Columbia Accident Investigation Board
Home Board Charter Board Members News Photos Events Contact The CAIB
Columbia Accident Investigation Board Roundtable
Tuesday, June 24, 2003

2:30 p.m.
National Transportation Safety Board
Conference Center
429 L' Enfant Plaza, SW
Washington, D.C.

MS. LAURA BROWN: Okay. Thanks for waiting again, and I think most of you know Scott Hubbard. He's been in charge of the foam testing done in San Antonio, and he's going to give us an update.

MR. SCOTT HUBBARD: Okay, good afternoon. This is part of an ongoing series of tests of impacting the foam against the wing leading edge in order to establish the connection from foam to breach. The impact on the RCC panel six, I think, gave us a plausible failure scenario, and what we're trying to do here is to see, by doing these impact tests, can we establish that we have the data, as Admiral Gehman said a little earlier, to say the words "highly probable" or "most likely." So, that is the purpose of this – of these tests.

Okay. So, let's go to the first slide. We have conducted, since we last talked to you, two fiberglass tests, one that was on June 16th and one that was on June 18th, and these were designed to answer three questions. I think I told you about this the last time we were together. But, just to refresh your memory, first of all, we wanted to understand do these panels act as a system, or are we simply looking at the interaction of the foam hitting a single panel or a single T-seal. And I have a new model here, which I'll refer to several times, that shows how the test article has been structured. This is the piece of material that we're using down at the tests in San Antonio, and it goes from panels five, six, seven, eight, nine and 10, and what we're trying to find out, first of all, is when you hit this with a piece of foam, does the entire wing-leaning edge respond, or are we looking at a localized phenomenon that created the breach, and I'll come back to this as we talk about the results.

Second thing I want to talk about is the question of where the foam hit. The visual record, the sensor record, doesn't tell us that exactly. You've heard from other board members that the interpretation of the debris evidence and some of the sensor evidence seems to indicate that the breach was in the lower part of panel eight, which is this panel here, but we don't have, as yet, any experimental evidence that establishes that the foam, in fact, could create a breach of sufficient size to create the accident. So, what we're doing is removing the impact position of the foam down closer to where the debris evidence indicates that it probably occurred. That's part of the set of fiberglass tests, and will be part of the next and final series.

Final thing is what happens as the foam impacts the wing-leading edge with different areas? Couple of you who have been to San Antonio have heard me speak of the term "Clocking Angle." I'll show you in a picture clearly what we mean by that. But, the point of the test is, does it make a difference. As this piece of debris was tumbling and spinning, whether or not it hit just with a corner, or whether it hit with an entire edge against the panel, and how is the force distributed. These are all things that we're trying to take into account to be sure that we have the most representative footprint of the foam as it hits the panel. So, those are the questions we're trying to answer by these last two tests, the system, what happens when you hit lower on the panel; and finally, what happens when you apply the force along the entire edge of a piece of foam rather than just hitting on a corner. So, let's go to the next slide.

This is our setup in San Antonio. Many of you have been there in person with our nitrogen pressurized gas gun, 30-foot barrel. We see all the lights and the high-speed cameras, and you see the wing-leading edge, panels five through 10, which has been duplicated in this model here. Lot of data-taking, several hundred channels of sensors, as well as about a dozen high-speed cameras. Now, the next slide.

The two tests were designed to answer the questions that I described. The first test, we had a target that was about three inches lower than it had been on panel six. As you know, we are using – aiming for consistently a velocity of 775 feet per second. That's a consensus on how fast this was traveling when it fell off of the bipod ramp. In this test, we were able to achieve 774. All of the tests thus far have been well within a percent or so. So, the accuracy of the gun, both in velocity and in aiming, have been quite good.

Now, we did an additional thing in here to look for the systems effects. We instrumented panel eight. If you recall, here's panel five. Here's panel six, where we're aiming, panel seven, where we've evaluated the response thus far. And we instrumented panel eight to see if this impact travels downstream very far or simply terminates within a panel or so. And I'll come back to the results of that in a minute.

Standard foam size, the 1.67 pounds that we've been using all along. The second – the next test, on June the 18th, actually is called fiberglass test three because we conducted one several weeks ago, was the same as the test on the 16th with one exception and, if you look at the picture being projected up there, you can see what I hope indicates the clocking angle, that is to say the barrel has been turned by 30 degrees. Now, what does that do for you? What it does – and I'll take off one of these RCC panels here – what it does is that, by rotating the barrel 30 degrees, rather than hitting the panel on the corner first, you actually hit the entire edge, this 11-1/2 inch edge hits on the panel, and the analysts predicted this would, in fact, transfer more force locally and would, therefore, concentrate the energy to make it more like what we believe happened during the accident. That was the purpose of the second test.

