|Columbia Accident Investigation Board Roundtable
Friday, July 11, 2003
National Transportation Safety Board
429 L' Enfant Plaza, SW
MS. LAURA BROWN: Okay. At this time, I think we're going to take questions from the phone bridge before we take them from you guys, just so those folks can get tuck a few questions in before we lose the phone bridge. So, let me turn you if you can all stop talking, I'll turn you over to Scott.
MR. SCOTT HUBBARD: Okay. Thank you, Laura.
Good afternoon. As we discussed on Monday, presenting today an update on the impact test that we did in San Antonio at Southwest Research Institute, and there is a package that is being passed around. I have made some further small updates to that package, and I'll try to note them as we go along.
I think the key message from the test that we did was that we are able now to explain a lot of pieces of data that, before, we'd only been able to speculate about. So, if we could go to the first slide actually, the second slide. Hello? Can we go to the next slide, please? Good, okay.
This is, of course, the test setup. We used the facilities at Southwest Research Institute in San Antonio, Texas and, as I think, virtually all of you know, over the last several months we've produced a capability there, together with the people at Southwest and various parts of NASA, to fire foam blocks at around 500 miles an hour using this rig, and we also had it instrumented with about 200 sensors and, in this last test, about 16 high-speed cameras. Let's go to the next slide.
This was the test setup before we fired the foam at about 1:30 on Monday. You can see the wing leading edge setup. It's panels five, six and seven in fiberglass, and then panels eight, nine and ten with their accompanying T-seals in all reinforced carbon, actual flight panels. And then, in the lower right-hand corner in the inset, you see where the target point was. If you go to the next slide, I'll talk a little bit about the significance of all that.
As I said, after considering the fact that our initial tests indicated that the entire system was responding, not just a single panel, we elected to use all flight panels, all reinforced carbon panels and T-seals for the for panels eight, nine and 10, which was the test target. We also turned the barrel 30 degrees so as to present the 11-1/2 inch edge of the foam block onto the curved surface of panel eight. That allowed us, according to the models, to focus the stress further down into the panel where other evidence indicated the breach was.
The angle of incidence at that target point I showed you a minute ago was 22 degrees, which was the 19 degrees as measured from the accident and the curvature of the wing, plus an additional three degrees to account for the rotational energy, the fact that this piece of foam was spinning as it came down and hit the leading edge.
Based on the tests, the previous tests and the analysis, we targeted about six inches further down track from where we were before, again, to try to focus and localize the energy. Even though the total energy on the sheet, or on the front of the reinforced carbon panel actually was the same or a little bit lower than previous tests. It's a question of how you focus the energy. We were had a target of 775 feet per second. We actually measured 777. The 1.68-pound foam block, the nominal that we aim for is 1.67, and then you see the dimensions. Those dimensions get adjusted a little bit with each shot depending on the exact density of the foam as it comes from the manufacturer. So, that was the setup, the test conditions and our projectile.
Before I go to one of the movies high-speed movies of the impact, I'd like to address in the next chart a question that keeps coming up. I've gotten a lot of inquiries from the public, some from the media, both professional and amateur engineers saying, ÒHow could this foam go 500 miles an hour? It only traveled 60 feet.Ó
And so, I thought we what we should do is two things. One is I'll address it very quickly here, but we'll also post on the CAIB Web site a much more detailed explanation for the engineering interest out there, people that really want to understand in detail how this works physically.
The first order answer is we measured very carefully, used all the camera assets, and if you know a camera's running at a certain frame rate and you see that the foam has dropped from here to here at 30 frames per second, it's very simple to go back and get a reasonable estimate of the velocity.
But, in general, the answer to how this 500 miles an hour happens is the following: the shuttle, of course, is flying at mach 2.4. That's about 2,300 feet per second, or about 1,600 miles an hour. The foam has a very low what's known as a ballistic coefficient. That's how it responds to air. Its ballistic coefficient, if you were to examine the foam block we use, is much closer to this sheet of paper. It's nothing like dropping a pencil or a cannonball.
So, it responds to the air stream when it came off the bipod ramp by actually slowing down, much as this piece of paper falls very slowly. So, in the 60 feet, it actually went from traveling with the shuttle at 2,300 feet per second to slowing down, by virtue of being in the air stream, to 1,500 feet per second.
So, the wing actually ran into the foam at a relative velocity then of 800 feet per second, or something like 500 miles per hour. So, I'd like to ask the media folks here to help us explain this to the public so that they clearly understand what's going on. It's like traveling with two cars together. The car in front of you all of a sudden slows down to 30 miles an hour. You're going 60. You're going to hit them with a relative velocity of 30 miles an hour.
