Report of the PRESIDENTIAL COMMISSION on the Space Shuttle Challenger Accident

 

Volume 4 Index

 

Hearings of the Presidential Commission on the Space Shuttle Challenger Accident: February 6, 1986 to February 25, 1986

 

Note:
Centered number = Hearing page
[bold number] = Text page.


[495] 919

 

TESTIMONY OF JACK LEE, DEPUTY DIRECTOR, MARSHALL SPACE FLIGHT CENTER, AND HEAD, MARSHALL CONTINGENCY INVESTIGATIVE TEAM

 

 

MR. LEE: I am Jack Lee. I am Deputy Director of the Marshall Space Flight Center, Bill Lucas' deputy, and the day of the incident I was assigned by him to head the Marshall contingency investigative team for the elements for which the Marshall Space Flight Center is responsible.

(Viewgraph. ) [Ref. 2/13-28]

MR. LEE: We want to cover two subjects today. I would like to give you a brief summary of our contingency team activities, and more specifically, what you have been waiting for is a status report on our failure analysis.

Could I have the next chart, please?

[496] (Viewgraph. ) [Ref. 2/13-29]

MR. LEE: We are operating under a contingency plan which was approved prior to the 51-L flight by Bill Lucas. It consists of working groups for the inertial upper stage, the external tank, the Shuttle main engine, the solid rocket booster, the solid rocket motor, and for this particular activity we established a systems team because a number of these elements come together. Our team is comprised of both NASA and the contractor personnel. We located these people in the Huntsville

 

920

 

Operations Support Center at Marshall Space Flight Center, and we have impounded the data as directed by Jesse Moore, and we have maintained the impoundment of this data with the possible exception of in some areas we have to take film out for special analysis or some data for special analysis, but it is under our control, and we have a secure area at HOSC.

The areas we chose to review, as they were directed by the contingency plan, is the entire manufacturing process, manufacturing and processing for each of these elements, the acceptance test packages. That is, in the case of a Shuttle main engine, that would be not only the static testing but the factory checkout from the time it leaves the factory until it goes through the prelaunch processing here at the Cape.

In the case of the solid rocket boosters and the used cases of the solid rocket motor, that would include the refurbishment and reprocessing of each of those, and that is acceptance and transportation. We include the transportation from the manufacturing site to the test site and to KSC. Specifically what we are looking for here is any unusual environments which the hardware goes through, usually humidity environmental, accelerations and so forth.

We have reviewed the data packages for the

 

921

 

prelaunch activities here at the Cape and the actual flight data. Now, within those reviews, the status of those reviews, we vary from 75 to 100 percent of that activity. Thus far we have looked at all of that data. That does not mean we have completed the analysis and stopped looking at that data. That means that one of our teams has looked at that from at least 75 to 100 percent of them.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-30]

MR. LEE: This is a graphical time line.

MR. SUTTER: Excuse me. You are doing this test and analysis?

MR. LEE: No, no, no, this a review of past history of this hardware. Now, what we are doing in relationship to the failure analysis, we have another presentation to go into detail on that, but this is a category review, if you will. We have looked back to see if there were any configuration changes or anomalies or problem reports in the history of this hardware that have been identified which could contribute in any way, either directly or indirectly, to this.

DR. COVERT: Does this also include the catalogue of waivers?

MR. LEE: Everything.

 

922

 

MR. SUTTER: There have been a lot of design changes.

MR. LEE: No, there haven't been a lot of design changes.

MR. SUTTER: In my opinion there have been.

MR. LEE: Not on this vehicle.

[497] MR. SUTTER: There have been a lot of design changes from the first one to this one, and this one is the last one that had all of them.

How do you go back and look at that as you progressively put them in, and one of them may have tripped an incident.

MR. LEE: Let me clarify. I did not explain properly. This is the deviations from the previous, from previous vehicles. In other words, we are looking at changes specifically to this vehicle and anomalies against this vehicle from previous flights, and we did not go back at this time to the first Shuttle flight. I misrepresented that if that is what you understood.

MR. SUTTER: Well, maybe you are going to talk about this, but one of the things I think is necessary is to look at all of these changes, and yes, the last flight was successful and this one wasn't, but just looking at what happened between this one and this one, maybe it was one of these other changes that because

 

923

 

something wasn't critical on this flight you got by with it, but when you add them all together on this flight, one of those other things may have tripped it over the edge.

MR. LEE: And we intend to progress progressively further back into the review. When we get to - this is our first blush at all of those elements. As we hone in on a particular like the solid rocket motor, like the external tank that we talked about, we will in fact do that, and we are doing that part of it. If in the case of - -

MR. SUTTER: Including waivers and including things that were suggested as waivers and didn't get up to design review board, and including changes that were suggested and were passed over?

MR. LEE: That's right. We will do that for sure on the suspect elements, and the thing I have reported here is we have only gone to the deltas from the last flight. We will progress back into that, yes, sir.

Does that answer that?

MR. SUTTER: Well, I think at least some members of the Commission, I think, would like to somehow review that whole history and review the actions you have taken on waivers, and how it was concluded

 

924

 

that, for instance, taking the loads on the main tank went down, why was it concluded that the initial design was one way and then somebody thought that he could change the design criteria? Those are some of the things that I think some of us, to do a thorough analysis of everything that has happened, some of us would like to go right back to that.

CHAIRMAN ROGERS: Could I just say that we are looking for a way of setting up subcommittees, and it just occurred to me how to establish one. You are the chairman of that subcommittee.

