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Astronauts await tile repair decision BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: August 16, 2007 The Endeavour astronauts are awake and working through a revised flight plan today, awaiting word from NASA's Mission Management Team on whether the space shuttle's gouged heat shield can stand up to the rigors of re-entry as is or whether an unprecedented tile repair spacewalk will be needed Saturday. During a morning "big picture" update for commander Scott Kelly, astronaut Chris Ferguson in mission control said a decision was expected by noon or shortly thereafter. "Understand the decision might be made today at noon and we won't actually pull any of the (tile repair) hardware out until then. Is that still something the guys are anticipating?" Kelly asked. "Yeah, Scott, we have every reason to believe that a decision is going to be made by noon and that's why the flight plan for today was put together the way that it was," Ferguson replied. "The idea is to not have you drag anything out unless you need to have it out so you don't have to put it away. But you know, I mean the MMT working the way that sometimes these things work, it may get delayed. And if it does, we're going to have to stick to the flight plan and pull some of the equipment out. But, hopefully, by lunch we will have some words for you." "OK. If that was to happen and they were to call the repair off, we were discussing the possibility of doing EVA-4 tomorrow," Scott said, referring to the crew's originally planned fourth and final station assembly spacewalk. "Is that something you guys are looking at?" "Yeah Scott, I think we're going to kind of stick to the plan we have right now and that is, still plan for the EVA on flight day 11 (Saturday)," Ferguson said. "What that would mean, however, if they do call it off we'd make the latter part of the day after lunch off-duty for everyone." The astronauts were awakened, appropriately enough, with a recording of "Times Like These" by the Foo Fighters. Flight controllers are preparing revised timelines to cover both possibilities for Saturday's spacewalk - tile repair activity by Rick Mastracchio and Dave Williams or the normal space station EVA by Williams and astronaut Clay Anderson. Either way, the astronauts were asked today to expedite close-up photos of the spacesuit gloves used in a station assembly EVA Wednesday. Mastracchio had to end his participation in the excursion early when he noted a small tear in the Vectran outer layer of the material on his left thumb. The additional photos are required before Saturday's spacewalk, whatever its content might be, to confirm some sort of generic defect is not present. At 8:06 a.m. today, teacher-turned-astronaut Barbara Morgan and Al Drew will participate in the second educational event of Endeavour's mission, chatting with students and officials at the Challenger Center in Alexandria, Va. The Challenger Centers for Space Science Education were created in the wake of the 1986 shuttle disaster by the crew's families. The founding chairman is June Scobee Rogers, widow of Challenger commander Dick Scobee, who will host today's event. Along with the educational event, Morgan and other crew members also will participate in round-robin media interviews starting at 10:16 a.m. If a heat shield repair spacewalk is ordered, Mastracchio and Williams will begin breaking out the required tools and equipment this afternoon. If the repair is deemed unnecessary, the astronauts will take a few additional hours off to relax. In a morning message uplinked to the crew, flight controllers said "the short story on damage assessment is that the Arc Jet tests are thus-far supporting the CFD analysis and indicate that a repair may not be necessary. An additional arc jet test was conducted last night and these results along with the peer review of the CFD analysis and QA of the model will be the final determining factor. "We have tried to leave as much flexibility in todayšs Flight Plan as possible by deferring the actual retrieval of the repair tools until after lunch. The idea, of course, is to avoid gathering items we will only have to re-stow if the repair is not required. Wešre hoping for a lunch-time decision, but in the event it is delayed we will have to begin opening bags." An updated flight plan will be posted here after mission managers decide on a course of action. In the meantime, here is the flight plan for today as it now stands (in EDT and mission elapsed time; NOTE: NASA rounds all times down to the nearest minute. This page rounds up or down as required): EDT........DD...HH...MM...EVENT 05:37 AM...07...11...00...STS/ISS crew wakeup 08:06 AM...07...13...30...Educational event with Barbara Morgan 08:17 AM...07...13...40...EVA-4 training and review 10:16 AM...07...15...40...News media interviews with Morgan 10:37 AM...07...16...00...Logistics transfer operations 11:17 AM...07...16...40...EVA-4 tagup with mission control 12:02 PM...07...17...25...Crew meals 01:02 PM...07...18...25...Crew off-duty time 03:37 PM...07...21...00...EVA tools gathered and unpacked 05:37 PM...07...23...00...STA-54 and emittance wash preparation for EVA-4 05:52 PM...07...23...15...Logistics transfer tagup 08:37 PM...08...02...00...ISS crew sleep begins 09:07 PM...08...02...30...STS crew sleep begins At the Johnson Space Center, engineers are wrapping up analyses of the heat shield gouge and comparing sophisticated computer modeling results with final test runs in a high-temperature furnace to make sure the computer predictions match up with the actual re-entry environment. Computational fluid dynamics calculations indicate the aluminum skin below the gouge in two tiles on the belly of the shuttle will not exceed NASA's conservative 350-degree design limit. The computer calculations indicated the skin temperature would only rise some 40 degrees above normal and stay below the limit. A mockup of the damage using tiles deliberately carved out to mimic the damage on Endeavour were put in the arc jet facility and subjected to the sort of 2,200-degree wind the shuttle will experience during peak heating. Again, the temperature of the aluminum skin under the tiles did not climb above 350 degrees. The final tests carried out overnight involved a tile mockup with more idealized damage, a carved pit with the sort of straight lines and angles used in the computational fluid dynamics model. The idea is to make sure the computer models are accurate and do not include any incorrect assumptions. As an additional safety check, the analyses is being independently peer reviewed. "The primary point of debate (Wednesday) was did we need to run the simplified model in the arc jet facility?" said John Shannon, chairman of the Mission Management Team. "Because a lot of folks thought that we had two fairly independent analyses, one was the thermal analysis done on computer, one is the arc jet that said you don't have a problem here. But just to tie the two together and make sure we didn't make some significant error in either of those, we're going to run this simplified model in the arc jet. That was the primary point of discussion. People thought we had enough data, some people wanted to go get some more data. So we're going to go get some more data." Two heat-shield tiles on the shuttle's belly were damaged when a chunk of foam debris, possibly including ice, slammed into the orbiter 58 seconds after launch last Wednesday. The impact gouged out an irregular pit in the tile measuring roughly two inches by three inches across and nearly penetrating the full 1.12-inch thickness of the tile. A small, 1-inch by 0.2-inch gash at the bottom of the pit exposes an underlying support pad just above the shuttle's aluminum skin. The shuttle Columbia was destroyed in 2003 when it re-entered the atmosphere with a gaping 4- to 6-inch hole in the leading edge of its left wing. NASA managers, and even commander Scott Kelly, say they do not view Endeavour's gouge as a Columbia-class problem. Shannon said the issue is whether re-entry heating might cause damage to the shuttle's aluminum skin in the immediate area that would require time-consuming post-landing repairs. But Shannon made it clear he viewed the risk of a spacewalk repair as significant and that such a repair could only be justified if it was necessary to prevent serious damage during re-entry. And based on the testing and analysis through Wednesday, that did not appear to be the case. But, as Shannon cautioned, the analyses is not complete and any major surprise or disagreement between the computer models and the arc jet facility could change that assessment.
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VIDEO:
PREVIEW OF SPACEWALK NO. 3 