So, let's now go to the next piece of information, which is one of the high-speed videos. I guess it takes a minute to load up. This is the one from camera site three. It produced, as you know, the very dramatic 16-inch hole on Monday. You can see the foam block there impacting at the target point. It was within a quarter inch or so of that circle of the center of the circle that we drew, and I'm going to show you a couple more movies that will help us understand how this damage occurred. One of the things to look at here is these will all be posted on our Web site, too, so you can download them.
One of the things you can notice is how the foam block broke up. You can see that it was a series of small shards, but if you look just as it exits the frame of view here, you can see that there's one or two big pieces that keep going. And as we reviewed the film from the accident, that's, in fact, what we saw, is a spray of foam, but a couple, maybe two or three larger pieces, that exited under the wing. So, the appearance of this looks very much like what was observed from the film of the accident.
Okay, let's go to the next one, which is the damage that many of you saw. Very dramatic hole below the apex of the wing. One of the targeting considerations was to have essentially no foam going over the wing-leading edge, and this was part of the consideration where we targeted, in addition to trying to focus the force lower down where we think the breach occurred from the debris.
If you go to the next slide, you see some measurements. This is new information. People have been working very hard this week down in San Antonio to help us evaluate the sensor readings, the actual measurements, and some of the other debris created by the broken reinforced carbon, and I'll show that to you here in a minute. So, as you can see, it's actually a little closer to 17 by 16 in the longest dimensions, but has edges of about eight and 10 inches, respectively.
As was said in the press conference a few minutes ago, our view of this the Board's view of this is that, given the range of velocities, the range of estimates for the size of the foam block that fell, and given the range of variability in this reinforced carbon material, this hole is right in the ballpark. It the one that matches most closely with the burn-through of the wires and so forth is probably smaller than that but, given that fact these other estimates vary in some cases by 30 percent or even 50 percent, I regard this as being essentially the same thing as the hole that was probably there. Certainly a very clear connection between the foam and the breach.
Now, if we go to the next one, you're going to see a movie that you haven't seen before. It is a little bit darker than usual, because this is one of the very highest-speed videos. This is being taken at 7,000 frames per second, and it's interesting for a couple of reasons. One is, if you look at the lower left, you will see the as it loops back through, you will see the compression and the bending and flexing of this carbon panel, which is very brittle. So, flexing it by as much as an inch or so see the gap open up there on the left and then it springs back. You see the demonstration partly of the force of this foam block.
The other thing that's interesting is that the foam is not breaking up immediately on contact. It is actually pushing this force into the panel, and then it as it hits the edge of the T-seal, that's how it and contacts the ragged hole there, that's what begins to initiate the breakup. You can also see in both of these the broken pieces of reinforced carbon panel that are driven back into the inside of the leading edge.
If we go let you watch that one more time sort of slaps across there and pushes its way in and breaks the panel. It's very much an application of the force over a fairly large area.
If we go to the next one, which is one you've seen before, it's the same view now from the inside, and it shows how it's broken in the front. You have that big piece come flying through, and then the rest of the debris. I'm going to let this cycle once or twice so that you see that first big piece that comes through. Watch the lower left of that piece, and look for the little curvature as it departs. See that? I have a freeze frame of it that I'll show you later. This, we believe, is a very likely candidate for the second-day drift-away object. It seems to match quite well all of the radar cross-sections.
The other thing, of course, is just the tremendous force and violence of the impact. See foam being pushed inside? One thing I should note is that, unlike the actual Columbia, of course, the inside of this is heavily instrumented. That's a lot of what those little white dots are, and there are all manner of cameras watching this, one of which got broken by the impact. Those wouldn't exist, of course, in the actual accident from the in the Columbia.
All right. So, go to the next slide. Here's what we've no, back up one, please. There you go. There were a number of large pieces inside the panel. I'm going to focus on the one that we just saw. In the left-hand side of the slide, you can see a freeze frame from that high-speed video. It shows this fragment from the impact, including the lip from the panel rib. If you go to if you go to the model here, you take off the T-seal.
Most of you remember there is a so-called lock side that's this groove here and there's the slip slide, the smooth area here. What got impacted was down here, flying in this way, broke this big hole, and the chunk here that included this lock-side rib is what went flying back into the inside of the leading edge. This curve of lip here, plus the chunks that are here, are what make it a very plausible candidate, or a very compelling candidate, for the second-day object.
