CAIB Press Conference Transcript 8 April 2003 (Part 2)

DR. WIDNALL: Well, I’ll report a little bit on the activities of Group 3. Group 3 is basically what we sometimes call the technology group. The group is very interdisciplinary; and our role is to really bring the various engineering and technology disciplines, materials, structures, aerodynamics, chemistry, to really examine the incident itself, the early development, essentially, the loss of the vehicle.

Scott Hubbard is working on the whole issue of damage from the foam strikes. He’s coordinating the tests that will be done at Southwest Research Institute, both on testing RCC panels and testing the tiles. Just to show you what kind of fun engineers have, they have a big foam gun which is capable of shooting a very large piece of foam at a test object; and we think those tests will be very important. Scott’s putting a lot of energy into that.

Roger Tetrault is basically focusing on debris, where they’re found, what kind of damage there is, sort of a debris forensics analysis; and this is an area that’s developing really quite rapidly. The image I will carry of Roger from this experience is Roger running down the hall with a piece of paper, waving it in his arms, saying, "Look what we just found." So that situation is developing as we speak, and we are continuing to find interesting pieces.

Jim Hallock is basically doing a whole variety of things, but I could focus on he’s basically paying a lot of attention to the closeout of all the various fault trees that NASA’s working on. He is also focusing on the sensors. We get several things from the sensors. Ideally, we get truth from the sensors. We also sometimes get evidence from the sensors in the sense that if a wire to a sensor burns through, we not only know that we lost the sensor but we get information about what may be happening at another point on the vehicle. So he’s looking very closely at that and, as you can imagine, with the recovery of the OVE, he’s spending a lot of time looking at all the data bits that were obtained from that. I think, in general, it’s too early to say what conclusions are coming out of that; but it’s an extremely important process.

I am really focusing on the aerothermodynamics of this region of the flight, the re-entry. This is an extremely hostile environment, as I’m sure you all recognize. My own view of this is that this is primarily an aerodynamic heating event as opposed to an aerodynamic force event. However, the early aerodynamic forces, I believe, are a diagnostic tool because when you do have a change in aerodynamic forces due to some kind of damage, it could give you an indication of what kind of changes to the external shape of the vehicle have been produced by this heating event which we certainly believe scattered debris over several states. So that’s kind of what I’ve been focusing on.

I want to access the external configuration and sort through some of the scenarios. The first slide that I put up is an example of this. The vehicle remained in control for a very long time, up to what we sometimes refer to as loss of signal, loss of control, so that even though it was damaged and had a different shape, the control system was, in fact, able to fly the vehicle on a nominal trajectory. What that allows us to do is to back out the aerodynamic forces that were different from the aerodynamic forces on a nominal flight, and we refer to those as the off-nominal aerodynamic forces.

Now, this is a bit of a sensitive analysis; and if you actually have a situation where the vehicle is, in fact, maneuvering, then you sort of get what scientists and engineers often refer to as a zero-over-zero situation, where you have a lot of sensitivity in your analysis.

Let me talk through this analysis and sort of show you what I draw from this. First of all, we have an off-nominal roll moment and an off-nominal yaw moment. I’m a very visual person, so I wanted to locate these off-nominal aerodynamic forces on some kind of geography of where the vehicle was and try to identify not every event that took place but what were some of the key events which perhaps could have led to a change in external shape. So I was, in fact, somewhat surprised to recognize that the off-nominal forces occurred off the coast of California. What that sort of says to me is we’re not going to find that piece probably in the ocean somewhere. Maybe it will wash up, but obviously that’s very speculative.

I should also mention that it’s very important that this analysis be done accurately; and every time there’s new information, this analysis is redone. The difference between the black line and the blue line is that the group that’s doing this at NASA now has information about some upper atmospheric winds. So they have corrected their original analysis to include the effect of upper atmospheric winds. These do make difference. So we’re sort of zeroing in on the off-nominal aerodynamic forces to a degree of accuracy.

I mentioned the issue of sensitivity of the analysis. When you go through roll reversal of the vehicle, you cannot do this analysis to any degree. So don’t read anything into these fluctuations. It’s really a breakdown in the analysis. What is interesting about this is the behavior of the roll moment. This reversal of the roll moment is very intriguing, and one can postulate a number of aerodynamic scenarios. We do not have an explanation for the reversal of the rolling moment. I think we sort of understand the increased yaw moment. This could come from increased drag on the left side of the wing, but increased rolling moment can only come from increased lift on the left side and we don’t at this point understand that.