Who else would you like to have working with you on this aspect? I mean, it should probably be only two people.

MR. SUTTER: Anybody that wants to volunteer. I have got some ideas of guys that could help. Maybe we ought to have a separate meeting on that.

CHAIRMAN ROGERS: Anyway, well, you chair the subcommittee, and I think that is a perfect thing for you to do.

MR. LEE: Our configuration, control, identification, and our problem reporting system will allow us to track that, but we will probably have that in our files.

What I would like to do here is show

 

[498] 925

 

graphically a time line that we talked about that at least two of the other presenters have talked about, and the reason for the underlining in red - and this is a preliminary time line, it was as of - when I made the chart it was on Monday. There have been slight adjustments. There is only, I believe there is less than around a tenth of a second off. The sequence is right, but those times need to be adjusted.

And for my presentation purposes, that tenth of a second is not critical at this time.

Let me start with we ignited the SMSEs at T minus 6.6 seconds, as planned. T zero is the SRB ignition and lift-off. The first instant we report - and by the way, I am reporting what is predicted and was planned in some cases, and some not necessarily anomalies but some things that might be slightly off nominal, and some items that are actually anomalous by our interpretation, and I will distinguish those for you.

The famous black smoke that we just discussed, we see that first indication about a half a second, and we think we see it up until about 12, a little over 12, between 12 and 13 seconds.

I would like to add one other piece of information that didn't come out in the previous

 

926

 

analysis of that smoke. It is not all black. There is some white smoke in it, too. Just for clarity and for information about this particular column of smoke, it is very essential to us that we understand the location and the time of that smoke, and the camera angles that you have seen are not adequate to be able to produce that for us yet. We are going through some gas dynamics calculations to be able to try to relate that to the vehicle motion so that we can pin that time down exactly.

At about 5 to 9 seconds, we did see a slightly high performance on the right hand solid rocket motor. This was well within our experience base, and we don't indicate that as an anomaly, but because it changed, shifted our Shuttle main engine thrust bucket, where we go from 100 to 104 percent down to 65 percent and back up to 104 percent again, it shifted it slightly, so we went from 104 to 94 because of this higher performance here, which is still well within our experience base.

DR. COVERT: What does that say, 26 or 2 Gs or what?

MR. LEE: This is 2 sigma high performance. That is equivalent to about 18 psi, 17 to 18 psi.

DR. COVERT: 2 sigma is five times in 100?

MR. LEE: It is about three percent off of 100.

 

927

 

DR. COVERT: I'm talking about statistically 2 sigma being about five times in 100?

MR. LEE: Yes.

GENERAL KUTYNA: What could cause something like that?

MR. LEE: That is just the way the sample that we - the test fire sample of the actual grain, the five inch motor, and its performance is comparable to this. It will be a slight, not a defect, a flaw or a crack in the propellant would give you an increased irregular grain rate for a longer period of time. It is just an irregular shaping of the grain maybe, nothing - I mean, not anything abnormal about that at all from our experience base. The only reason I put it up there is to explain the Shuttle main engine throttling and because we were looking for everything that could be slightly unusual.

At 40 seconds we see a 2 degree gimbal angle on the - on both the solid rocket boosters. This is well within our experience base, and we explain that because of winds, it is directly related to some winds. We don't see anything unusual, so we don't worry about that.

[499] The first incidence that we see of an intermittent hot gas emanating from the right hand solid

 

928

 

rocket motor is about a little over 58 seconds. When we see it continuous, it is about 100 milliseconds after that. So from intermittent to continuous, and continuous is throughout the flight, this corresponds very closely to the reconstructed Max Q time.

MR. FEYNMAN: This observation is the photographs?

MR. LEE: These were observations of the photographs. These are Max Q reconstructed.

DR. COVERT: I want to go back to that earlier point, please. You sort of gave me a nice warm feeling about this 2 sigma business. You have fired 50 of these things in flight, 25 flights, I believe, and you probably have fired another dozen or so at Thiokol and in the qualification testing and so forth, so that 5 percent is 5 out of 100. So we are talking about a possibility of one failure, having one rocket having this degree of exceedance from normal, and I guess that wouldn't give me a warm feeling under the circumstances.

MR. LEE: This is 2 sigma of performance around the main performance for that time.

DR. COVERT: I understand exactly what that means, and what I am saying is if I take 2 sigma as being a variance that occurs at some degree of

 

929

 

confidence, five times out of 100, or which is one time in 20, you take the total firings you have faced, you haven't had very many exceedances of 2 sigma.

MR. FEYNMAN: Well, he has presented the data. He has told you what it is. It is 2 sigma, and it is up to you to interpret whether you think the 2 sigma is significant or not.

DR. COVERT: Okay, fine. Press on.

MR. LEE: It is in our experience. That's all I can say. It is within our experience base.

Now, the next event we see is the right hand - and this is just after we see the continuous flow from the right hand solid rocket motor, we see a divergence of the chamber pressure from the mean, from the mean of previous flights and also from the left hand solid rocket motor, and so you kind of expect that with the flow, the hot gas flow coming out of the side of the SRB.

The next event we see is the evidence of impingement of that hot gas on the LH2, the liquid hydrogen tank.

MR. FEYNMAN: Evident through pictures?

MR. LEE: Yes. That is still photographs. In this period of time we have a 2 degree per second body motion or body rate on the SRBs that we don't totally

 

930

 

understand. We have some wind sheers and some loading that we can get from what we anticipate this thrust to be. We don't have that completely reconstructed, and so I will have to say that we see this on our instrumentation, but we don't totally explain that.

