NASA Details Plans for Potential Fix to Discovery's Heat Shield

HOUSTON - As shuttle managers debatewhether an untried repair is needed to pry two space-filling strips from theunderside of the Discovery orbiter, spacewalk planners have chosen whichastronaut would perform the potential task, the mission's lead spacewalkofficer 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 missionmanagers decide it is necessary later today, said Cindy Begley, the flight'slead 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-fillersjutting out from between the heat tiles lining the shuttle's forward section orleave them as is.

"We don't currently have directionsto do [the repair] but as always we try to get all our ducks in a row ahead oftime," Begley said. "Something we've never been done before is put a crewmemberunderneath the vehicle."

Shuttle tile gap-fillers are smallstrips of ceramic fiber cloth glued between the orbiter's heat-resistant tilesto fill excess space. Orbitalphotographs and a subsequent focusedinspection detected two gap-fillers jutting out; one sticking 1.1 inches(2.7 centimeters) out of a region just behind Discovery's nose landing geardoors 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 safelymany times with gap-filler protrusions, and the same may hold true forDiscovery, shuttle officials have said.

But mission managers said Sundaythat added analysis was warrantedsince the two seen during the current STS-114 flight stick out further out thanthose found after past orbiter landings.

Analysts are expected to presentdata to the MMT today regarding the potential increased local heating effectsthat could stem from simply leaving the gap-fillers in place during reentry,information which will likely factor into the management team's decision, shuttleofficials said.

"No decision has been made yet as towhether, in fact, we're going to down and do this," said Phil Engelauf, STS-114 mission operations representative, saidof the potential repair.

A just-in-case plan

Begley said that, should thegap-fillers need to be addressed, Robinson would be placed at the end of therobotic arm attached to the International Space Station (ISS), where Discoveryis currently docked.

Whether STS-114 pilot James Kelly ormission specialist Wendy Lawrence would helm the ISS arm - both have done soduring the current docked operations - is not yet decided, added Mark Ferring, lead ISS flight director for the STS-114 flight.

Armed with forceps, scissors, amodified hacksaw, and his own two hands, Robinson would then be positionedsideways under the orbiter, spacewalk officials said.

Current plans would call forRobinson to simply pull on the gap-fillers with his spacesuit-clad fingers toremove them or, failing that, he could use forceps to hold protrusions whileshearing it off with the hacksaw, Begley explained.

"It's cutting and pulling," Begleysaid. "It's very simple skills and very simple tools."

The scissors are currently at thebottom of the preferred tool list, since they may not cut as much of thematerial off and could bring Robinson's gloved hands closer to the shuttletiles, she added.

Robinson's spacewalking partner,astronaut Soichi Noguchi of the Japanese AerospaceExploration Agency (JAXA), would not accompany his counterpart beneath theshuttle's belly, Begley said.

"It only takes on crewmember to doit and we'd want to avoid too many tools or other items...at the end of arm toprotect the vehicle as much as possible," she added.

Spacewalking tools typically leftfree-floating during an EVA, such as tethers and other equipment, would be tiedclose behind Robinson to prevent damaging Discovery's ceramic tile heat shield,Begley said.

While it could take at least 90minutes to pre-position the ISS arm, then another 45 minutes to transportRobinson to his first gap-filler worksite, the actual repair should gorelatively quickly, Begley added. Moving from one gap-filler site to the othercould take about 10 minutes, she said.

Robinson and Noguchi would have togive up at least one task on their third EVA - most likely the installation ofa camera and lighting package - to wedge in the gap-filler fix, though theastronauts have already racked up enough extra time in two spacewalksfor the planned installation of a spare parts platform and the added retrievalof a broken rotary motor along the station's exterior, Begley said.   

NASA officials stressed that theplans laid out by Begley are still preliminary since the MMT has not madedefinitive decision on what, if any, action may be required for thegap-fillers.

A press briefing on the results oftoday's MMT meeting is slated to begin at 6:00 p.m. EDT (2000 GMT).

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