As you see there, we listed a couple of the characteristics. After they measured dozens of different possibilities, the people at the Air Force lab and Lincoln labs concluded that a high-probability candidate was a piece of reinforced carbon panel greater than 90 square inches, roughly square, with about a third of an inch thickness. You can see two pieces of this one that came flying through. One is 86 square inches. The other is 75 square inches. If those hadn't been broken if that hadn't been broken in two by the impact with some of the cameras and stuff on the inside, it would have made a, you know, even larger piece. But, even by themselves, they are certainly very close to the estimated drift-away object.
The thickness is in the right range, too. The carbon panel eight has thicknesses in various areas. It's thinner in the face sheet. It's thicker at the edge. It has thickness from 2,300ths of an inch to 3,600ths of an inch. So, again, it matches very closely with what the radar cross-sections were measured of the flight objects. So that the summary there is that it looks like we may have identified where this came from, or certainly a very plausible candidate.
Okay. Let's go to the next slide, tell you something that's brand new for all of you. As we took this apart, the technicians and engineers found that the T-seal lug was broken. Now, this is interesting for a couple reasons. This is a piece of T-seal here. This is the so-called lock side. You see that. This is the flip side. And this lug here is quite thick. It is, you know, a good third of an inch thick or more, and it's many, many plies. It's maybe twice the number of plies that there are out in the face of the panel. And this got broken, as you can see.
This seems to explain some of the debris that is on the floor down at KSC. It looks very much like that, during flight, the a broken T-seal between panels eight and nine was allowed to flop up and down and, in so doing so, we had a T-seal here that was loose, and it looked like it flopped up and down because there was scoring on the inside here of the ribs that could not have been created by very long-term exposure. It seems to have required intermittent exposure, the different type of scoring or heating than you see in some of the other areas where things have been eroded to a knife-edge.
And this has been a puzzle for quite some time. How could this have happened? Well, we think we have a reasonable explanation now. It broke this lug that loosened the T-seal. That allowed the T-seal, then, to sort of hop up and down, so as the hot plasma intruded, as this came in through the atmosphere, it would have intermittently exposed the region underneath. This single test, together with what else we know, is really allowing us to really connect the dots even further and draw some lines between various pieces of evidence.
If we go to the next slide, see just a sampling of the cracks. Three inches, four inches, there are cracks on this panel, and panel eight up to 11 inches long. The significance of that is that these are through cracks. These pieces are literally just barely hanging on.
So, it is not far-fetched at all to think that, during re-entry, particularly if maybe the breach was slightly smaller, that we had this extensive cracking, that as the dynamic pressures and the temperatures built up, these pieces that were just hanging there could come loose and become some of the shedding events.
Remember, we had some 16 or so observed events where something was shed from the Orbiter, flashed brightly or departed, and a series of cracks with this type of high-temperature material could have produced that phenomenon. So, we think that, once again, this test is allowing us to make some connections to some other data we had previously.
The next I want to talk a little bit about the sensor measurements. This is a result of the analysis over the last three or four days. You see on the left there panel eight. The numbers next to those white dots are the measurements of force in thousands of pounds per square inch, what the engineers called KSI. And as you can see, they vary quite significantly from relatively low over near the side of one rib down here, just a few thousands of pounds per square inch, over to where the breach was, where it is upwards of 26,000 pounds per square inch. For pardon? Twenty-six thousand, 26,000.
And for the first time, the models and the stresses and the damage are starting to line up. I mean, this gives me, as a scientist, some feeling that now in the future, as NASA carries this forward, they'll be able to match up the predictions and learn you know, create a model that could be used to evaluate things in the future to understand more how this system responds.
The predicted maximum stress was around 30,000 PSI. What was measured was 26,000. I think that's a very good agreement. The important thing from understanding that understanding the breach is that, in this area in here where the breach occurred, we exceeded the original design values of this material by 50 percent or more, and that, of course, was more than enough to create the hole.
And based on the original design values for brand-new material, it indicates to me that this impact would have broken even brand new RCC. So, while aging of the fleet and aging of RCC may well be a long-term maintenance issue, at least in this test with this particular foam block, we had more than enough force to break something even if it was fresh off the factory floor.
So then, the last chart here, then I'll be happy to answer questions, is sort of a summary of where we are thus far. I think we have some pretty clear evidence of the foam impact as the initiating event for the leading edge breach. As we've discussed a few times, the size of this is definitely in the ballpark that was indicated by other analysis. I think we've got a pretty good candidate for the second-day drift-away object. We've demonstrated a whole maze of cracks where the material was literally just hanging there. That could well be the source of debris shedding during re-entry and, as I talked about the hopping up and down of the T-seal, that helps us to explain some of the odd thermal or heat scorching characteristics of the rib underneath it.