So now, let's talk a little bit about the – what actually happened during the test. The first video, then. This shows test number two, and you can see the streaks from the previous test. We left them there. You can see the panel – the foam impacting it, and see it hitting the T-seal and creating a cloud of debris. I think some of you have seen other versions from further away. I decided to show you this so that you would get a sense up close of what it looks like when the impact occurs. This loops over, and you can see that it hit on the corner first, and then if you go to the next slide, you will see how it actually impacted. And if you can see here, right there you see where it actually hit in this test versus the previous test. This is the difference. This is the three inches or so lower down. But, note that the impact footprint here is triangular. It did spill over into panels seven and even eight, to some degree.

The interesting thing about this test was that the step, that is, the difference between where the panel was and where the T-seal was, was about six-tenths of an inch, almost five-eighths, rather than less than half an inch for the first fiberglass test. So, more force was being transferred in this local region, consistent with the prediction. And you can see here, too, how much the foam got stuffed under the T-seal, creating a – as we noted some time ago, perhaps an additional failure mechanism whereby the T-seal gets shoved aside by the impact of the foam. We did see one small crack in the fiberglass, about an inch long, and as you see the results of the third test, you'll see how the force was even greater.

So, let's go to the sensor results from test two, and remember what test two was all about was firing lower down in the panel, seeing if the force down in the region where the debris indicates the breach occurred was, in fact, higher. Then – and whether or not this system of panels responded together or responded individually. And what we found was that we had very high stresses down here on panel eight. So, this whole leading edge is responding as a system. We hit here, several feet away, and stresses creating a measurement of 60,000 pounds per square inch occurred down here in panel eight, indicating that this impact had been transferred down several feet, and so the whole thing is, in fact, responding together. We can't simply say that one panel or one T-seal constitutes a test, and this is important later on as I describe the – what we're going to do next.

The face sheet motion, that is to say how much this went in and out, how much this particular area here called a face sheet went in and out, is a little over two inches compared to an inch and a half for the test on panel six. So, that showed us that there was greater local force in the bottom part of this panel, and the sensors all showed – also showed higher stress, as well. So, we learned quite a bit in doing that test. Going on to test number three, it's the same setup but, again, we rotated the barrel so that we could place this entire edge here of 11-1/2 inches flat against the panel. The prediction was this would actually result in more local stress, although maybe lower overall stress.

So, let's look at two videos there. The first one shows, again, a close-up impact of the foam on the face sheet, and you see now the entire face hits it. It breaks up. If you were to look at it from further back, you would see the entire piece of debris disintegrating. And the key thing that you'll note here, and that you'll see later on as well, is that the footprint is different. It is a more square type footprint as opposed to the triangular shaped footprint, which you might expect, given that you impact on an edge here rather than on a corner. But, it tends to be important in our thinking about how this breach may have occurred, how you were able to put so much force in an area in panel eight and actually create the hole that most of us believe is there, or knock a T-seal aside.

Let's go to the second video from test number three, and what you're going to see here is the inside. This is one of our six interior cameras, and I think you're going to get a sense of the violence of this force – of this impact – as it deflects the entire panel. And you're going to see some brightening. You see the foam coming through, and you'll see little flashes of light, and that's actually the panel being spread far enough apart to let daylight in, and then it closes up again. This was not predicted in advance, but it shows you how much the interaction between the panels and the T-seals and all – the whole system is going on.

Okay, let's go to the results from this test. Here's a couple of visual results. We now have, as I said, a footprint. If you see the streaks down here, it is a squarish area. I think we're beginning to close in on the kind of impact that probably occurred that created the breach that led to the destruction of the Orbiter. The T-seal is pushed aside. There was a lot of foam in there. But, an unanticipated result was that four large cracks appeared in the fiberglass. And fiberglass, if you remember from the previous briefings, is something like two times or more tougher in certain measurements than the reinforced carbon panels on the actual Orbiter.

If you go to the next slide, you'll see the largest single crack, which was over eight inches long. It is this rather ugly looking thing right here. So, the next slide shows the summary of the sensor results from this test. We saw four cracks that had not been previously observed. Since this panel, panel six now, had been hit twice before, one can naturally raise questions about – of whether or not this is a cumulative effect or not. In looking back at the evaluations that were done, there was no crack except for the one right after the second test. Visible, certainly nothing of the dimensions of what we see here. So, the sense of the test group is that these four cracks were created as a result of this test, indicating that a lot of force was transferred.

The face sheet motion, that is to say how much this got moved in and out, and you saw form the interior camera how violent that was. That total excursion, that total distance, was more than three inches, much greater than the previous tests. And finally, we measured up to 50 percent more stress in panel six, as well. So, the conclusion, then, is that this angle of impact does make a difference, and that it transfers far more force, as predicted, to the impacted area.