GENERAL KUTYNA: Jack, let's go back to Max Q. At Max Q we have the max stress on this particular joint that we think failed.

MR. LEE: We have the maximum stress of any field joint in flight, on this particular aft joint at Max Q.

GENERAL KUTYNA: So it happens on that joint at Max Q.

Now, how sharp do we come to Max Q? Does it just happen at 58.83 or does it build up?

MR. LEE: It builds up. It could be two or three seconds.

GENERAL KUTYNA: So, at Max Q, the effect on that joint could have happened before the hot gas flows out?

[500] MR. LEE: I would say yes, and the guys who reconstructed this would probably agree with

MR. RUMMEL: How does the stress on the load on the joint at Max Q compare to the so-called tang load in the second joints?

 

931

 

MR. LEE: The bending load at lift-off, at the tang load, is high. I think it is - I believe - do you know, George, exactly?

MR. HARDY: I don't know the numbers.

MR. LEE: We will get that for you. It is higher. I know that. It is higher at lift-off.

The next event that we see is the first evidence of the liquid hydrogen tank leaking, and you would expect that from the impingement of the hot gas from the solid rocket motor.

MR. FEYNMAN: That evidence was not photo, that was pressure gauge?

MR. LEE: No, that is still photo evidence.

Now, the next one is pressure gauge evidence. The pressure transducers in the liquid hydrogen tank - there are three of these - at 67 seconds we see a decrease, a decrease in the rate of increase, which does not say that we are decreasing the LH pressure; we are decreasing the rate of increase.

DR. WALKER: And that is anomalous?

MR. LEE: That's anomalous.

MR. HOTZ: Could you just go back one event on the first evidence of the hydrogen tank leak? Where physically in the tank does that evidence occur?

MR. LEE: It is in the same vicinity that you saw the plume come out here.

 

932

 

All right, the next thing we see is another measured event on the liquid hydrogen pressure at about 72 seconds, and we differ a few milliseconds. That has to be adjusted, but at this time we see a decrease in the hydrogen tank, in the ullage of the hydrogen tank, and we are trying to make that up with the pressure, but we are not able to. So we know that the two flow control valves that feed the pressure into the hydrogen tank are in fact full open. and they are trying to make up that ullage.

MR. FEYNMAN: It is leaking out faster than the gas is going in?

MR. LEE: That's right. It's leaking out faster than the gas is going in. At the same time period we see an unusual occurrence of the right hand, what appears to be the right hand solid rocket booster, the base, what appears to be at the base coming out, okay. So like it is pivoting about the top, and it is in fact rotating relative, at an angle relative to the rest of the stack. And we compare that data with what is happening in the orbiter and the other SRB.

MR. FEYNMAN: And you have gyros in each instrument that are different from each other?

MR. LEE: That's right, and the way we would explain that would be that base rotating out. In the

 

933

 

same time period we get a lot of high rate actuator commands between, say, a little after 72 seconds up to about 72 1/2 seconds, and those are not all tied together and explained. We think we have come detached at the base, and then -

MR. FEYNMAN: The actuators are the gadgets that turn the elevons, is that correct?

MR. LEE: The actuators are the hydraulic pistons, if you will, that gimbal the engine.

MR. FEYNMAN: Okay.

[501] MR. LEE: At about 73 seconds we then see a very distinct anomaly in the right hand solid rocket motor chamber pressure, and we are seeing about a 20 psi loss in chamber pressure there at around about 600 psi, and so we are seeing a definite anomaly in the right hand solid rocket motor.

So then the terminal events are a little suspect still. We are using some film data, as you have seen, and some instrumentation, and we put just for reference purposes a time out where we saw the right hand solid rocket booster nose cap separate.

Could I have the next viewgraph, please?

DR. WALKER: Could I ask a question, please? Do you have separate measurements of the ullage in each

 

934

 

of the Shuttle main engines, or is that a single measurement of total feed?

MR. LEE: We have tied to each engine an ullage pressure measurements which allows what we call a flow control valve to divert in this case gaseous hydrogen to go back into the hydrogen tank to pressurize it, if you will, and each of these engines has two flow control valves. In other words, two of these become flow control valves.

DR. WALKER: So all three of them are shown?

MR. LEE: Yes.

(Viewgraph. ) [Ref. 2/13-31]

MR. LEE: The way we proceeded at Marshall for investigation is we start with the end item as we see it and work back to build a fault tree, and our end item was the explosion, and we tied that to a rupture or a breakup of both the liquid hydrogen and liquid oxygen tank. We built a fault tree, and this is just the overall major fault tree. There are probably 200 or 300 different elements. If I spread the whole thing out, it would be 200 or 300 elements that make this up.

Just to identify how we construct this, one area would be, to break up the external tank, would be the external tank and the solid rocket booster attach fittings fail. One would be overload of the tank or

 

935

 

load exceedance, and that could come from a number of things, control, winds, thrust imbalance. The Shuttle main engine structural failure could cause an external tank rupture. Overheating of the external tank could cause it. The external tank flaw, that would be a manufacturing flaw, or some external damage, some flaw in the manufacturing. A premature detonation of the linear shaped charge would give you a rupture of the external tank. A premature ignition of the inertial upper stage that is in the payload bay - -

DR. WALKER: Where is the linear shaped charge?

MR. LEE: That is on the external tank, as well as the solid rocket booster, here and here and comes down to about here on each of these, and then down the inside.