In terms of when that began, it does, in fact, correlate with a flash in debris event that was observed. I attach no particular significance to Debris 14. It was just an example of a debris event. We have the Kirtland photo which reminds us what the vehicle was telling us at that point in time and then finally the loss of control. So from my point of view, it’s telling us something about the external shape of the vehicle; and that’s a line that I’m pursuing.

Now, the next slide. Basically we do have some data from the OVE. I’m not presenting this as anything to draw a conclusion, but I want to show you the typical data that’s been recovered from the OVE and how it relates to other tests that NASA has been doing. So I was very interested in this particular one which is a temperature sensor from the left side of the OMS pod. The next slide shows what that looks like. This is a kind of nominal set of flights. This data does this. Aerodynamicists are not too surprised when things first go negative and then go positive. It could be a flow structure that’s moving.

The next slide shows how one would begin to think about that in terms of some wind tunnel tests that NASA had done. I just point to this one in particular. NASA has done a very comprehensive set of tests on models where they have removed individual RCC panels one at a time and measured forces and heat transfer.

This is interesting. It seems to correlate with the tests they did to remove RCC Panel No. 9. Again, this is not an exhaustive analysis of this. I present it more as an example of the kind of testing and correlation with data that is going on now, but you see this is a heat-sensitive paint that’s put on the model. So where you have yellow is a high temperature, and one can then begin to correlate this high temperature with the front of the OMS pod where that particular temperature sensor was located. Again, this is just an example of the kind of analysis that one has to go through to make sense of all of this.

Okay. I will think it will come as no surprise to you that we are very interested in the whole question of the RCC panels. That is starting to emerge as obviously a scenario for the accident. The next slide shows the debris from the RCC panels that we are getting. We are very interested obviously in the fact that the left RCC panels have come off before the right RCC panels. This is their location along this debris corridor.

Admiral Gehman mentioned that we’re very interested in whatever would be found west of I-45, and the search has been expand in a systematic way to go west of 45 from the point of view of the cause or scenario development of the accident itself. Obviously, I think the most interesting pieces will be found in this region; and, in fact, we are finding pieces. So that scenario will emerge.

The admiral mentioned the Littlefield tile, which up to now, I guess, has been our westernmost piece of debris. This is a rapidly changing story. I think this morning we thought it might be a black tile. Now we think it is a white tile that’s been painted black by some kind of disturbance in the flow, but I think at this point the group that’s looking at that believes that this is a tile that comes from the upper surface near the leading edge, kind of in back of RCC Panel 8, 9, that general area.

Stay tuned. That’s all I have.

ADM. GEHMAN: Left wing.

DR. WIDNALL: I should say left wing. If I don’t say it, I mean left wing.

ADM. GEHMAN: Thank you.

All right. Woody.

LT. COL. WOODYARD: Okay. We’ll begin with questions here in Houston.

A REPORTER: New York Times. You don’t have a conclusion. You have emphasized the uncertainty of what the radar signature is of the mystery object on Day 2. You were presented today with a very detailed map of damage historically to tile. I gather there is no similar map for damage to RCC from impact. You’ve ruled out SSME. You’re on the verge of ruling out other things. Can you rank what you’ve got now? You have said what it isn’t. You’ve raised the possibility of damage to RCC. Are there any other leading theories besides damage to RCC on liftoff?

ADM. GEHMAN: Yes. Any part of the leading edge system is a candidate for the intrusion of heat into the front of the wing. So T seals, horse collars, carrier panels, pieces of RCC are all candidates; and they are all in the family that’s being tested. What General Deal was saying is that you can’t prove a piece by this kind of methodology, you can only eliminate pieces. So now we’re sending up varieties, variations on the theme, a carrier panel with more tiles attached. We tested an RCC panel, a complete RCC panel. Since the debris indicates that almost all of the RCC panels fractured in the middle, now we want to know what does a half of an RCC look like for radar reflectivity because it has sharper edges. Sharper edges, tetrahedral corners is what makes radar reflectivity. So does that capture it.