Overall then, going to the next slide, where are we? Well, by measuring panels six, seven and eight, we believe now that we have established that this leading edge system actually acts as a system, and since our models have been pretty good on predicting stress but not good on predicting breakage, the best way to simulate what happened during the accident is to make the final test on the reinforced carbon as close as possible to what we believe happened. That means you've got to test at least three panels in a row. In order to do that, it means that we're going to shoot at panel eight, not panel nine as we thought a few weeks ago. This is what – a major thing we learned from the test, so that we've got two panels downstream from it so that we simulate this system interaction.

The debris evidence, as you heard several of the board members talk about, indicates that the lower part of panel eight was probably the likely site of the breach. The forces and the footprint that seem to most closely correspond to creating that sort of breach, were the conditions we used in fiberglass test three. That was the point of doing the fiberglass tests, not that fiberglass is exactly like RCC in its detail properties, but that by comparing different conditions, we can establish, hone in on, box in the kind of conditions that would be, in our thinking, the kind that would create of some substantial size in the bottom part of panel eight. Therefore, the final RCC test that we're going to do should be in the lower part of panel eight, the same setup that we used in the third fiberglass test.

So, final slide, "What are our next steps?" We're developing a test plan together with the folks at Southwest Research Institute and the people from all over NASA that have been participating, and it'll be a test using all reinforced carbon panels and T-seals from eight, nine and 10. We're going to take – in fact, it's in the process right now – of panel eight from Orbiter 104, which is Atlantis. It has 27 flights on it, so it will be very close to the type of flight history that Columbia had. Just as a note, there's a new panel eight on order since this was the one spare in the fleet, and delivery time there is probably something, six months or more, but that is probably – matches up reasonably well with the return to flight schedule.

We're going to test this panel eight per what flight specifications, the same process that panel would go through if it is being used and created for the first time by the vendor. These test here, visual, x-ray, eddy current and so forth. If there's time to fit it in, we'll do this so-called thermography test. And the schedule is the following: we're going to test Friday, a shot at fiberglass panel eight. That's the 27th. If necessary, we may do another one on June the 30th to be sure that we've got the positioning and the footprint and the velocity just right. And the schedule right now for doing the all RCC test is July the 7th. We believe this is a pretty firm date. Unless there's a big surprise, all of the testing and preparation and so forth should line up to where we can do this very important test on July the 7th and, hopefully, add to our knowledge about the most probable cause of this accident.

That concludes my remarks. I'd be happy to take questions.

MS. BROWN: Okay. I think we're going to try to take a couple questions from the phone bridge first, just because we're going to lose the bridge in a few minutes. Bill, are you still there?


MS. BROWN: Okay. Do you have a question?

UNIDENTIFIED MAN: I do. Scott, just a quick one for me. Since you're taking panel eight off of 104, are you going to do any NDE testing to kind of get the before and after, if you will? And if not, I mean, isn't that an important thing to do?

MR. HUBBARD: Right, yes. You probably don't have the slides there with you. I believe they're being posted to the Web site. But, there is a – on the last chart there, that we'll do non-destructive evaluation just as the – at the vendor site, just like they would do for a brand new panel, to establish a baseline, and that includes a visual inspection, an X-ray, what they call eddy current, which is a type of electrical test, as well as ultrasound. And even though it's not done as a normal vendor inspection, if we can work in a thermography test – that's an infrared test – we'll do that, as well, so that we've got a good baseline.

MS. BROWN: Gina, are you still on? Okay.

MR. PHIL CHEN: Phil Chen's here.

MS. BROWN: Okay, Phil, go ahead.

MR. CHEN: Okay. Scott, early on, there was talk about aging in the RCC panels being a possible cause. Admiral Gehman's example with the termites – is that still being addressed? I'm thinking – are you thinking about acquiring a virgin RCC panel to see how different it is from one which has had 27 flights on it?

MR. HUBBARD: Well, what we're doing in this test is trying to establish the most probable cause of the initiating event and trying to connect the dots between the foam shedding and the hole that was almost certainly in, say, the bottom of panel eight or nearby. And so, we're focusing on trying to create the flight conditions as closely as possible, and to us that means using aged RCC, the same flight history, if possible, as Columbia. I don't have any doubt that NASA and the shuttle program in the future will probably carry out a very extensive series of tests of material of different ages. I know that there are – is work going on already to look very carefully at the kind of sub-surface defects that would occur as part of aging. But, I believe that's future work. What we're focusing on is trying to re-create the conditions of the accident.

MS. BROWN: Anybody else on the phone bridge?

MR. KEVIN SPEAR: Laura, it's Kevin Spear.

MS. BROWN: Okay, Kevin, go ahead quick.

MR. SPEAR: I'm wondering, what do the models say about the transfer of energy in an all RCC system versus an all fiberglass system, the rate and the amount of transfer of energy?