Now, what's next? Well, the Board has really completed its experimental work. There will be a full test report written on this. The summary comments that I'm making to you now will be part of the volume one of the report. There will be a lot of detail in the appendices so that future engineering groups can look at what we did and evaluate the data, and perhaps build on it.
What NASA tends to do, based on discussions with people at the Johnson Space Center is, in the general sense, to reduce this data, fully understand it, and then start developing a new test plan that's going to evaluate what I've been calling the damage thresholds, what size of piece at what velocity at what angle represents a real threat to the Orbiter, and obviously that's needed for future considerations.
So, that concludes my comments, and I'll be happy to take questions.
MS. BROWN: Let me take a few questions from the phone bridge quickly, because we're going to lose the bridge in a few minutes. Dan, are you still there?
MR. JAY BARBREE: Hello, this is Jay Barbree.
MS. BROWN: Okay, Jay, go ahead.
MR. BARBREE: Okay. Mr. Hubbard, I was watching here with a lot of interest. If you remember when Story Musgrave spoke before the Board, the quintessential space-walker, the first man to walk from the shuttle, did six or seven of them, the Hubble, that he is regarded as probably the best space-walker ever in the history of the space program. He said that he choreographed that he could have made a Òno-brainerÓ space walk in 15 minutes. If they had used the two astronauts on board that had been trained for an emergency space walk and had gone over the side, would they have had any problems whatsoever in seeing this hole, or would they even have had any problems seeing it with the spy satellite assets that were up there?
MR. HUBBARD: I don't think that astronauts on a space walk would have any difficulty seeing a hole of this magnitude. And as what other assets could do, I'll leave you to Admiral Gehman's comment earlier, where he said he thinks they're assets that could do the job. But, it does depend, I hasten to say, on, you know, how far cameras are away on the contrast. Remember some of the pictures that I showed, where you had a black hole against a very dark gray leading edge.
MS. BROWN: Okay, Gina, you still there?
Okay, anybody else on the phone bridge?
MR. PHIL CHEN: Phil Chen here.
MS. BROWN: Okay, Phil, go ahead quick.
MR. CHEN: Okay. Scott, with the cracks that you had, what would be the size of the pieces, based on this particular test, that could have come off as early shedding events? Any idea on estimate of the size of those pieces? And do you have enough area to account for all of all 16, or whatever, events?
MR. HUBBARD: I haven't done a detailed analysis on this. It just the point of showing that slide was to demonstrate the plausibility of it. We had, as you saw in one of the charts, a number of pieces on the inside that were along the order of a square foot or so. If some of these other pieces came away, you could easily create chunks as large as that, a square foot or more, and I'll just leave it at that. It'll take a lot more analysis of what we've done here to be able to see if you can match these up with specific events, but I think the plausible explanation is there.
MS. BROWN: Okay, anybody else on the phone bridge? Okay. Sorry we're going to lose you guys, but we'll I guess you'll be there as long as possible.
Why don't we start down at this end on questions again, Earl?
MR. EARL LANE: Earl Lane, Newsday.
This flapping T-seal, the location, again, was between eight and nine?
MR. HUBBARD: Correct.
MS. BROWN: Okay, Mark?
MR. MARK CARREAU: Mark Carreau from the Houston Chronicle.
And I have a question in the same vein: could you show on your model where the lug in the test broke up or down? And then, was that are you surmising that that's the same sort of thing that could have happened on Columbia, or you're just saying that a lug break would explain that phenomenon that you saw? I guess I wasn't clear exactly what broke on the test and what you're saying would have broke on Columbia to produce this effect.
MR. HUBBARD: Right. What I'm saying, or saying at least makes some sense out of some data that we've seen before that we didn't know how to explain, is the following. Let me start with the T-seal itself, and let me, if I may, back up to that picture, which is back a few slides from the end there. If you go one, two, three, about four slides back from the end. There you go. Go ahead one there you are. Stop right there. So, the T-seal, which is this is a piece of real T-seal here, this the attachment lug that's down at the bottom broke, and you can see that in the figure there, and what we're then so, that's a fact, that broke, so in the test, and you can see the fixture that it was in in the lower right, and you can see then it would have been free to move.