DR. WALKER: That is the destruct?

MR. LEE: Yes.

MR. ACHESON: Which one do you mean in that box?

MR. LEE: I mean all of them. Another would be, say, an explosion or a fire in the payload bay. Another would be damage at lift-off or premature separation of the solid rocket booster.

Now, what we have still all of these open,

 

936

 

there are two that we have close to exonerated, but we are not yet able to we are not allowed to, from the flight data that we have reviewed would be the Shuttle main engine, and we have good [502] evidence that the Shuttle main engine performed just as prescribed. We actually have data after what you see as the explosion, because we are getting our data at - our 60 kilobit data that we got longer than we did the 128 kilobit information, plus the photography that we saw. And so actually, the engine was actually still running at the time of the explosion because the feed line propellant and the fact that we got data longer, we went to the point of actually, because of the overheating or the high temperature indication on one of the turbopumps, which is a red line that would cause you to cut that engine off, and we think we can see that in the data. We actually went through the process of hitting a red line and cutting the engine on after, pretty much after.

So based upon everything we have seen from flight data and photography, we do not see any connection, any connection whatsoever between the Shuttle main engine and this incident.

We believe we can almost exonerate the inertial upper stage also. We do not have flight instrumentation of that during the ascent phase because

 

937

 

we don't need it, I guess, but it is in the bay, and we don't have instrumentation on it. We have enough orbiter instrumentation and enough payload instrumentation to be able to see in detail what is happening to that structure. We are able to look at temperature measurements. So we are reasonably sure the solids didn't fire. Everything we have looked at compares very favorably or exactly almost with the previous flight we had with the IUS, so we believe we can - we know that we can't tie the information we see today to that.

GENERAL KUTYNA: For the record, I would like to say that's the first nice thing NASA has said about the IUS in the last four years.

(Laughter. )

MR. LEE: Now, what we are leaving open with all of this - and there is a lot of it - is what happened, what could have happened with the solid rocket booster and the external tank. So we haven't tried to close out any of the external tank or solid rocket booster items. Where we will be taking off from today and in the next presentation will be the solid rocket motor failure and then some of the things associated with all aspects of the external tank.

For this, I would like to now go into the

 

938

 

presentation that we have been trying to - the group here has been trying to discuss, and I am not criticizing you for that, but we have discussed a lot of items already that we are going to tell you about now. But this is the way we see at least two very probable failure scenarios, how we went about arriving at the scenarios, the processes that we go through for identifying the trails, if you will, how we go about doing the analysis and tests, and we are going to provide to you today what we have completed and the results of what we have completed and the analysis and tests and give you an indication of the type of tests that we presently have planned.

With that I would like to introduce George Hardy who acts as my alternate for the investigating effort at the Marshall Space Flight Center.

MR. CRIPPEN: Jack, while George is getting up, just a little bit further on the IUS.

So we have recovered portions of the IUS, and that includes chunks of solid fuel that show no signs of ignition.

 

 


[Please note that some of the titles to the references listed below do not appear in the original text. Titles are included to identify and clarify the linked references - Chris Gamble, html editor]
[
503] [Ref. 2/13-29] STATUS REPORT TO 51-L DATA & DESIGN ANALYSIS TASK FORCE. [Ref. 2/13-30] SUMMARY OF MSFC CONTINGENCY TEAM ACTIVITIES.

[504] [Ref. 2/13-30] [Marshall Space Flight Center - STS 51-L TIMELINE PRELIMINARY; From: T.J. Lee; Date: February 11, 1986]

[505] [Ref. 2/13-31] FAILURE TREE.


 

[506] 939

 

TESTIMONY OF MR. GEORGE HARDY

 

MR. HARDY: Mr. Chairman, members of the Commission, I would like to discuss with you some of the failure analysis work that we are doing under the purview of the task force.

Could I have the first chart, please?

(Viewgraph. ) [Ref. 2/13-32]

MR. HARDY: I will discuss some of the failure scenarios, potential failure mechanisms or causes that set those scenarios, and then work in progress, which work in progress is a continuation of the development of the scenarios, particularly that has to do with the analysis and test work.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-33]

MR. HARDY: Just as a summary, the approach that we have taken is I think somewhat classical. It is not unique, develop failure scenario assessment matrix with that. That means to establish event one, event two, event three, etc., and with data that is in hand, the observations, film data, telemetry data from 51-L, special analyses that are run as well as tests, and our experience base. This matrix approach, then, takes each one of those events and attempts to either support it or refute it.

 

940

 

Now, in many cases, as I mentioned, that does take a special analysis and test, and in some cases we have run some of those tests and analyses, and in many cases we are still in the process, and I will try to describe that to you as we go through. But successfully completing that first step, one comes to the most probable failure scenario.

I am not prepared today to tell you which that is. I am just describing the process.

The next step, of course, is define failure mechanisms and causes. If you can make the scenario fit, something still has to cause that, and there we look at again the 51-L hardware pedigree, anything in the manufacturing of the hardware, the handling of the hardware, any design changes that might have been made. We look at our experience base, if there are any clues there, the actual design itself, all the way back to the initial qualification of that design, and then experience base, by the way, that would look at previous loads that we have exposed to various elements, compare that with our design qualification load base.

We look at launch processing, launch flight, and again, in most cases have to generate special analysis or special tests to either verify or refute a particular cause. And then, of course, if one has done

 

941

 

that successfully, you get to the most probable failure mechanism.

