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STORY WRITTEN FOR & USED WITH PERMISSIONPosted: February 6, 2005KENNEDY SPACE CENTER, Fla. - With the first post-Columbia shuttle flight just three-and-a-half months away, astronauts and engineers are engaged in a sometimes heated, down-to-the-wire debate over which tile and wing leading edge repair techniques to test in orbit. Astronauts are against the tile-repairing concept of injecting a goo-like substance into the damage area. Photo: NASAThe astronaut office at the Johnson Space Center in Houston now opposes one tile repair technique once considered a front runner, arguing it's too inconsistent, and thus unreliable, to warrant tests aboard the shuttle Discovery during mission STS-114 in May. "It is a really challenging problem," chief astronaut Kent Rominger said in a telephone interview Friday. "But we're at the point, from our insight with looking at where it is and where we are, we do think we're better off without it on STS-114." Many engineers disagree, saying tests in the airless, weightless environment of space are precisely what are needed to work the bugs out and learn whether the technique can ever be formally certified for use. "For many of the repair techniques, not all but many of them, one of the key elements is to do it in vacuum and zero G and let it cure, or set up, and then bring it back and put it in our re-entry simulator, the arcjet," said Wayne Hale, deputy manager of the space shuttle program. "To most of us, it makes sense that that is the last step in certification. Do it on orbit, bring it back and put it in the highest fidelity re-entry simulator." The procedure requires a spacewalking astronaut, wearing a large backpack with a sort of high-tech caulk gun, to fill or patch areas of damaged tile with a thick heat-resistant material known as STA-54 that would then cure in place, providing a barrier against re-entry heat. Recent tests, however, show air bubbles can form in the material as it is mixed in the backpack, possibly reducing its effectiveness as a barrier against re-entry heating. Other questions involve the crew's ability to apply the material properly and its ability to adhere to the underlying surface. "The office has taken a position that the systems are really just not developed along enough to do an effective demonstration," said Andrew Thomas, a member of Discovery's crew. In the midst of that debate, a new tile repair technique, developed by a small group of engineers working on their own, has emerged in recent weeks that could provide a way out of the tile repair quandary if additional testing and analyses confirm initial results. The so-called "overlay" technique calls for spacewalking astronauts to cover damaged tiles with thin, flexible sheets of heat-resistant carbon silicon-carbide that would be mounted atop a gasket and attached with fasteners similar to drywall bolts that would be screwed into surrounding tile. The procedure, which appears relatively easy to carry out in weightlessness, is essentially a mechanical fix and as such, not susceptible to the sort of problems seen in STA-54 testing. But the overlay technique has not been subjected to the same level of scrutiny as STA-54 and the jury is still out on whether it might ultimately make its way on board Discovery. "It would have some pluses and minuses," Thomas said in an interview. "You don't have the problem of the material flowing, the adhesion problem, which is really a very tricky problem. But you've got other issues, namely you've got a material edge which you wouldn't want air flow to get under so you've got to somehow button that down. "The fasteners I've seen are actually pretty slick, though," he said. "They're low profile, very smooth and flush mounted, they're made of RCC-type materials. And they work, by all accounts, they seem to work very well. But there's a lot more development that's needed on that, too. It's not ready for prime time." Not yet, maybe. But supporters believe the technique has great promise and Rominger said he supports in-flight tests by Discovery's crew. "Absolutely. As a matter of fact, that looks really encouraging to me," he said. The shuttle Columbia, of course, was not brought down by tile damage. It was the victim of a hole in a reinforced carbon carbon wing leading edge panel that was caused by the impact of foam debris falling from the ship's external fuel tank during launch. Shuttle managers initially downplayed any realistic chance of developing techniques for repairing the shuttle's RCC panels in time for return to flight, citing the technical challenge of coming up with fixes capable of withstanding 3,000 degrees during re-entry. Instead, the approach was to upgrade the external fuel tank's insulation to eliminate the possibility of large debris strikes. The 1.7-pound chunk of foam that triggered Columbia's destruction came from an area known as a "bipod ramp," which insulated one of the fittings used to attach the shuttle's nose to the tank. Acting on a recommendation from the Columbia Accident Investigation Board, NASA has eliminate the bipod foam and implemented other changes to ensure no debris larger than about 0.03 pounds - half an ounce - can come off the tank during launch. But engineers never stopped working on RCC repair options and recent testing shows those techniques may be more mature than any of the proposed procedures needed to repair the tiles on the belly of the shuttle. "I was of the opinion early on that it was more important for us to demonstrate the RCC repair because that was the immediate cause of the Columbia accident," Hale said. "Several months ago, folks in the technical community were of the opinion that tile repair was more mature, RCC repair was less mature, we ought to do tile repair (aboard Discovery). "Now it appears that RCC repair may be more mature and tile repair less. So we may be doing the first flight demonstration test on RCC repair rather than tile repair because it's readier." Rominger agreed, saying "I've been really impressed with the kind of progress we have made in RCC repair." "For some reason, from the start, we really tied ourselves to tile repair when in fact that's not what killed us on Columbia," Rominger said in an interview. "On every shuttle flight we've flown, we've damaged the tile and if anything, we've proven how robust it is." Luck, however, played a role in previous tile damage - no critical systems were affected before Columbia's flight - and Rominger said NASA clearly needs to develop a reliable tile repair procedure. "But I am really excited seeing all the progress we've made in RCC repair," he said. "I'm cautiously optimistic that with the number of different repairs we have out there (that), maybe not on 114 but not too far down the road, we will have pretty decent RCC repair capability." Hale said Friday that meetings are planned in the next week or so to discuss the technical feasibility of the proposed RCC and tile repair procedures and to select those that will be tested by the Discovery astronauts in May. "The question we're about to come to is, what is ready to fly in May?" Hale explained. "We have got to decide what we're going to fly and what we're going to train the crew for." Whatever is decided, Rominger said the astronaut office will accept the outcome. "In today's environment, they go around and ask everybody at the table, what do you think?" he said. "All along we've said, here's our input, take it for what it's worth, and when you come back with a decision we will salute sharply and do our best with whatever that is." Ares 1-X PatchThe official embroidered patch for the Ares 1-X rocket test flight, is available for purchase.Apollo CollageThis beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.Expedition 21The official embroidered patch for the International Space Station Expedition 21 crew is now available from our stores.Hubble PatchThe official embroidered patch for mission STS-125, the space shuttle's last planned service call to the Hubble Space Telescope, is available for purchase. | | | | 2014 Spaceflight Now Inc.Entry and Landing Timeline COMPILED BY WILLIAM HARWOODUpdated: Aug. 3, 2005Changes and additions:- Dec. 19: Posting initial version of timeline- April 5: Posting updated version- April 20: Updating to reflect 5/22 launch target- May 10: Updated version to reflect July launch date- June 17: Updating TIG/landing time; adding backup TIG/landing times for KSC and Edwards- July 7: Updating landing times- July 21: Updating with 7/26 launch target- Aug. 3: Updating landing date, time; adding projected entry dataDownload a of the timeline. Ares 1-X PatchThe official embroidered patch for the Ares 1-X rocket test flight, is available for purchase.Apollo CollageThis beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.Expedition 21The official embroidered patch for the International Space Station Expedition 21 crew is now available from our stores.Hubble PatchThe official embroidered patch for mission STS-125, the space shuttle's last planned service call to the Hubble Space Telescope, is available for purchase. | | | | 2014 Spaceflight Now Inc.First spacewalk of Discovery mission meets all objectives BY WILLIAM HARWOOD