MR. HUBBARD: The models have been pretty good in predicting strain, that is to say how much flexure and bending and tension are these under, and they have not been particularly good at predicting breakage. We have a case where something broke in the test on RCC panel six just above the so-called allowables – that's what the manufacturer provides. But, another place in the panel, it was three times the specification and didn't break. That's why we are making this test as much like the real wing-leading edge as possible. The difference between tests, I think, is an important way to be able to translate from fiberglass to RCC. We can't, in detail, make the connection, but the fact that one set of panels shows this transfer of energy, that the models show that the stress accumulates in a similar way, I think gives us confidence that we're doing the right thing in putting an all-RCC panel together.

MS. BROWN: Anybody else on the phone bridge? Okay. Sorry if we lose you guys, but I believe you can watch the Web cast version to follow along. Why don't we do questions the same way we did before? Todd?

MR. TODD HALVORSON: I'm Todd Halvorson of Florida Today. Interpretation in the debris in the sensor data in evidence now seems to come to the conclusion – Mr. Tetrault said that foam hit was the most likely cause of the accident, or that it was highly probable that foam cause was initiating the event. In light of your foam testing to date, where do you stand on that?

MR. HUBBARD: I think that we have – I agree completely with Roger, that, based on the data from the debris and the sensors and the way the wires burned through and so forth, that there had to be a breach probably somewhere in the bottom of panel eight, maybe in the so-called T-seals, you know, these things here that are either side of a pane. And we also know without a doubt that a piece of foam that weighed about – less than two pounds came off and hit at about 500 miles an hour. The thing that I'm trying to do with these tests, and I think the board is looking at this information, is a piece of that most probable cause is to connect that dot from foam to breach. And so, that's where I stand.

I think that the panel six test that we did showed that we got a plausible failure scenario. We created a substantial crack five inches long, but we haven't created yet a breach that is like what has been described by the debris. So, you know, maybe I'm one step behind Roger in coming to a conclusion but, as Admiral Gehman said, that's part of our discussion here is to put all the data on the table and see if each and every one of us agrees on that adjective of most likely, highly probable, so forth.

MS. BROWN: Mark?

MR. MARK CARREAU: Mark Carreau, Houston Chronicle, thanks. So, what do you predict is going to happen on July the 7th to connect the dots? What do you think you need to see? And I'm – I guess I'm talking not only about panel eight itself, but if you're going to measure outboard of that, what sorts of things do you think you need to see to connect the dots?

MR. HUBBARD: Based on the tests on panel six, you know, where this piece of information – what it adds to the total discussion about plausible to most probable, I think will depend on the extensiveness of the damage. You know, is – we see a whole network of cracks? You know, do we see something that runs across the T-seal? You know, given that our models have been pretty good in forces but not so good in breakage, I'm not going to go out and say what I would predict there. I'd rather let the system respond to us and tell us, but I think that, you know, from a crack to multiple cracks, or maybe fractures or breakage, will help us set the adjectives from, you know, plausible to highly probable.

MR. CARREAU: It doesn't sound like you're saying there has to be a hole there.

MR. HUBBARD: I don't think that there has to be a hole as a result of the initial hit. Remember, this occurred 82 seconds into a flight that had several minutes to go, and had to go through more heating, more vibrations, sixteen days on ordinance and so forth. And, you know, how these fractures propagate and so forth is something that needs to be understood, and it is not understood today.

MS. BROWN: Marcia?

MS. MARCIA DUNN: Marcia Dunn, Associated Press. This is coming up pretty close to – with the reports coming out, and I'm wondering if – are you under the gun to get this out of the way before the final report is out? And if you can't do it, for whatever reason or it's an incomplete test, are you prepared to go with all the tests to date, minus the last one, and put that into the final report for the conclusion?

MR. HUBBARD: I think that what – it's a very good question, and we don't want to rush an important test. You know, we're taking our time to be sure that – it's taken months to get to this point, to build the right structure, to instrument it properly. We added in this instrumentation on panel eight that we hadn't added – thought of before because everyone was focused on the panel or the T-seal. And what we started to realize was it's the whole system. And so, we've tried to be careful about doing a good test to establish whether this was the most probable initiating event. We haven't made a science project out of this in the sense of understanding all of the properties of reinforced carbon. That will come downstream.

What – if, for some reason, we came to the point where the test simply couldn't be done, or whatever, then I think that the board would look at all the data on the table and would make – come to some consensus about whether the – this was the most probably initiating event or not. I think, as Admiral Gehman has pointed out several times, you know, this proximate cause discussion, this direct mechanical cause, is only one part of a much larger discussion about the shuttle program. At this point, I think that the date of July the 7th, in terms of conducting the test, seems to be pretty good.

MS. BROWN: Kathy?

MS. KATHY SAWYER: Kathy Sawyer, the Washington Post. Scott, do you – you talked about the – you showed us the foam stuck in there, and you said earlier, I believe, that this had not figured largely in your predictions until you saw it stick in the first test.