Now, I am going to talk to you about this and some of the work that is going on right here.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-34]

MR. HARDY: Before I get into the details of the failure scenarios, with respect to the propulsion elements of the booster, we have identified three failure scenarios, defined as first event.

The first one is an external tank hydrogen leak. The second one is a solid rocket booster joint leak, and an unanticipated vehicle loads and dynamics.

[507] There has been a lot of discussion here today about lift-off loads, the effect of lift-off loads on the attached structure, the effect of loads at Max Q, and I can assure you that we are vitally interested in that. And at this point in time, since much of that has to be reconstructed, I have not developed a detailed scenario that uses these vehicle loads and dynamics as the first event or the first offender. But we plan to do that as that data becomes available.

Now, I would also hasten to say that one can get into permutations and combinations of these failure scenarios. We are quite aware of the fact that there

 

942

 

comes a point in time, about 60 seconds in flight, where indeed the aft joint of the solid rocket motor is leaking. I think that is undeniable. The question is is that the cause or the effect.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-35]

CHAIRMAN ROGERS: Does D include on that chart the third one, the unanticipated vehicle loads, does that include the launch problems, or is that a separate category?

MR. HARDY: No, sir, that would include, even include prelaunch activities.

CHAIRMAN ROGERS: I see.

MR. HARDY: If there was some procedural error in making the attached struts or temperature conditions, the temperature around this motor case, as I will show you later, is about a 22 degree profile from the inside to the outside, and so it would include temperature conditions. It would include the effect of ice on the launch pad, if that had any significance.

CHAIRMAN ROGERS: I see. That clarifies it, thank you.

MR. HARDY: And just one other thing I would mention, too, that goes significantly into the dynamics at lift-off. We have heard mention about the bending

 

943

 

over of the booster, but it is also cantilever dynamics of the lift-off, with the simultaneity of release of the booster from the launch pad. I don't know if that has been explained to you or not, but on each booster there are what we call four hold-down posts, a total of eight, and those are released about a three and a half inch explosive bolt, or rather it has an explosive nut on it, but it has a three and a half inch bolt with an explosive nut on each one, and they are released simultaneously, they are fired simultaneous with the ignition of the solid rocket motors, and so we will be looking at the timing, for instance, of the release mechanisms themselves, anything that can put unanticipated, unexpected dynamics into the vehicle.

But as I mentioned, the detailed development of this scenario has to follow the generation of that data, and it has to be reconstructed. So I am going to be talking in more detail about these two. But we certainly will be working this one. And again, this scenario can interplay with either one of those.

What I would like first to do is to discuss just the overall scenario, the events associated with Scenario A, which is external tank leak, and then I am going to take each one of these events and tell you what we have in 51-L observed data, or what we have in

 

944

 

analysis to date, what we have in test to date, that either supports or refutes any of these steps, and I will also tell you what we have yet to do.

In the process, if you fail to refute any of these blocks, then that chain has to stay open. At any point in time you can deny one of these things happening and then you block that scenario right there, and that part of the scenario is ended. If, of course, you block it back here, then the entire scenario is ended, but this scenario has again, let me emphasize, and I am talking events [508] that occur at this point, not necessarily causes, not necessarily why they happened, but it has an external tank leaking at or near lift-off.

Let me go now if I could to the next block, and so I can talk in more detail on each one, could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-36]

MR. HARDY: I am going to address now the external tank hydrogen leaks and this hydrogen burns. When this hydrogen burns, it overheats the aft joint on the solid rocket motor, and the O-ring seals become heated to the point that they can no longer hold the pressure. They fail.

And then we go to the next step which is impingement on the aft struts and the external tank and that starts a major event.

 

945

 

Now, I am not carrying on beyond the major event. I am just trying to get to that point, and I will go through each one in detail, but I thought it would be better just to talk about them one at a time first. An alternative to the hydrogen leaking and burning is if the hydrogen leaks, it doesn't burn but it cools the joint to the point that the O-rings get so cold that the structural integrity of the O-rings is affected, and they break loose, they can't hold the pressure anymore, at which time the joint starts leaking, and I get on to this next step.

MR. RUMMEL: Excuse me. Why wouldn't it burn?

MR. HARDY: Well, I think some of it will burn, but it may not all be consumed?

MR. RUMMEL: In other words, it might burn but not impinge?

MR. HARDY: That is correct, or the flame front may be - the flame propagation may not be through all the hydrogen. It may be concentrated to the point that there's not enough oxygen there for it to burn.

DR. WALKER: Could we just return to these infrared images from which temperatures are derived, and the possibly anomalously low temperature on the right hand solid motor? Are you going to talk about that?

 

946

 

MR. HARDY: I will touch on that, yes.

Just again, let me just show you the general timeframe I am talking about these events happening. I am not really trying to tie them all down, but this first, as I say, it happens at or near lift-off. This is occurring from lift-off to about 58 seconds. This occurs at around 58.3 seconds, and that is an observation from the film. And then this also is an observation from the film.

Okay, looking at Event A-1 there, it overheats the right hand half of the field joint. The observation is that we have this anomalous smoke, we have at or near lift-off, and this could be -I am not saying it is, but it could be external tank TPS burning. So at this time - -

DR. COVERT: That TPS is the insulation?

MR. HARDY: Yes. At this point in time that observation would not deny this scenario. I am not saying that is what happened, but it wouldn't allow us to block this scenario.

So the analysis, some of the analysis we have done Dr. Lucas already mentioned. We asked ourselves, well, how much hydrogen could I be leaking and not detect it in the flight instrumentation of the tank, and the analysis says we could be leaking 4 pounds per

 

947

 

second out of a hole of eight-tenths an inch, and it would not be detected with instrumentation.

