CAIB News Conference NASA JSC 25 Feb 2003 – Part 3
QUESTION: This is for General Deal. You mentioned looking at the NASA chart with the various fault trees and fish bones. Can you give us an estimate of how many hundreds, thousands or whatever scenarios that the board is looking at?
And we’ve all seen quite a few of the scenarios heavily in the press, I suppose from us. But can you give us some examples of scenarios you’re looking at which have not appeared in the press?
DEAL: Well, I’m not sure that I can give you any examples of anything that probably hasn’t appeared in the press because I think just about everything in the world has appeared in the press.
(LAUGHTER)
Again, we are not ruling anything out. And I hate to continue to give that generic statement. That’s why we have gotten a list of everything that was on the Spacehab and we’re looking at things like that–not that we think that’s part of it, but we’re looking at it.
If I were to try to tell you that we’re focusing in on a few, that would be improper for me to do, because we’re trying to eliminate everything that is not a part of it, as we still focus in on these key indicators that Scott Hubbard has alluded to, as well as the admiral and General Hess.
There are a number of key things that you, through your questioning, have keyed on. Of course, we’re keying in on those. But that doesn’t mean that we’re eliminating anything else at this point.
So that’s a fairly generic answer. I’m sorry I can’t be more specific with you.
HUBBARD: I think it’s fair to say that we are going to track that. And as NASA works through the various elements of the fault tree and makes a determination that some element of it just couldn’t have contributed to this tragedy and they close it out, we will be looking at that and see if we agree with that or if we–and say, “Go ahead, that’s closed,” or if there is additional things that we feel need to be done.
QUESTION: Okay. But can you give us an estimate of the numbers, whether it’s hundreds or thousands of different scenarios you’re looking at? I certainly hope it isn’t . . .
HUBBARD: It’s thousands of paths through the fault tree.
QUESTION: I’ve been watching launch replays the last several days. And I have noticed that there is one piece of debris that seems to be bouncing off the left wing of the shuttle.
And I’m not talking about the pulverized foam image that we all have seen, but I’m talking about a solid, white object that seems to be just bounce off the left side. And I was wondering if you have any idea of what that might be?
GEHMAN: You want to try that, Scott?
HUBBARD: Sure. I know the video–at least I believe I do–the one you’re referring to. And we have looked at that piece that was taken from a camera observing the orbiter on ascent at 82 second period. And there are several things in there that are quite interesting.
The visual analysis sub-team working group that’s over at Johnson Space Center is going through this meticulously. We have stepped through it. In fact, I asked for a special viewing of that, stepping through it frame by frame.
The initial piece of debris, which appears to be a single element, appears. There is what we think is an optical illusion that it appears to actually go up. This may be due to the angle at which you’re looking at it.
It’s actually coming out and away. But because of the angle, it looks like it’s rising, which would be a little counterintuitive.
Then the three pieces or so appear. And at that point, even if you step through it frame by frame, it’s a little difficult to determine exactly what happens next. Those elements disappear. The objects disappear.
And then you see a plume. You see an object, apparently at the bottom of the wing. And then you see more of the debris crossing across the bottom of the solid rocket motor.
I don’t draw any conclusions from this yet, except to say that this is a fruitful area for further enhancement by the video experts. And they’re working on it and are going to get back to us when they have reached the next stage of sophistication.
QUESTION: This seems to be moving to the right on the screen. I mean, it just bounces and then moves to the right.
HUBBARD: There is an element that appears to do that. What I’m trying to emphasize is that I think we’ve already seen one optical illusion because of the angle at which we view this. So I am reserving judgment on which direction it went and whether it hit something or not until we go a little further.
QUESTION: For Brigadier General Deal, how close has Space Command placed the object to the shuttle on flight day two?
DEAL: Well, I can’t give you an exact number of feet. It was floating near the space shuttle. And again, I’ll go back to the laborious effort that’s taken place, trying to detect what happened to this particular object.
It was floating nearby is when they detected it. And I don’t have the exact number of meters there, but far enough away so they could tell it was a separate object.
But again, this is in what we call the scan mode. And it’s not unlike a ground-based radar that’s looking at a scan. And then it may lock in, like a fighter aircraft radar, lock in on a specific target.
They weren’t doing that. They were doing a regular scan of everything crossing the horizon in their normal, everyday, day-to-day mission, 24-hour-a-day mission, looking for missile warning and for low altitude space tracking. So they were observing it come overhead.