MS. SAWYER: Is somebody else working on the possible impact – not real impact, but the possible effects of the foam remaining stuck during launch, during – arrival in orbit, during maneuvering, etc., and is that playing, also, into other – these studies they talked about earlier today about the launch – properties of the launch?

MR. HUBBARD: Yeah, that's a good point. Up until we had done the first set of tests and seen this mechanism that, I mean, seems obvious in hindsight, of course, you know, if you punch in a panel that's going to get caught underneath, but this is why you do the experiments. It's only obvious in hindsight. As soon as we did that, then the people who were thinking about how the heat got in and propagated through the wing began to say, "Ah, aha, you know, this makes – this is a different way to create a slip." You don't have to have an entire T-seal missing. You stuff this foam underneath it. You wedge something aside. Maybe the pins underneath get permanently deformed – and I'm hypothesizing here – but it's another mechanism to create a slit to let in the heat. So, from that perspective, I think the test has told us something that we were not aware of in the beginning, or hadn't thought about.

MS. SAWYER: (Inaudible).

MR. HUBBARD: Yes. There are aerothermal – the analysts that do the thermodynamics and the aerodynamics are looking at slits and how big would one have to be, the total area and so forth, in order to let enough heat in to create the kind of damage and the time sequence that had been observed elsewhere.

MS. BROWN: Ralph?

MR. RALPH VARTABEDIAN: Ralph Vartabedian, L.A. Times. In past weeks, there's been a lot of discussion about panels five, six and seven, and particularly the T-seals between panels five and six as the possible breach point. And I recall Dr. Widnall had described whether half a T-seal could be missing and whether it would replicate the pattern of the mystery object re-entering the atmosphere. And at some point, I believe that's why, if I'm not mistaken, although I must be, that's why you picked panel five for your initial – or panel six for your initial RCC tests. At what point did you begin to go from panel six to panel eight as the most probable breach, or am I missing something?

MR. HUBBARD: No, you've got it exactly right. What you've experienced with the board is, you know, a certain kind of physics in action, I mean, research and development on the fly. We have taken the data, the best data of the shuttle program and that NASA's come up with. They've refined it. The tests have been refined in response to that. If you recall, the very first tests we did were against the main landing gear door, and that was because some of the early indications were that was where the foam hit. As the visual analysis of the film and the video got better, got cleaned up and de-blurred, as the physics trajectory analysis got added to the – and married with the visual analysis, it became clear that the footprint probably was not across – if you remember some of those early pictures, it was something like this coming across here, and it actually moved – the line of most probable impact moved over here.

At the same time, the debris evidence began to come in. We were finding some things and not finding others, and the timeline of the sensors as they burned, the wires burned through and so forth, began to come in, as well. So, all of that led us to the point of testing, you know, panel eight as the most probable, and panel six has turned out to be a good lead-in to that to understand all the other system effects.

MR. VARTABEDIAN: Is this the first – I know that panel eight was always looming up. There was a lot of evidence. Is this – has there been some sort of shift just in the last two weeks from panel six to panel eight?

MR. HUBBARD: No, no. We've had this – this shift occurred maybe, you know, a month and a half or two months ago, yeah, something like that. But, the – and in fact, at the point where the data was starting to shift from panel six to panel eight in the analysis of all of the trajectory data, we weren't sure what the right thing was to do in building up this test article. So, after a lot of discussion, I said we ought to plan for maximum flexibility, and that's why this whole thing got constructed, was because six, eight – you know, six to nine, so NASA got 600 pieces and, out of seven different centers, put together so we could have some significant flexibility to test the whole range.

MS. BROWN: Frank?

MR. FRANK MORRING: Frank Morring, Aviation Week. Scott, will this data be used beyond determining the cause, or probable cause, of the accident? For example, in recommendations that the panel might make in hardening leading edges or other areas?

MR. HUBBARD: Yes. The data certainly is going to be used for the future, and I think that we've already, as a result of doing this investigation, caused some new data to be generated about the properties of reinforced carbon and all this – we've got hundreds of sensor measurements that are – we've analyzed only the most important ones. That'll be part of the database for the future. And one of the things that we're looking at, thinking about in the preliminary or interim recommendation category, is whether it's possible to establish thresholds, you know, that so much energy represents a certain type of damage and concern but, above this energy, it represents a very serious concern. So, that data is playing into those considerations.

MS. BROWN: Traci?

MS. TRACI WATSON: Traci Watson with USA Today. Along the lines of Frank's question, have you considered whether it's possible to armor the leading edge? You know, NASA's always assumed this area is tough, but is it even feasible to make it tougher?