So, what our conjecture is, then, is that, since that happened, that could have allowed this T-seal then to oscillate, to move up and down, and that would have intermittently let hot gases come in and out. So here, the blocked the breach would lead the gases in through here to the other side, but what we've observed on the debris on the ground in the hangar at KSC is some unusual scorching and scoring of the rib that sits underneath the T-seal, and the only thing that we can think of, and now we have a possible mechanism, is that if this was affixed at one end and loose at the other end and was able to bob up and down, that would explain what we've seen, and it would connect the debris story with the impact test story.
MR. CARREAU: I just want to make sure that the lug that broke is between eight and nine, both in the test and that's what your evidence shows for Columbia?
MR. HUBBARD: Yes. We're talking about the T-seal between panel eight and panel nine.
MS. BROWN: Kathy?
MS. KATHY SAWYER: Kathy Sawyer, the Washington Post.
Could you now that you've said these shards of RCC could account for the 16 shedding events .
MR. HUBBARD: Some of them .
MS. SAWYER: Some of them, or that's my question. There was a lot of talk earlier on about zipping tile, and that sort of thing. Is it your do you know more about that, enough to nail it down in your timeline now, and do you have a clear scenario on when that might have started, or is that always going to be an unknown?
MR. HUBBARD: I that I don't know enough to give you that level of detail. What we've tried to learn from this impact test is to see everything that's on here, and then take the other facts as we've got them and try to line them up. And we haven't done the timeline on this at all. I have no idea how long some of these cracked pieces that are just hanging there would take to come loose. But if they came loose and that's, I think, a reasonable conjecture, given the state of this panel then those trailing away during re-entry could explain some of the drift-away events. Tiles coming loose may also explain part of that, as well.
MS. BROWN: Marcia?
MS. MARCIA DUNN: Marcia Dunn, Associated Press.
I was curious as to the material of the lug, and did you what are the sensors showing of the panels the other carbon panels? Was there a ripple effect like you had noticed before? Were they weakened in any way?
MR. HUBBARD: The what did you want to know about the T-seal?
MS. DUNN: The material of the lug.
MR. HUBBARD: This is all reinforced carbon.
MS. DUNN: Even the lug that broke? That's what I'm asking.
MR. HUBBARD: Well, the by the lug, I mean, right here. This .
MS. DUNN: Okay, it's not a bolt or a ?
MR. HUBBARD: No. See the slide there? What broke was the reinforced carbon around the bolt, okay? So, this is the lug, and that you know the thing goes through into the bolt. I didn't mean to use all this technical jargon.
MS. DUNN: And what about the other carbon ?
MR. HUBBARD: Okay, the other stresses. What we measured downstream were relatively low stresses. A quick look is a few thousand pounds per square inch in the adjoining panel, so I think what we did there actually was the right thing to do.
In the fiberglass, we were seeing a huge amount of energy being transferred all the way down the system, and get my other toy out here. When this was all fiberglass and we were firing at panel six, this, having a lot more flexibility, was carrying this load all the way down and then responding to it by making and so, that made us think, ÒAre we really focusing the force the way it did in the real accident?Ó And by making these the stiffer RCC panels, what we found was the force was really localized here. So, I think that that a more carefully done experiment in the sense of better match to the accident.
MS. BROWN: Traci?
MS. TRACI WATSON: Traci Watson with USA Today.
At the beginning of the investigation, a lot of NASA folks, past and current, were saying the RCC was too tough to be damaged by something like foam. Was there some holdout sentiment of that sort that you heard of that was pretty much obliterated by the test?
MR. HUBBARD: I haven't I mean, you're asking just sort of for a personal assessment. This is not a Board conclusion or anything. I think at the beginning there were people that didn't appreciate maybe they didn't do the calculation, or maybe they did the calculation, but it didn't sink in, of how much force can be transmitted at 500 miles an hour by even a light material like foam.
What I did sense is that the dramatic experiment that we did on Monday I think brought home to people in a very visceral and emotional way what most of us have known intellectually, that this was, in fact, very likely, almost certainly, what happened to destroy the Orbiter and lose the vehicle and the crew. So, I think many of us I'll just speak for myself have had a, certainly, intellectual understanding of what force means, and this brought it home in a very dramatic and even emotional way.
MS. BROWN: Okay, Bill?
MR. BILL HARWOOD: Bill Harwood, CBS.
Just two quick related questions. Well, they really are related.
MR. HUBBARD: A Òtwo-ferÓ here.
