flight.
Armed with forceps, scissors, a
modified hacksaw, and his own two hands, Robinson would then be positioned
sideways under the orbiter, spacewalk officials said.
Current plans would call for
Robinson to simply pull on the gap-fillers with his spacesuit-clad fingers to
remove them or, failing that, he could use forceps to hold protrusions while
shearing it off with the hacksaw, Begley explained.
"It's cutting and pulling," Begley
said. "It's very simple skills and very simple tools."
The scissors are currently at the
bottom of the preferred tool list, since they may not cut as much of the
material off and could bring Robinson's gloved hands closer to the shuttle
tiles, she added.
Robinson's spacewalking partner,
astronaut Soichi Noguchi of the Japanese Aerospace
Exploration Agency (JAXA), would not accompany his counterpart beneath the
shuttle's belly, Begley said.
"It only takes on crewmember to do
it and we'd want to avoid too many tools or other items...at the end of arm to
protect the vehicle as much as possible," she added.
Spacewalking tools typically left
free-floating during an EVA, such as tethers and other equipment, would be tied
close behind Robinson to prevent damaging Discovery's ceramic tile heat shield,
Begley said.
While it could take at least 90
minutes to pre-position the ISS arm, then another 45 minutes to transport
Robinson to his first gap-filler worksite, the actual repair should go
relatively quickly, Begley added. Moving from one gap-filler site to the other
could take about 10 minutes, she said.
Robinson and Noguchi would have to
give up at least one task on their third EVA - most likely the installation of
a camera and lighting package - to wedge in the gap-filler fix, though the
astronauts have already racked up enough extra time in two spacewalks
for the planned installation of a spare parts platform and the added retrieval
of a broken rotary motor along the station's exterior, Begley said.
NASA officials stressed that the
plans laid out by Begley are still preliminary since the MMT has not made
definitive decision on what, if any, action may be required for the
gap-fillers.
A press briefing on the results of
today's MMT meeting is slated to begin at 6:00 p.m. EDT (2000 GMT).
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