MR. HUBBARD: It is. That's a good question for the Materials Science people. The reason that this is reinforced carbon is because that was, at the time, the best choice of material that you could obtain that could withstand – and I have to qualify withstand. It's a little complicated – but, let's just say withstand 3,000 degrees Fahrenheit. It's hard to find materials that are both tough, workable and withstand those kinds of temperatures, and this carbon material, when it was being designed in the late '70's, was the best available. I think people are going to go back now and think about whether, for the next vehicle, some other material might make a better leading edge. I think for the Orbiter, as it stands, you know, they need to work with what they have and, as you heard, we're thinking about some recommendations about how you might do an emergency repair.

MS. BROWN: Paul?

MR. PAUL RECER: You're going to do this on July the 7th in San Antonio in – temperatures of 100, 105 are not unusual in that area. And is this thermal difference –?

MR. HUBBARD: – Are you going to be uncomfortable if you come? Is that – no.

MR. RECER: I've lived there. I love San Antonio. But, if the thermal conditions are going to be different at the test site than they were near 81 seconds into launch, obviously, are – is this any concern that this may bias the results when trying to draw any conclusions?

MR. HUBBARD: Good question. It could have been part of our test team. We asked those questions. We did a series of tests that were done at Glenn Research Center to look at cold, ambient, vacuum, regular atmosphere, sea level, and so forth, and we also looked at the properties of the foam. And this foam has the – withstands on a normal flight -300 degrees on one side and +400 – 300 degrees on the other side. We looked at the temperatures in the barrel. We looked at the thermal coefficients, you know, the various ways in which the foam can respond, as well as the reinforced carbon, and there – nothing jumped out at us as being anything that would bias the test. We did think about that. In fact, the first couple of tests we did when it was 98 degrees in the shade, you know, I raised that very question, and none of the data we have has indicated that it's going to create a false answer.

MS. BROWN: Okay. Earl?

MR. EARL LANE: Earl Lane with Newsday. Given the kind of face motion that you saw in that test number three, I mean, what can you predict might happen with that RCC panel number eight?

MR. HUBBARD: Direct comparisons between the detail properties of fiberglass and the detail properties of carbon – reinforced carbon are hard to do. That's why I emphasize the difference between the tasks as being the more important thing. Reinforced carbon is stiffer, but not as strong, as to say it's more brittle. So, I can't predict exactly how much it would flex. What I can say is that, comparing fiberglass panel six in that first test and fiberglass and reinforced carbon test in its first test, it was a half an inch of motion versus 1-1/2 inches of motion. Now, is it a factor of three? I don't know. You know, I mean, that is why we're going to do the experiment. But, I think if the comparison holds true, we would expect a lot more flexure, maybe even to the breaking point, of the reinforced carbon, based on the comparisons, the relative differences in the fiberglass.

MS. BROWN: Alan?

MR. ALAN LEVIN: Alan Levin with USA Today. Scott, could you – I can't quite tell from the photo here where the cracks were. I'm assuming they're on panel six, but if you could take us through where they were on your model. Also, did you do any non-destructive tests in between the tests so it was – to give you a sense of whether there was any un-visible internal damage?

MR. HUBBARD: We have done a fair amount of non-destructive evaluation on the reinforced carbon panel. We have done some, but less, on the fiberglass, because what we were looking there for was the total response and how the one test compared to the next one. But, just to take one of these panels here, if you look at the hardware, and this is – says fiberglass test three results continued – I don't know if you can back up to that one or not. But, it is the lock side that is – you know, there's two sides to this, what they call the slip side and the lock side. The lock side has the groove, and it's inboard – inboard lock side, and the – it was up in here along this rib that you had the eight-inch crack. And let me be sure I'm saying that the – yeah, it's from the lower flange, so, remember, we aimed at the bottom part of the panel. So, it's down in here.

MS. BROWN: Okay. Is that – okay. Matt?

MR. MATTHEW WALD: Scott, Matt Wald with the New York Times. The clocking angle on the actual accident, which is, of course, unknown and unknowable, does this raise the possibility that, whether the thing broke enough to produce a breach in the accident, depending on the randomness of the angle at which this tumbling block struck the leading edge?

MR. HUBBARD: Well, I don't know – I can't give you an exact answer to that. All we can do is speculate. We do know from the visual evidence that this piece of foam was rotating at about 18 times a second, and we have – because that has the ability as it slaps in, you know, not just the vertical force but the rotational force as it slaps into this panel – we have adjusted the angle of the shot to try to accommodate that, to try to add that extra force in. We don't know enough about the range of sensitivity of this material to be able to give you a more definitive answer?

MR. WALD: (Inaudible).

MR. HUBBARD: I'm sorry?

MR. WALD: Probably won't find that out (inaudible).