MR. HARWOOD: Dr. Hallock was saying that he thought that the hole was actually on Columbia was in the six to 10 inches reading, based on the telemetry and the burn path, and all that. Given the what you're talking about with the flight day two drift-away object, if you had a hole six inches across, just to take the lower bound, can you get a piece of debris coming out that would be big enough to explain the flight day two object? And that's part A. Part B is, what do you think the actual hole was, or is this, you know, six to 10 versus 16 by 17? Is that all the same thing, given the error bars you guys are working on?
MR. HUBBARD: The answer to the second one is yes. I mean, I let me just give you a couple of examples, and I'll come back to the first one in a minute. The variation in freshly made RCC breaking strength is 70 percent by measurement. The variation in velocities that we could have used is as low as 650 and as high as 825 feet per second. The size of the foam block was variously estimated at 850 cubic inches to 1,600 cubic inches. The density of the foam varies from two pounds per cubic foot to 2.6 pounds per cubic foot.
So, at all of these ranges, what we picked was what the engineering and scientific community felt was the best sort of mid-range. So, we could have done a higher end test or a lower end test. We picked something in the middle. Given that range of variabilities, which is, what, about 30 percent, 70 percent, 50 percent, to me, 16-inch hole or 10-inch hole, that's all the same. I mean, it's all in the same ballpark. And we demonstrated the important thing, which was the clear connection between foam and a breach of about the approximate size.
In terms of the flight day two object, if you look at your package or you recall this maze of cracks, if the actual initial breach was smaller, I'm convinced you would have still had this maze of cracks going out, and literally, with some of these pieces just hanging there, it wouldn't have taken much, I don't think, during entry to begin to heat up and loosen, mechanical vibrations, aerodynamic forces, and create the second-day object. So, it's certainly in the range of possibility.
MS. BROWN: Todd?
MR. TODD HALVORSON: Todd Halvorson of Florida Today.
Let me see if I can figure out how to ask this. But, I was curious about the reaction that people had at the actual test on Monday. You had Board people, you had NASA people, a bunch of engineers. You shoot the foam. Big hole. There was gasps, and then it's almost like you scored the winning touchdown in the Super Bowl. And that the reaction seemed a little bit odd, just I guess just because we're looking at what kind of doomed the shuttle or what did doom the shuttle. And I was wondering if you could explain that to me, or is this something where an engineer has finally found a cause and can go off and work it, or I'm curious about the reaction.
MR. HUBBARD: I'll tell you how I felt, and then maybe comment a little bit on what I observed. But, I think it's very mixed feelings. I think you have technical people there who spent months, five months or more, including myself, trying to make that connection, trying to really understand what brought down the Orbiter in a technical sense. And so, when finally you get to the point of doing tests that is as good as you can make it, and it succeeds in making that case, then, of course, you feel briefly, like I did you know, great. You know, we found what we were looking for.
But then, in the next split second, it comes back to you why we're doing this in the first place, which is to understand why we lost seven astronauts and an Orbiter. And so then, you quickly move into an emotional reaction. So, it is with very mixed feelings that you carry out this sort of accident investigation.
MS. BROWN: Okay, Richard?
MR. RICHARD HARRIS: Richard Harris from National Public Radio.
Now that you have a clearer and I use the parameters of the hole that you're ever going to get I'd like to ask you about considering, again, looking at liftoff. Is there anything that you would have expected to see from liftoff, either some drag caused by this, pieces shedding during liftoff, any of the visual imagery? I seem to I can't remember I was trying to picture in my head what those videos were. But, would any of this have fallen into the field of view of the imagery? Is there anything liftoff that supports this, or that make that you would have expected to see and don't?
MR. HUBBARD: Well, let's see. Let me try to give you a brief answer to that. If the high-definition film camera had been working or a high-definition television camera that had a resolution equivalent to the film camera had been working, that at that distance, would have had excuse me a resolution of maybe six inches or so. As it was, the only camera that was working had a resolution, because it was normal videotape, of about two square feet. And this hole, as large as it is, is just at that limit, so all the enhancement that was done, looking from the underside of the Orbiter, didn't see anything. I've not seen anything there with that resolution. And again, of course, you're looking at black on black, so contrast is a big issue.
If you had had a camera of the resolution of, you know, from the ground, six inches or so, then you might have seen something. There are, as you will see when you go through the details of the joint scenario, a little more definition of some of the small temperature increases that were observed after the fact during the ascent, and those may be linked to temperature increase, even on ascent, of the air from the outside getting into the inside of the wing-leading edge. So, from the data that we have, nothing was seen. If there had been a camera with as high resolution as the film camera that saw it from the other side, we might have seen something as small as six inches or so, again, depending on the contrast.
