NASA: Shuttle Discovery may need another space repair
Although astronaut Steven Robinson removed two gap fillers from Discovery's underside, a ruffled thermal blanket below the shuttle commander's window worried mission managers at NASA.
Engineers informed the shuttle crew on Wednesday there was a chance that a fourth spacewalk might be needed Friday to deal with the torn thermal blanket.
They said the blanket does not pose a danger to overheating. However, engineers are performing tests overnight to determine the likelihood of the blanket coming off during the shuttle's descent and becoming a source of debris.
The 50-centimeter section of the blanket could rip away during re-entry, whip backward and slam into the shuttle, perhaps causing grave damage, NASA said. Engineers expect to know by Thursday evening whether the danger is real and whether any blanket trimming is required.
In a Wednesday afternoon briefing, NASA's deputy shuttle program manager Wayne Hale said a team of aerodynamic engineers are working around the clock to perform several tests with three sample blankets.
The team will try to replicate the damage and simulate the shuttle's descent in a wind tunnel to learn how the insulating material might react. The aerodynamics team is seeking to understand when, if at all, the blanket could tear away and what size piece or pieces could come off.
Meanwhile, the mission control team is developing a plan for a potential additional spacewalk repair for the thermal blanket, Hale said.
NASA hailed shuttle crew's third spacewalk as "an excursion in the history books." The spacewalk featured the first-ever on-orbit repair of a shuttle's heat shield and attachment of a stowage platform onto the International Space Station.
The heat shield repair efforts occurred quickly and just as planned on the shuttle Discovery's underbelly. Robinson removed gap fillers that were protruding from two areas between heat-shielding tiles on Discovery. He gently tugged the gap fillers until they came out.
After he removed the second protrusion, Robinson declared, "it looks like this big patient is cured."
Robinson also took pictures of Discovery's heat shield before leaving the area and returning to the payload bay. Meanwhile, fellow spacewalker Soichi Noguchi provided communications and visual support to Robinson and flight controllers.
The first task of the spacewalk was the installation of the External Stowage Platform-2 by Robinson and Noguchi. They were assisted by the International Space Station's robotic arm. Then, Noguchi installed a materials exposure experiment on the Station's exterior.
In other activities, Mission Control asked the crew to use the Orbiter Boom Sensor System to inspect insulation blankets under the commander's window on Discovery. Cargo stowage continued on the Space Station, NASA said.
Source: Xinhua
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