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Small piece of foam falls from fuel tank BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: July 3, 2006 Engineers are readying the shuttle Discovery for a third launch try Tuesday amid hurried work to assess the potential impact of missing foam insulation on the ship's external tank that broke off Sunday after a launch scrub. The triangular piece of foam that broke away from a bracket supporting a 17-inch-wide liquid oxygen feed line was found on the surface of Discovery's mobile launch platform during a standard post-fueling inspection. The piece weighed just .0057 pounds - .091 ounces, or about the weight of a penny - and was roughly half of the mass that would result in a 1-in-100 chance of catastrophic damage to the shuttle's heat shield. Photos of the foam are available here. "The obvious question is, well gee, if this were to happen in flight and this piece of foam were to come off, would that have been in issue?" said John Shannon, chairman of NASA's Mission Management Team. "And the answer is no, absolutely, it would not have been an issue. It was less than half the size that we think can cause damage to the orbiter. So although it is in an area where we don't like to have foam come off, it would not have caused any damage to the orbiter itself." But engineers want to make sure the remaining foam on the bracket in question will stay in place; that the loss won't lead to dangerous ice buildups on the bracket prior to launch; and that enough insulation remains in place to prevent the underlying structure from heating up too much during Discovery's climb to space.
The forecast for Tuesday calls for a 60 percent chance of acceptable weather with the major concerns being rain showers in the area and heavy cloud cover. The forecast for Wednesday is 60 percent no-go. "Tomorrow's a good day, the next day's a good day, I cannot differentiate between 40 percent go or no go or 60 percent go or no go," Shannon said of Florida's mercurial summertime weather. "Weather really doesn't play into this discussion at all. It's are we good from a technical standpoint to go fly or are we not? And if we're not, we'll go get the technical data." NASA has spent more than three years following the Feb. 1, 2003, Columbia disaster trying to minimize foam shedding from the shuttle's huge external tank. The bipod foam responsible for Columbia's destruction has been removed, as have long foam wind deflectors that were the source of a chunk of foam that broke away during Discovery's launch last year. NASA Administrator Mike Griffin cleared Discovery for flight over the objections of his chief engineer and safety manager, who raised questions about yet another area of insulation on the tank that is officially classified as an unacceptable risk. That foam, which covers 34 brackets on the tank that support two pressurization lines and a cable tray, is not an issue in today's discussion. The bracket in question is one of several that support the much larger 17-inch liquid oxygen feedline that carries oxygen from the top of the external tank to the shuttle's engine compartment. NASA attempted to launch Discovery Saturday and Sunday, only to be blocked both times by afternoon showers and associated electrical activity. The team was told to stand down after Sunday's attempt in order to top off on-board supplies of liquid hydrogen before making another attempt Tuesday. During inspections of the tank after Sunday's fueling, engineers first noticed a crack in the foam on the uppermost oxygen feedline bracket. Later, after a rotating service structure was moved back into place around the orbiter, engineers discovered the small piece of foam that broke away from the bracket. Roughly the size and shape of a corner of a piece of toast, it's the largest such foam debris ever found on the launch pad. "There are several brackets down the side that hold (the feedline) structurally onto the tank itself," Shannon said. "When the tank, when we fill it up, it shrinks and when you de-tank, it expands and what you need is an articulating joint here at the bracket that can move back and forth as the tank moves relative to the LOX feedline. "What we think happened yesterday, when we had all that rain that scrubbed the launch, we had some condensation running down the LOX feedline. It froze, and we got some ice build up in that articulating joint. When the tank was emptied and it started to warm up, it started to expand and we think some of that ice stayed in that joint and it crushed a little bit of that foam. "What the inspection team reported was a small crack in that joint," Shannon said. "That was the initial report that we got. ... When we moved the rotating service structure around, and I think this was just coincidence, any residual ice in there that was creating the pinch point that caused that crack in the first place melted and that small piece came out of that cracked area and landed down on the launch platform." The Mission Management Team kicked off an intense, three-pronged attack: 1. Find out what impact, if any, the loss of insulation from the bracket means in terms of ascent heating to the underlying structure. "The team is very confident there's not going to be an issue with the foam that was lost in that area with any aerothermal heating because that structure has got a lot of margin to it," Shannon said. But an analysis is underway to prove that. 2. Determine whether the loss of insulation will result in ice formation on the bracket that could break off during launch and damage Discovery's heat shield. "We're still doing analysis on that," Shannon said. "What I think will probably happen is we will not come to a very conclusive answer tonight but I am very comforted by the fact that we have an ice team that goes out there and they have excellent views of this area. ... If ice were to form that was a danger to the orbiter, the ice team would see it and we would stop the count." 3. Determine whether any other areas of insulation on the bracket are damaged. The upper section of the bracket cannot be easily seen without first mounting a platform on the launch pad gantry to give engineers access to the area. If an inspection is required, launch would be delayed at least one day. "What we decided to do today in the MMT was to allow the team to have some time to go answer these questions, do the aerothermal analysis, go review the ice formation ... and third was to go think of ways that we could inspect the rest of that foam and make sure it's all intact," Shannon said. "And the team is looking at different options." Engineers have never attempted a foam repair of this nature at the launch pad. But at this point, the debate seems to be more focused on whether to carry out a detailed inspection or whether engineers can develop a sound rationale to fly as is. "We believe that we're getting much more comfortable with the ability to potentially fly," said John Chapman, manager of the external tank project for NASA. "But the team is still looking at that. We want to make sure we understand all the considerations that could cause this foam to be lost." Shannon said the MMT is not falling prey to "go fever" and that he has no preconceived notions about how to proceed. "If we decide we're a little bit uncomfortable with this, or we haven't completed our analysis or we need some more data, there is the potential that tonight I'll decide ... We want to go out there tomorrow with a platform and just make absolutely, 100 percent sure there are no other problems with that strut. I have no preconceived notion for how that discussion is going to go."
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VIDEO:
JOHN SHANNON EXPLAINS THE FOAM SITUATION 