MR. HARRIS: Radar there were reports of radar imagery from a little bit later in flight of objects coming off. Would you have expected to see any radar traces from this, and did you?
MR. HUBBARD: There were a lot of radar hits, none that I know of that were directly connected with this accident. They you know, they see a lot of things in the air, and radar, of course the resolution of that is not you know, it's very difficult to push the resolution of radar down into the couple of square foot size.
MS. BROWN: Okay, Matt?
MR. MATTHEW WALD: Scott Matt Wald with the New York Times.
Your analysis presents two possible recommendations to NASA. One is to double the design strength of the leading edge. The other is to be able to diagnose this in real-time and do an abort before MECO when you see a big hit to your leading edge. Is either of those a realistic possibility?
MR. HUBBARD: Or a third possibility is don't let any bipod ramps come off and hit the wing-leading edge, which I think is where NASA is headed. So, one answer is, ÒJust don't ever let this happen againÓ by eliminating the source. I believe that they are re-designing the bipod ramp to completely take out the foam. I know that there is a lot of work going on on the other foam, as well, which typically impacts the tiles. So, I would say that and there are scenarios that the astronaut crew practices of abort scenarios before orbit or engine failure. That's true.
I don't know if I would and I'm just talking here we don't have a recommendation in the work on this. But, I think that one thing that you might want to do, following along the idea that this is an experimental vehicle much more so than an operational vehicle, is to have more nearly real-time vehicle health monitoring. We have these boxes, the OEX box, the scaled down versions that are in the three surviving Orbiters, so-called MDS, Mission Data System, but those are recorded and played back afterwards. If there was some way to do a way to make some of that data available in during the mission, might give the astronauts more information about the health of the vehicle.
MS. BROWN: Okay, Bill?
I'm blinded by the light a little bit here, so you guys are going to have to help me.
MR. FRANK MORRING: It's Frank Morring with Aviation Week.
You mentioned that the break the breakage level of the panels was determined at some point. How was that determined? Have these panels been tested to failure before?
MR. HUBBARD: The material has been tested for failure, that is to say the reinforced carbon material they'll take what they call a Òcoupon,Ó they'll take a chunk, you know, like they might take a piece they manufactured that's going to become part of a panel, and that gets tested to failure in a number of different modes. One is by bending; one is by tension, by pulling it apart; one is by compression, putting it together, and so forth, and those values do exist, and that's what I was referring to was the basic material itself. There are there is much, much more limited data on testing the hardware as a system or as a whole piece. The nose cap was once tested by static loads to failure. There have been other tests of a panel like this of just pressing on it until it breaks, again, a static load. There has not, other than the few cases you might be aware of about micrometeorite debris, there has been very little or no testing of the system.
MS. BROWN: Okay, Nick, do you have a question? Anybody down here? Gwyneth? Over there?
MS. PATTY REINERT: Hi. Patty Reinert with the Houston Chronicle.
Admiral Gehman talked about toughening the Orbiter, and you've just spoken about eliminating the foam to eliminate the debris strike. What about other potential sources of a hit, and how much tougher would you have to make it? What would you have to do?
MR. HUBBARD: Well, let me talk about one thing that was done, as a historical example. There is a type of tile called TUFI tile, T-U-F-I. It is heavier than the material that covers most of the bottom of the Orbiter. That's why it's not used so extensively. But, it was deliberately created to put in the back of the Orbiter to add resistance to micrometeorite strikes.
The whole issue of space travel is, as many of you know, it comes down to mass and how much energy it takes to get to orbit. So, the creation a number of years ago of this tile, which is much more impact-resistant, also required that it be heavier, and there is some discussion now about whether or not that tile might be deployed and put in places that are sensitive, main landing gear door and closeout panels, and so forth. So, that's a historic example I can give you of where that was actually done, and I know that the engineering staff of the shuttle program is thinking about similar things.
MS. BROWN: Question over here?
MR. NICK ANDERSON: Nick Anderson with the L.A. Times.
You spoke about the maze of cracking that you detected after on the firing test on Monday. Was that very difficult to detect? I mean, was it just quite apparent when you looked at it by hand and by eye?
MR. HUBBARD: Very easy to see, and if people up in the booth there, if you can go, I think, just one slide forward from where we are, you can see those cracks there. They're very visible right after the shot. We didn't I the quick look, we didn't have time to go and measure them and count them and so forth, and that work is still going on. But, they are very apparent.