The next step was to, can I structurally survive an eight-tenth inch hole, and the answer to that was yes, it was considerably greater in the area of interest than eight-tenths inch. So I can [509] leak hydrogen and not detect it with instrumentation. I can have a hole of the size that would be undetectable in instrumentation, and it is structurally sound, the vehicle still is structurally sound, the tank is.

Now one of the thing that we are trying to do - and I am not an expert in this area, but is through film enhancement, to attempt to see if there is evidence of hydrogen, either free hydrogen or burning hydrogen in the area of interest any time from lift-off through the major event.

DR. COVERT: George, what kind of pressure difference would there be between the hydrogen tank and the outside from the insulation?

MR. HARDY: I don't know the answer to that.

DR. COVERT: Have you guys done any experiments with that pressure difference, that the hydrogen would work its way through the insulation?

MR. HARDY: I don't have the answer to that. I feel confident it would because the head of hydrogen

 

948

 

you have got there, I think that is right.

Now, at this point in time we can't block this scenario because we have found nothing in tests or analysis to date that says that at this point in time that that can't happen. So we go to the next step, and we say, well, okay, so what if it is happening, can you overheat the joint?

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-37]

MR. HARDY: This is event A-3, assuming that everything in front of it can happen and maybe did happen, and this addresses the fact or makes the statement in the scenario that the joint is overheated to the point that the O-rings fail.

Well, certainly the observation of the fact that we have a blowing leak at the right hand field joint in the timeframe of interest here that of course would not deny it. The fact that we have chamber pressure diverging would not deny that. And the fact that we have some excursion in the control system would not deny it.

The analysis that we have under way - and we have some preliminary results from these analyses, but we are refining them at this time - the question is can you get a heating rate to get the temperature of that

 

949

 

joint high enough in the 58 seconds that you have available, that is, from near lift-off to the time you see the joint leaking, can you have a heating rate high enough to overheat the O-rings to the point that they would fail? We have not concluded that analysis. A preliminary assessment of that indicated that we would heat that joint to - can you give me the number on that, Rick?

MR. REINARTZ: About 450 degrees.

DR. WALKER: Fahrenheit?

MR. HARDY: We would heat that joint to about 450 degrees fahrenheit. Now, that is assuming a perfect mixture of hydrogen with the oxygen available, that is burning, and that heat is flowing over to this joint and is being added to the aerodynamic heating that is already there.

Our preliminary assessment is that the O-rings, heated externally, would have to be heated to somewhere in the neighborhood of 500 to 600 degrees before they lost structural integrity.

Now, we haven't made a fit of that element of the scenario yet, but it is close enough that we have to continue to analyze it.

MR. RUMMEL: Can I ask over what period of time would they have to be heated to that temperature?

MR. HARDY: The analysis is taking it from

 

[510] 950

 

essentially lift-off or very nearly lift-off, that burning hydrogen is - the heat from the burning hydrogen is coming into that joint, to 58 seconds where we know the joint leaks. We know that without question.

There is work to be done, both in the analysis area, and we are in fact going to set up a test to pressurize a joint with O-rings and heat it from the outside and see what temperature we have to get those O-rings up to so that they would fail. So at this point in time this event is not blocked. So that scenario is still open.

DR. COVERT: When you make this experiment, obviously it is going to be on a small scale, so you are going to maintain the gap size and the compression ratio in the O-ring and those geometric factors, which means it is going to be at least big enough around so the other curvature is important, is that correct?

MR. HARDY: Yes, and we are considering putting transverse loads on it, too, the kind of loads you would have at a Max Q.

GENERAL KUTYNA: How do you simulate the air flow varying anywhere from zero to Mach 2?

MR. HARDY: Well, what we plan to do is, as best we can, is to calculate the heat rate and then we

 

951

 

 

are just going to apply that heat rate directly to the joint.

DR. COVERT: And there will be no insulation on the inside and no putty or anything like that, it would just be a clean metal gap on the inside?

MR. HARDY: Well, we will make the inside of the joint without propellant, but otherwise we will make it very similar to the flight vehicle.

MR. WAITE: Wouldn't the cooling effect of the propellant change the results?

MR. HARDY: No, I don't think so.

DR. COVERT: I would be more concerned about the chemical activity of the combustion products.

DR. WALKER: Ordinarily you bake O-rings at 250 C, so they ought to be able to take this temperature.

MR. HARDY: That is true. We estimate now that they would hold structural integrity to 600, maybe less than that.

MR. SUTTER: In a test like that you will probably run a variation of seals and variations on that to find out how much slack you've got?

MR. HARDY: Yes, we would plan to do that. We will not run a test like this, one sample test set up one way and say that's the results.

 

952

 

MR. FEYNMAN: How about if you take a clamp and you tighten it up in a glass of ice water?

(Laughter. )

DR. COVERT: The other thing, George, you might consider is seals that have been eroded.

MR. HARDY: Let me say that in these scenarios - well, let me wait until I get to that point.

DR. COVERT: I'm sorry, I didn't mean to get ahead of you.