MR. HUBBARD: Yeah. What this test is trying to do is trying to say, you know, how would you create local force? You know, I mean, this is – oh, by the way, somebody asked what's the difference in size. You can see that this panel – let's take panel six out here, and this is panel eight. You can see the relative difference in size, and I went and looked it up. This is about 19 inches by 19 inches, 19 inches wide by about 19 inches tall. This one is about 28 inches wide by 25 inches tall. So, that gives you a sense of – I don't know who asked the question of the difference in these. And what we're trying to do is determine, since many other pieces of evidence say this is the most likely breach location, how do you transfer significant force right here? And so, that's why we've picked the conditions we have.

MS. BROWN: And I should point out that this model was made without the T-seals just to show the general size and the area of where the panels are located.

MR. HUBBARD: Right, yeah. This is not exactly representation only. For purposes of clarity.

MS. BROWN: Richard?

MR. RICHARD HARRIS: Yeah. Richard Harris from National Public Radio. You mentioned that panel eight, that when you test it, it's coming off of one of the Orbiters. What about the adjoining panels? Do they all – are they essentially going to dismantle, cannibalize from the Orbiters to do this and, when they're done, do you – would those panels go back on the Orbiter, or will have to re-manufacture all of them?

MR. HUBBARD: Tested panels are not going to go back on any flight vehicle. The panel nine is – there are about four spares in the fleet of panel nine, so that is not an issue. We have a panel with the same kind of flight history, that there – you know, is – and I think that panel was taken off of Discovery, but, it has a spare in its place. The decision process to use panel eight was complicated by the fact that there was only one spare in the fleet. So, although they interchange these panels, in effect, we are using that spare. But, as I said before, there is another one on order. The lead-time is something greater than six months, probably, to produce one. But, it's our sense that that probably corresponds reasonably well with return to flight. So, it – the fleet should end up with another spare in time.

MR. HARRIS: And 10?

MR. HUBBARD: Number 10 I believe also came off of Discovery, but it's also one where there's multiple spares.

MS. KRISTY NABIELSKY: Kristy Nabielsky (sp) with N.K. (sp) newspaper. If you could remind us at what angle the hot gases hit the Orbiter, or where – is it the underside, the upper side – the hot gases hit the Orbiter upon entry? Would it be in the same place where you found the crack in this last test, the eight-inch crack?

MR. HUBBARD: Right. We have been shooting the foam at the bottom side, which is where the visual evidence says that it hit. That's what you see on the film in the video from the accident. And we created a crack in the first shot against the RCC down here at the bottom of the wing. And it's down in here somewhere that the breach occurred that let in the hot gas.

MS. NABIELSKY: (Inaudible) upon entry, the angle of the entire Orbiter?

MR. HUBBARD: Oh, it's at an angle of about 40 degrees.

MS. NABIELSKY: (Inaudible).

MR. HUBBARD: Yeah, it's coming to the underside of the wing – well, and then it (inaudible).

MS. BROWN: Okay, Gwyneth?

MS. GWYNETH SHAW: Gwyneth Shaw with the Orlando Sentinel. You mentioned kind of a general lack of understanding of how these cracks or damage would propagate during the rest of the ascent during orbit and the early stages of re-entry. Have you tested panel six to kind of see what happens to the damage on that? And if so, how long does that take, and how would that affect your results from panel eight?

MR. HUBBARD: The process of evaluating panel six after it was tested, it was thoroughly evaluated prior to the test. The panel six CAT scan – and it is the same process that's used in medical diagnostics – has just been completed. They did not find the people that did that work. Any anomalies, any unusual features in the panel other than the crack that was created as a result of the test. Given that that took days to do, and we wanted to get the best pre- and post-comparison, we've been very careful not to take the panel and flex it or torque it or, you know, in any other way, you know, cause it to break, because we wanted to preserve that. The evaluation will go on of how that crack could propagate well-past the report of the board, and I think it's part of the ongoing understanding of how these can fail and in what way with how much force.

MS. SHAW: Have you done anything to subject it to forces that you would see in the rest of the assets? I mean, in terms of how much – if it's a very small crack at the time of the strike, what happens to it after that?

MR. HUBBARD: No, we have not done any testing on that. We've just – like I said, we just completed doing the post-test X-ray.

MS. BROWN: I think one thing I should point out is the Admiral had said that, when the report comes out, it will be the final report, but some of the appendices may take several weeks to follow that report. So, when the report is put out, we don't expect to have all of the supplementary material available on the day we release the final report. It may take several weeks after that to release, for instance, some of the final reports on the testing and evaluation, and some of the other appendices. So – Paul?

MR. RECER: The difference in the availability of spares for nine and 10 versus eight suggests that eight has had a higher rate of replacement than the other panels. Is this true and, if so, why?

MR. HUBBARD: No. Panel nine is the one that gets replaced the most. I mean, only three panels on Columbia, for example, were ever replaced. They had gone in for examination and for a certain level of maintenance and repair, but only three panels were ever replaced. So, panel eight – I can't speak to why there's only one spare in the fleet. It may have just been the result of focusing on the other panels that were in, you know, higher heating area or something.