GEN. DEAL: Yes, sir. Exactly. The first test — and I don’t have a chart to show you — it showed that the carrier panel that we had being tested up there, portions of it fit within the band of the radar cross-section. What we’re trying to do now is build it up to where it could have been with additional structures such as the brackets that it attaches to in the back and look at three- and four-tile configurations, as the admiral mentioned. Then as he said, the entire RCC panel did not show that it fit within that, but a partial one might, as a T seal we did not test. So we’re narrowing it down right now with radar cross-section and, again, we’re going to have to fit that back in with a ballistic coefficient, as well, as it would start to re-enter, to see if there’s a match there. So again, hopefully within the week we’ll give you more.

A REPORTER: Aviation Week. For General Deal. You mentioned that the Columbia orbiter had spent a lot more time in the pad. Are there any other ground-handling factors that distinguish Columbia? Also, is there a reason why it was in the pad longer than the others that you’ve been abled to identify?

GEN. DEAL: This is a new one that we’ve just started looking into. So unfortunately I don’t have anything conclusive to tell you yet. Part of what we are seeking is we’ve got the amount of days spent out. Now, we’re looking at what the meteorology was during that time period. So we’re going back. We are in the process of looking at that, you know, what type of rain exposure or water exposure could have been on it as well and also how much it was uncovered during that time period. So we are at the initial stages of that. Stand by for news.

A REPORTER: Washington Post. For Dr. Ride. I’m wondering, Dr. Ride, in your interviewing and putting together this storyboard that you were talking about on decision-making, have you come across anyone yet who felt that his concerns about the condition of the left wing during the mission or the need to photograph it were not listened to or given short shrift.

DR. RIDE: We’ve now interviewed, I would say, most of the engineering-level folks who were involved in the debris assessment team and basically the team that was formed immediately after it was realized that there was impact, to assess that impact. That team met as a whole on, I want to say, January 21st. It might have been January 20th that this particular meeting occurred where they believed that, coming out of this meeting, the concluding idea of the meeting was to request imagery. Then they made an attempt to go through actually a few different channels, and we’re still tracing down exactly what happened through each channel, to get the imagery taken.

They had what you can appreciate is real good engineering reasons for wanting the imagery. You know, this is a pretty complicated process that they go through. It was a large team, and it was a large team because there are several steps that are required in this. You know, the first step was just analyzing the video from the launch and determining there was something that had come off and had hit the orbiter.

So the first step was about how big is this piece. And that’s the photo folks. They give the size of the piece and location that it came from to the transport folks, who then take a look at the aerodynamic fields between the orbiter and the tank and say, okay, well, so where did this thing probably hit and at what angle. There was a fair amount of uncertainty in that. In fact, a large amount of uncertainty in that.

So their responsibility was then to pass that on. You know, it probably hit going this fast at this angle in that place, but they couldn’t pin it down and they didn’t pretend to be able to pin it down. Their job was to hand that to the impact people who would, you know, say, okay, it was coming this fast, at this angle, so it created this much damage. But they didn’t really feel that they had accurate input to make their assessment.

They would then hand off the tile damage that they calculated to the thermal people, who would calculate the potential thermal damage to the orbiter. So there was this whole string of engineers who were all in this meeting together who all said: We need to constrain this problem more. We need some more information. We need some more data. We could use some images. Let’s go request imagery.

Now the question is why didn’t that request make it to the program managers and up into the system. We think it’s a little too early to characterize all the different places where that broke down, but it’s everything from just missed communication, you know, to areas in the system that might not have appreciated the importance of the imagery, might not have appreciated what, in fact, it could give them. Just a variety of different reasons. So it turns out that this is not a simple story to be putting together, but that’s about where we are at the moment.

A REPORTER: Where was the meeting held and how many were in attendance?

DR. RIDE: It was tens of people in attendance, and it was an engineering meeting at JSC.

A REPORTER: Associated Press. I, too, wanted to ask a little bit more about the in-flight analysis of the debris hit. I know that after the accident we were told that Boeing and NASA was going to go back through and re-look at everything. Is that over with? Have they gone back and redone their whole analysis and what have they learned that they did or didn’t do right, or is that still ongoing? If you could sort of also put sort of a characterization on the in-flight analysis as a whole, whether you thought it was too fast, too anything. I don’t know who best to answer that.

ADM. GEHMAN: Actually that’s Sheila Widnall’s group to answer.

DR. RIDE: I can do parts of it, too.

