"We have cleared Discovery to re-enter," said Wayne Hale, chairman of the Mission Management Team (MMT), during a news conference at NASA's Johnson Space Center, Houston.
The MMT determined the orbiter's heat shield and other systems are in good shape. They also decided a spacewalk is unnecessary to repair damage to a thermal blanket on Discovery's outer skin.
Earlier this week, Discovery (STS-114) mission managers determined two components of the Shuttle's Thermal Protection System, tile and Reinforced Carbon-Carbon, were fit for re-entry and landing. Today, the MMT cleared the final element: thermal blankets. One blanket is slightly torn and billowing in orbit.
The MMT considered the results of overnight testing at NASA's Ames Research Center, Moffett Field, Calif. Engineers ran samples of torn thermal blankets through wind tunnels at velocities many times faster than the speed of sound. Tests showed it was highly unlikely the blanket would tear off or strike the orbiter. Other analyses showed the blankets would still protect Discovery from re-entry heat.
Based on the analysis of the blankets and considering the risks of a fourth spacewalk, mission managers decided the torn blanket did not need repair. "We've assessed this risk to the very best of our knowledge, and we believe the risk is small," Hale said.
New imaging capabilities developed after the Space Shuttle Columbia accident allowed mission managers to see and analyze the torn thermal blanket. Data from the images were used to re-create blanket samples for the wind tunnel tests. "I think it's remarkable we have capability to look at these small things in flight," Hale said.
Discovery is set to land Monday, Aug. 8 at NASA's Kennedy Space Center, Fla. The first opportunity for Commander Eileen Collins to land the Space Shuttle is at 4:46 a.m. EDT.
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