MR. RECER: (Inaudible).

MR. HUBBARD: It's the highest heating area. Nine is the one that sees the highest temperatures.

MS. BROWN: Alan?

MR. LEVIN: I'm sorry, (inaudible). The RCC test article is now 100 percent RCC?

MR. HUBBARD: Correct, yes.

MR. LEVIN: So that you can assess the system effect?

MR. HUBBARD: Correct, yes. I didn't make the clear. That was one of the major findings of these last two tests we did, was to determine that there is a system effect that we have to account for, and that the panel eight is the target, and that to really get it, since the models have not been predicting the breakage very well, although predicting the stresses pretty good – we really need to have this be as much like the real thing as possible. Therefore, it's all RCC, T-seals, panels, everything. Five, six and seven were not in the equation any longer. Did I answer the wrong question?

MR. LEVIN: (Inaudible).

MR. HUBBARD: Yeah. They'll – well, they're going to be downstream from the impact – I mean, upstream from the impact. The impact's going to be – for the next set of tests is going to be right here, and the force goes this-a-way. But, they will be there, but not RCC. These will –.

MR. LEVIN: – (Inaudible) some anchoring from the panels upstream (inaudible)?

MR. HUBBARD: It's on the slip side, so, yeah. Now, they – the connections that we've seen have been the transfer of force downstream.

MR. LEVIN: With (inaudible)?

MR. HUBBARD: Upstream, correct.

MS. BROWN: Okay, Mark?

MR. CARREAU: Thank you. I'm Mark Carreau, the Houston Chronicle. A couple of times, it's been mentioned that panel eight is unique. I don't know if you even want to use that word for any of them, but it's got a trapezoidal shape. It's where the wing starts to really make that cant outward. Is that a factor in any of your assessments that you're making? Is there anything from the physics of the different shape and the translation of forces just through it that are concerning that might have made it more vulnerable, or anything in your findings so far?

MR. HUBBARD: I don't have any really analytic answer to the question. All I've got are the kinds of things that the structural engineers and the physicists spat around and talked about. We have noted the unusual shape, the fact that this is the largest panel and, therefore, given the structure of Columbia, as the largest distance between the supports, it's not supported all the way across this 28 inches or so. And that – you know, if you just think about, you know, breaking a board, you know, if you've got two supports very far apart and you put that impact right in the center of it, you can create a far greater deflection than if you move the fulcrum – you move the support point close together. That's as far as our thinking has gone, although they're creating good models – mechanical engineering models of this for the analysis.


MR. HUBBARD: Yeah. Columbia has a slightly different structure – sub-structure than the newer Orbiters.

MS. BROWN: I'll take just a couple more questions here. Marcia?

MS. DUNN: I was wondering if you had, after each test, when you've gone up to look at the craft, if you'd had a space helmet on and a space suit, and were just sort of floating there looking, how visible would this be on inspection by an astronaut? Would it be readily available? Would you have to really spend a lot of time there trying to see what the problem was?

MR. HUBBARD: Well, I mean, you've got a couple of hypotheticals piled on there, so it makes it difficult to give you a detailed answer. You know, the crack on the last fiberglass test was very, very apparent. The crack on the RCC panel six was less apparent, but it was there. And if you took the time to look at it, you could see it. You know, you had to be reasonably close, but it was visible to the naked eye.

MS. DUNN: And so, you're saying that a space walker would be able to (inaudible)?

MR. HUBBARD: I'm – I don't want to speak for the astronaut corps here, you know. I can tell you what I saw, but, you know, cracks that are an inch long or so are something that you can walk up and see. It's not anything hidden under the surface.

MS. BROWN: Okay. Todd?

MR. HALVORSON: Todd Halvorson of Florida Today, and this may be a stupid question, but it seems to me that the – like the larger cracks and damage that you have found have been on – internally, on the inside of the RCC. Is that correct?

MR. HUBBARD: The one RCC test that we've done on panel six, there was a three-quarters of an inch, or an inch or so, visible on the surface. And then, when we took the panel off and looked underneath, we found that it continued all the way around, you know, for a total length of about 5-1/2 inches. Now, cracks that we've seen with these recent adjustments of the clocking angle and of hitting lower down have been seven inches long on the outside. So, I think it's too – I think you need to – you know, I would stay tuned to see what happens on panel eight.

MS. BROWN: Okay, I think that's it. Did I miss anybody? Okay. Thank you very much. Thanks for all your patience, and the next press briefing is July 8th, and it's going to be earlier in the day than we usually have them. It's going to be at 10:00 a.m. instead of 1:00 p.m.


Back to Event
Privacy Policy Disclaimer Accessibility