MR. HARDY: Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-38]

[511] MR. HARDY: Now we come down to the bottom leg of this scenario, the hydrogen is still leaking from the tank, but now we are looking for cooling effect on the joint. Event A-2 says this hydrogen cools the right hand field joint. The problem we've got with that is that does not support the observations, that doesn't cause the black smoke. So the anomalous black smoke that you saw early on would have to be assigned to some other cause, but we are proceeding, recognizing the fact that the instrumentation would allow us to have a leak, and recognizing, and not be detectable, and recognizing structural integrity would allow that. We are

 

953

 

proceeding with the analysis to determine how cold we can get the joint. Preliminary analysis of that would indicate that we cannot get the joint in 58 seconds cold enough that it would seriously degrade the structural integrity of the O-rings.

So we have a temporary block on this leg of this scenario, and we haven't quit work on it, but it is not a prime candidate.

Could I have the next viewgraph?

(Viewgraph. ) [Ref. 2/13-39]

MR. HARDY: I think I have already covered this. Although we think we have blocked that leg of the scenario, we are still going to do the cooling rate analysis to see how cold it could get in 58 seconds.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-40]

MR. HARDY: Now, failing to block either one or both legs of this scenario, we come to the point that approximately at about 58 seconds there is clearly hot gas leakage around this aft field joint, and that is observed both from the film data. It is also evidenced in the tank pressurization instrumentation, and it is also evidenced by the fact that that tank is calling for more pressure to keep that pressure up. And so I think there is no disagreement on any of these scenarios that

 

954

 

we are working that eventually we get to the point where the SRM joint is leaking.

DR. WALKER: There is another sort of combined scenario in which the leak could be there before ignition and it could have cooled the O-ring and then at ignition the leak, the hydrogen leak, ignites, but now the O-ring is pretty cool, and so it may be more likely to get damaged or eroded, meaning that you have also got in addition to burning hydrogen, you have also got a weak O-ring. So you could actually combine those two scenarios in some sense.

MR. HARDY: Yes. That is one of the main reasons we haven't closed that scenario out. And you notice this scenario was built to start with the hydrogen leak at lift-off, but we need to back that up and see what happened before that.

MR. WAITE: Your hydrogen detectors don't or wouldn't be sufficient to detect this sort of a leak?

MR. HARDY: I believe Horace said the hydrogen detectors are at specific locations, disconnects in other areas where we might have some suspect for leaks, but general acreage of the tank, a survey is not covered for hydrogen leaks.

DR. WALKER: So these are near valves?

MR. HARDY: Near valves and disconnects and

 

955

 

things of that sort.

[512] Okay. I would like to go now to the next scenario which addresses the first offender being the SRM joint.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-41]

MR. HARDY: This scenario says - and I'm going to talk to each one of these in some detail, too - that I have primary O-ring blow-by. That is, I have gas past the primary O-ring. The secondary O-ring does not seal, which means now I've got gas to the outside or the secondary O-ring does seal and I have leaked past the leak check port. In either case - and I will discuss this in detail - in either case, the scenario says that the joint is either - has either leaked and stopped or it has continued to leak for this period of time from lift-off to this time here, and then we see a major hot gas leak out of that joint which goes on to the same point that the other scenario was going to take all the scenarios and with this, all the scenarios have that in it because that is well established in observation.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-42]

MR. HARDY: Now, let me say at this point, and

 

956

 

Dr. Lucas has already mentioned this, and I will elaborate on it a little bit more, but we have great difficulty analytically starting a leak or having a leak past both O-rings at or near ignition, and have that leak remain relatively well behaved, and I say that because I don't know just exactly how well behaved it stays, but to have it relatively well behaved in terms of the expansion of that leak and the leak area through that joint up to 58 seconds. But I am going to talk about that a little bit more.

But as has been mentioned here, we are looking at scenarios that - it leaks, then it seals, then it leaks again. That is not easy to come by either. This material, the O-ring material, subjected to the gas temperatures for any period of time, seconds, doesn't tolerate that very well.

DR. COVERT: You are going to talk, I assume, about combinations of these so you might have one of these that seals and then later the high load and vibration?

MR. HARDY: Yes.

DR. COVERT: Okay. Press on.

MR. HARDY: Well, let me just say now, in the scenario of the leak-seal-leak -

DR. COVERT: Let's stick with this one. I

 

957

 

didn't mean to get you off. I just wanted to know if you were going to that.

MR. HARDY: But if I don't cover that, remind me.

Looking at event B-1, which says primary O-ring blow-by, now we have that in our experience base. Our experience shows that the joint seal design can result in what we refer to as blow-by, which is during a transient build-up of pressure. While that primary O-ring is pressure actuated - could I have the next viewgraph on the right hand screen?

(Viewgraph. ) [Ref. 2/13-43]

MR. HARDY: I think you have probably seen this a few times, but the primary O-ring is located here, and the secondary O-ring is located here. The leak test port is located in such a way that we pressurize the annulus, or the volume in between here, and you have heard the description as to how that is done, I believe. It is pressurized up to 200 psi, and it is held for ten minutes, is that right - no, 15, and then that is for two reasons. One is to seat the O-rings or put the O-rings in a position where they can seal, and the other is to ensure that we don't mask a leak in the primary O-ring by the putty holding the pressure.

 

[513] 958

 

DR. COVERT: George, in Larry Mulloy's slides where that zinc chromate putty comes down and seats against the tang, his were always very carefully had a gap there, which is the real configuration.

MR. HARDY: This is not correct. That putty is terminated about halfway back up here.

DR. COVERT: Thank you.

MR. HARDY: I might say this dimension is exaggerated, too. That gap probably shows there about twice as wide as it is configured.