And then, as they went back and did the delog I was talking about, again in a scan–not what we call a pencil beam where they’ll send a pencil beam-sized burst up to look and identify what it is–they identified it slowly starting to fade away. And it was from four different worldwide sites that were able to see this as it floated away. Had sites in Eglin Air Force Base in Florida, Beale Air Force Base in California, Cape Cod Air Force Station in Massachusetts. And there is a system called the Navy Fence that’s at several locations across the United States that looks.
So they all saw this small piece of debris that appeared to be accompanying the shuttle and separate from it. So it went from very close to a standard degrade of an orbit as it separated from the shuttle and did what most low-Earth orbit objects will do. And it degraded three days later and came back into the atmosphere.
QUESTION: I’d like to explain to my editors what’s a fault tree and what’s a decision tree. Can you gentlemen help me, please?
GEHMAN: A fault tree is a tool for making sure that you have a visual representation of all the possible causes of an anomaly. And essentially what you do is you draw a diagram that allows you to account for every possible thing that could go wrong. And you keep breaking it down into more levels of detail and more levels of detail until it looks like either the roots of a tree or the branches of a tree, depending on which way you draw it.
And it’s an analysis tool. It’s normally used as an analysis tool for fixing something which breaks. It’s not specifically designed for a catastrophe like this.
But there is a fault tree for every part of the STS system, more or less sophisticated and more or less complete. And so it’s useful if you think that some part of the orbiter or some part of the system broke to go to the fault tree and start using it as a road map so you don’t overlook anything.
That’s the best I can explain it.
QUESTION: A question for Scott Hubbard on the–the assumptions you were telling us about in your opening remarks about an area that you assume is damaged and then you can model and get plume that explains what you might have been seeing in the wheel well.
And then you mentioned again some sensor data up on top. My questions are: where exactly was your presumed area of damage? I’m trying to get a sense. Did that actually cross a landing gear door hinge line or the seal area? Was it in front of it? And you’re assuming plume got in.
Can you give me some specifics? And also, when you mentioned above the wing, I’ve been fascinated from day one about the data from the longeron sill area, which is well above the wing, and other side wall sensors. Is there any sense of what’s going on there to explain that stuff?
HUBBARD: Okay, let’s take the first one first, Bill. Let me go back and make sure the point I was trying to make is clear. What the NASA Mishap Response Team engineers have done is an initial set of thermal calculations.
What they were trying to explain was the very rapid 60 degrees in five minutes temperature rise in the wheel well area. And to do that, they started off with a fairly straightforward and simple set of assumptions. This is what you always want to do if you’re trying to box in and go from the town to the ballpark to the seat.
They said, “Let’s just put heat on the outside of this box, this wheel well.” And they raised the temperature and increased the heat to what is known about the environment. And they could not reach the kind of temperatures inside the wheel well that were measured.
So they said, “Well, let’s imagine then that we have a breach somewhere. And that breach was not specified. It just was a breach of 20 square inches–you know, a hole four inch by five inch–somewhere and you just dump this heat into the box.” If you do that, you can, in a simple calculation, show the temperature would rise to the observed level.
That’s about as far as they had gone a day or two ago. What they need to do next is exactly what Bill Harwood is asking about, which is a much more sophisticated analysis of moving this breach around, dealing with the structure on the inside, which is very complicated.
You’ve got bars. You’ve got various apertures. You’ve got structure.
And once this superheated air would get in there and try to move around, you’re faced with a much more complicated area, which is the area of computational fluid dynamics. It’s not impossible to calculate this. In fact, there are people that have done that for a living for decades. But it’s going to take a while to get to the next level of sophistication that we would all like to see.
The second thing has to do with where the sensors are and what kind of data we’ve seen. And the team is in the process of providing the board with data that is in three dimensions, not just two, so that we can stand off and see where the sensors went up in temperature, not just looking down at it from a top-eye view, but looking from the side and then stepping through that in time sequence.
And I think when they finish that analysis and we can make it available, we’ll be able to address some of the questions about upper versus lower.
QUESTION: My question is sort of generic.
I covered the Challenger accident. And I covered the Apollo fire. So I’ve been around during several accident investigations. And there has never been complete agreement among the panel. I’m thinking specifically about the Rogers Commission.
Have you considered what, if you do not agree with each other 100 percent, what you are going to do then?
GEHMAN: Yes, we have. And it hasn’t come up yet. But if someone feels strongly that they need to in some way express their opinions different from where the report reads, then we will have a minority report attached to it.
QUESTION: For General Deal, you talked about the approximately one foot by one foot piece of debris that was tracked after the second day of the flight. You said it was lightweight.
Is it consistent then with what would be a space shuttle tile material? And is it consistent with something that could have been knocked loose by a hit of orbital debris?