ADM. GEHMAN: The board has conducted and, as has NASA, relooked at the analytical model they used to determine impact damage. Neither NASA nor the board are satisfied with the model. The model has a lot of limitations. It’s a rudimentary kind of model. It’s essentially an Excel spreadsheet with numbers that go down, and it’s not really not a computational model. It’s really just a bunch of data based on previous experience and some testing, but it is not a predictive model. You go and you look up where you are and you get this much damage. The problem here, of course, is that we’re off the scale.

A REPORTER: So could you characterize? I mean, it sounds if neither you nor NASA is satisfied with it, then obviously the analysis was bad in flight. I mean, how far do you want to go in condemning it?

ADM. GEHMAN: Well, I think I want to go as far as I did. Neither NASA nor we are satisfied that this model is good enough for what we need it for. It was all they had. The model we’re talking about is this crater model, and it was based upon both what they have observed and also testing. I mean, they actually have shot objects at tiles and measured what you get when you shoot objects at tiles; but as we are all aware and has been reported before, the largest object that they have fired at a tile is something like 1 inch by 1 inch by 3 inches long, nowhere near something that’s 9 inches by 15 inches by 20-something inches. So when you go and you look it up on the model to see where you are on this particular foam strike, you’re not even on the page. So now somebody’s got to extrapolate that. So that’s not a very satisfactory way.

In addition to that, the computer modeling, the capabilities of computers these days are such that you can do better now than you could then. So, no, nobody is satisfied with the state of the art, that we’re happy with the state of the art.

DR. RIDE: Let me add to that, if I could, just to broaden a little bit. I think it’s fair to stay that NASA and the board are re-looking at all the aspects of that in-flight analysis. So one example is that the ascent imagery has been reviewed now, using lots of sophisticated image reconstruction techniques, and we’ve been able to narrow down a little bit more where the hit actually occurred. So that’s one example of narrowing-down.

There are several things to ask about regarding the in-flight analysis. The use of the crater program is just one. It had also not been used as an in-flight decision-making tool before. That’s not what it was intended to be used for. There were also a couple of assumptions that were made that probably seemed reasonable at the time that, with tile damage, the damage wouldn’t go below the SIP, so that the bottom layer of tile would still be left. That assumption was made. Then, you know, was the thermal analysis done on the worst case places, did it cover any of the areas of the CILs. So all of these things are questions associated with the analysis and, you know, people are going back and looking at each of these steps along the way. Again, you know, our focus is really more on the process itself and what voice did the engineering group have and how were engineers and managers reacting to what they were faced with.

ADM. GEHMAN: I hate to belabor this but, but I fell into the trap of perfect hindsight. Sally reminded me of this. At the time they didn’t know the size of the foam. You see, I said it didn’t apply to a piece of foam that was this big and this wide and this thick; but at the time they didn’t know that. We know that now, and I inadvertently transferred myself in time there. So as Dr. Ride mentioned, that was one of the many unknowns at the time. I wanted to correct that before we moved on.

A REPORTER: USA Today. For Dr. Ride. Along the lines of some of the other questions, have you found anyone at NASA or among the contractors who had serious doubts about the crater analysis after it was completed.

DR. RIDE: During the flight you’re talking about. We have not talked about anyone yet — we haven’t run into anyone yet who had serious questions about the crater analysis. What we have found is that most of the people we talk to were not familiar with crater, and I think that that just reflects the fact that it was not a tool that was used in flight. It was not a decision-making tool, and it was not a tool that people were used to in this environment. So, no, we haven’t run into that.

A REPORTER: So were the people who weren’t familiar with crater, were they comfortable accepting the results of the analysis then? They didn’t question it too much?

DR. RIDE: It appears that they were fairly comfortable with the analysis. It appears that they asked good questions about what it was based on, they asked good questions, can it be extrapolated to a piece this large, and there was some work that had been done to try to verify that it could be extrapolated. For example, the engineers went back and tried to apply crater to, I think, the STS 50 hit to see whether it predicted something in the ballpark; and it appeared to. So they seemed to ask the appropriate questions in the meetings leading up to the decisions.

A REPORTER: Orlando Sentinel. For Dr. Widnall or Admiral Gehman. I understand that NASA is analyzing some globules of molten aluminum that were found in Utah. Could you talk about whether the analysis has confirmed or rejected the possibility that they are parts of the shuttle; and, if they are pieces of the shuttle, what is the significance of the find?

DR. WIDNALL: My understanding is that those are now considered not to be part of the shuttle.

ADM. GEHMAN: That’s correct.