NASA assesses threat posed by cockpit window blanket
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 2, 2005
Amid planning for an unprecedented shuttle heat-shield repair spacewalk Wednesday, engineers also are assessing the potential threat posed by a damaged insulation blanket just below commander Eileen Collins' left cockpit window. While engineers say the blanket poses no threat of heat damage during entry, there's a chance a small portion of the blanket could rip away in the lower, denser atmosphere and hit the shuttle's aft section.
"The folks who have been looking at that, of course, have been heavily involved in many of the aspects of the gap filler discussion (see below), the aerodynamics and so forth. ... They're now looking at where that blanket might go if it actually comes off during entry."
The analysis is expected to be complete by Thursday.
"Right now, we know that in terms of the local area, it's OK," Hale said of the damaged blanket. "This is just a question of could it fly back and hit something on the after part of the vehicle? And, in fact, the biggest work going on, I think, is to determine whether or not it's even possible the blanket could come off.
"It appears to be well adhered in terms of the underlying RTV glue," he said. "And the stitching holding it down to the edges of that looks like it's in good shape."
Hale said the blanket, which measures 20.4 inches long and 3.8 inches wide, appears to have been hit by something earlier in the mission. Impact damage of some sort is the presumed culprit, but that is merely an assumption at this point. Unlike the gap filler problem, the blanket poses a threat when the shuttle is much closer to Earth, and flying much slower. In relative terms, of course.
"This would not be a concern if it came off at high Mach number, above Mach 6," Hale said, referring to a velocity six times greater than that of sound. "You know, once you get to Mach 6 with the shuttle, you're just kind of putzing around. At lower Mach numbers, where the air is thicker, then there is some transport mechanism that folks are going to go off and look at.
"They're concerned about a physical impact," he said. "The heating concerns rapidly go away later in the trajectory. So, this would not be a high-heating, high-Mach-number kind of concern. This would be a low Mach number, impact-if-any kind of concern."
He said engineers believe the largest piece that could rip away would weigh just 0.05 pounds or so - eight tenths of an ounce.
This issue does not appear to be serious. But given the way Discovery's flight has been proceeding, readers are urged to stay tuned.
Discovery safely touched down at 8:11 a.m. EDT (1211 GMT) Tuesday morning at Edwards Air Force Base in California.
Weather worries off the coast of Florida thwarted both landing opportunities this morning at Kennedy Space Center, forcing a detour to the backup landing site.
See the Status Center for full play-by-play coverage.
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