Shannon leaning toward spacewalk repair of blanket
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: June 10, 2007
Concern about possible re-entry heat damage to the underlying structure of the shuttle Atlantis' left-side maneuvering rocket pod under a pulled-up insulation blanket may prompt a simple spacewalk repair job, the chairman of NASA's Mission Management Team said today.
John Shannon told reporters that engineers studying the protruding triangular 4-inch by 6-inch blanket are concerned about the possible effects of re-entry heating on the graphite epoxy honeycomb structure of the shuttle's left Orbital Maneuvering System pod.
Shuttles have safely returned to Earth on several occasions with broken or lost tiles and lost blankets on the OMS pods. But in some cases, the underlying structure was damaged and required repairs.
"We have actually damaged that on several of those flights where you had some heat effects," Shannon said. "When we talked to the engineering guys and the structural team, they were a little bit uncomfortable today. And the reason they were uncomfortable was because if you get down to that honeycomb, that structural area, you're losing some margin, you're not exactly in the flight parameters you expect to go fly."
He said it was difficult to accurately predict what sort of damage might occur because engineers cannot tell how much underlying insulation might have pulled away with the blanket.
"Because we do not want to damage flight hardware, we sent off a (team of engineers) to work with the EVA, the spacewalk team, to go assess some options. The simplest is we would just tuck that blanket back down and fill that cavity back up. And they're talking about different ways to maybe secure it.
"We did not judge what the right answer was, we're going to let that spacewalk team go off and assess that and they'll come back to me tomorrow and lay out options, pros and cons, and then we'll decide A) if we want to do anything with this blanket and then if we do want to do something, what is the right course of action."
"You have the heating of the vehicle in this area that goes up and is significant for 15- to 20-minute period of time but you really don't have any aerodynamic loads on it at that time, it's very, very low dynamic pressure on that blanket area," Shannon said. "So after you get through the high heating area, then you start to pick up aerodynamic loads.
"What does that mean to you? Well, what it means is whatever condition you start re-entry in with that cavity, or that blanket, it's going to pretty much stay in that configuration throughout the high-heating time frame. Then it might change, it might pull up more, whatever, in a time when you don't really care very much."
Shannon said he was not leaning one way or the other toward ordering a repair, saying "tomorrow I'll have a better idea of what the different options are."
But a few minutes later he said, "I think after seeing the effect on the graphite epoxy honeycomb on some (past flights) I'm leaning may be a little bit toward doing it, but we have to hear what the options are."
Because engineers don't know exactly what sort of heat damage to expect, "I would just like to kind of avoid that whole scenario altogether and tuck that blanket back down. And I'm expecting the team to come in and give me some ideas of how to do that and then we'll see where it fits in the timeline. If we can accommodate it, I think that's probably what we'll do."
The Atlantis astronauts plan spacewalks Monday, Wednesday and Friday to activate and configure a new solar array and to carry out a variety of other tasks. If a repair job is added, it likely would occur during the third spacewalk, after the high-priority work to complete the activation of the new solar arrays.