They also, in some cases, run along a region called the doubler. There is a part since panel eight is the widest one and, therefore in a sense, more susceptible to force in the middle of the panel, more flexible, what they did when they designed it was to add an extra piece of RCC, and the break where the hole is in fact, if you were to go back to I don't know if you can get there or not, but the debris hole, that is to say this one, ÒPanel Eight Breach Created By Impact Test,Ó the bottom of this while they're looking for it this runs right along the so-called doubler panel where extra strength was added. Yeah, excellent. There you are. So, the bottom of that the bottom of the hole there runs right along an area that had been strengthened. So, it broke at the weakest point.
MS. BROWN: Okay. Another question back here?
MS. KRISTY NABIELSKY: Kristy Nabielsky (sp) with N.K. (sp) newspaper.
Based on what you've told us about the day two debris event, it sounds like you're ruling out it being either a T-seal or a carrier panel, which you had thought it might be up to this point. Is that correct?
MR. HUBBARD: I don't know that I'm ruling it out. I'm just saying that this test created a very plausible piece of debris that could match one of the two or so remaining examples that I went through this morning just to be sure the report of the joint report of NASA and the Air Force Research Labs and all the things they've excluded, and it pretty much came down to a T-seal that had one of these ears on it. It needs that to reflect the radar and as it tumbles, or a piece of reinforced carbon panel, either one with a lip on it that's smaller or a bigger piece, and this impact matches that very nicely. You know, you can't say for sure by any means that a T-seal might not have been involved if you hit this somewhere slightly differently.
MS. NABIELSKY: (Inaudible).
MR. HUBBARD: I'm sorry, I couldn't hear that.
MS. NABIELSKY: You don't think a T-seal then came loose and came off, did you?
MR. HUBBARD: Well, this impact, which is the best we could do to match the accident and again, there are a lot of unknowns points more toward the RCC piece rather than the T-seal piece. But, of course, we will never know exactly where the foam hit.
MS. BROWN: Okay, Gwyneth? Over here in the second row? There you go. Stop. Back up. No, second row.
MR. HUBBARD: Hit her in the head there.
MS. GWYNETH SHAW: Gwyneth Shaw with the Orlando Sentinel.
I just wanted to follow up a little bit on what you were just talking about, the size and the shape of panel eight. Whether the test told you about whether its dynamics are kind of unique in terms of its vulnerability to a strike like this, whether a smaller panel might have been better able to resist at least a huge hole. What does this tell you about that particular size, shape and dimension?
MR. HUBBARD: Well, we'll have to hypothesize here a little bit together. I mean, I can tell you what the facts are. The facts are that this is the most unusual panel of the 22. It is the largest panel. It's also got multiple curvatures on it. Because it was designed to be the panel where this transition takes place, and you've got five, six, seven. These are fairly standard panels, about 19 inches across and about 19 inches high.
And then, you make the transition in the shape of the wing. This is not an arbitrary shape. This is exactly how the wing is configured. So, you have to make this transition from down here to out there, and you end up with an unusual panel. It's about, I think, 26 inches by 21 inches or so, so it's the largest one.
And if you think about it for a minute, you remember when you were a kid and you thought you were going to be a karate expert, and you were going to break a board, you know, and if you get your two bricks and lay your board across it, if you put the two bricks this close together and try to hit it, you'd break your hand. But, if you put the bricks three or four feet apart so you've got this board suspended between them, you can apply a lot more leverage. The lever arm, the mechanical advantage you can apply, is much greater. So, talking just in those simple terms, then, this there's you can apply more mechanical advantage in the center of this panel than you could in a more narrow panel.
Now, by how much, I haven't done the calculation. All this says that, in that sense, maybe panel eight is a little more vulnerable to a strike in the right spot. But, acknowledging that I think 25 years ago or so when they designed this, is part of why I think they put the some of these doublers in here. But, you raise a good point.
MS. BROWN: Yeah, sure, go ahead. Wait for the mike.
MS. SHAW: Could you talk a little bit more about the doublers and why where the reinforcement is exactly, and what it is in comparison to the rest of the panel?
MR. HUBBARD: Just so happens that there are two doublers. There's a lower doubler and an upper doubler, and these are located one down along here. We can get you the exact spacing, if you want, but it's maybe a third of the way to the apex along the bottom of the panel.
And then, there's an upper doubler, which is here in the upper part of that, of the face of this panel, and those are put there to add extra strength to the panel so that it would be fairly rigid and wouldn't flex a great deal when it's bolted into place.
MS. BROWN: Okay, any other questions? Okay, that's a good sign.
Thank you very much, and we'll see you again sometime soon.
MR. HUBBARD: Thank you.
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