MR. RUMMEL: May I ask when these units are assembled, I guess they are assembled vertically and one unit goes down on top of the other and that tang goes in the clevis. Do they always go in and go home the first time, or is it necessary to pull them out or twist them or somehow displace that putty?

Do you know, in the process of assembly?

MR. HARDY: I believe that Mr. Lamberth is planning to discuss that in quite some detail, is that correct, Norm?

MR. LAMBERTH: That is correct, George. Our briefing will go into that, but to answer your question, no, we do make the measurements that ensures ourselves that we have the proper turns before we mate the joint, and we have never had to come back out unless we had a

 

959

 

leak or something like that where we had to change the O-ring.

DR. COVERT: Let me ask again, is that gap really that big between the propellant in one segment and the propellant in the next?

MR. HARDY: That is generally representative, is several inches. I can get that number.

DR. COVERT: I don't need the number. It just sort of looks like a big crack in a way.

MR. HARDY: I think you could probably put your hand in there.

MR. SUTTER: That sketch is correct in that the test port and O-rings are tied together so that you could have a combination failure of O-rings and test ports all being involved in the failure?

MR. HARDY: Yes. In fact, that is one of the scenarios I will talk about. But what I wanted to make here, talking about the incident of the blow-by, I guess what I'm trying to say is that we have experience, event No. 1, we have experienced it several times. So I don't have to prove that can happen because in fact it has happened. I was just explaining the primary reason for it to happen is when we do pressure check here, this graph doesn't show it too well, and I've got one later that shows it a lot better, but this O-ring, the primary

 

960

 

O-ring can move back and does move back against this edge of the groove, and the gap between the other side of the O-ring and this other side of the groove, of course, depends upon several things, not the least of which is the diameter of the O-ring. But it also can be because of the allowable dimension on this groove here, it can be anywhere from 15 to 30 mills.

So when the motor is pressurized and the pressure first hits this O-ring, this is what we refer to as pressure actuating. It has to move back to the side.

Now, I am going to go into more detail about that with some better diagrams in just a few minutes, but I only wanted to point out that we believe that that is where we occasion what we call blow-by. But we do know from experience that you can establish for a transient period of time some blow-by of the primary O-ring. In every case it has been limited. It has been limited [514] by the sealing, first of all, by the fact that the secondary O-ring is sealed, the leak port has sealed, so there has been no way for the gas to continue flowing.

Could I have the next viewgraph, please?

DR. WALKER: Before you do, I just want to ask a couple of questions on that.

How many threads are engaged in that plug, in the leak check port?

MR. HARDY: I will have to get the answer to that.

DR. WALKER: I don't see the steel band. It is not shown.

MR. HARDY: The steel band is right here underneath the cork. What is represented here is a shim, and I will talk about that a little bit later.

DR. COVERT: George, Larry Mulloy again said there were two O-rings on that leak check port, and your diagram only shows one.

MR. HARDY: There are two O-rings on that, and I will get this diagram corrected before I show it again.

DR. COVERT: I don't mean to be a nitpicker but as you know, I get confused easily.

MR. HARDY: I think that is a good point. We should represent truly what it looks like.

Could I go to the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-44]

VICE CHAIRMAN ARMSTRONG: That is threaded, too, isn't it?

MR. HARDY: Yes, it is.

Now, this is the incident of blow-by that we

 

962

 

have seen on the primary O-ring, and I think most of you heard a good bit about this in Washington. But I just wanted to show that we have had four instances of blow-by, and I distinguish blow-by from O-ring erosion because those can occur together, they don't have to occur together, and in fact, there is a slightly different mechanism that causes each one of them to happen.

There does, for just a matter of interest, seem to be focused around this leak check port area here. Now, we have at this point in time assigned - haven't assigned any great significance to that. It may well have to do that this is where the gas enters to do the leak check, and there may be some more disturbance of that primary O-ring pushing it back in that area versus in the other area.

GENERAL KUTYNA: That's a contradiction of what we heard in Washington because we asked Mr. Mulloy at least twice, was there any area in which this was localized, and he said no, it was pretty well distributed, and you are now saying that it is at that bottom of the Z axis.

MR. HARDY: Well, Larry may have been referring to the fact that it is not total. We do have one over here, but I will check my facts on this, but

 

963

 

I'm pretty sure I'm correct.

DR. WALKER: Maybe he was talking about the erosion rather than the blow-by.

MR. HARDY: Now, that is true on the erosion. In fact, the open circles is where we've had erosion, and the half-opened, half-closed is erosion and blow-by. So on erosion you can see that there doesn't seem to be any pattern where you've got erosion on the O-rings.

GENERAL KUTYNA: And yet he did say that given the choice between the two, the blowby was the more serious.

MR. HARDY: Yes, and I agree with that because the blow-by can in fact get us through the first event in this failure scenario.

[515] Could I go to the next viewgraph, please?

MR. FEYNMAN: I hope it's not improper to bring up something slightly different. The question is whether there is a correlation between the blow-by and the accuracy with which the gaps and so forth were fitting, the mechanical fit of the particular joints when they were put together. There must be, of course, all kinds of records, and you must have heard that a million times, does it turn out the blow-by occurred when the gaps - -

 

964

 

MR. HARDY: There's a number of things that we are attempting to correlate blow-by with, environmental conditions, specific configuration of that joint, material vendors, whether there were more than one material vendor, was there one material that performed a little bit better than the other, and as you correctly state, the dimensions, specific dimension of each joint, and we are correlating all of that, and we see some correlation in certain areas.

I am really not prepared to talk about it right now because I can't remember all of the details.

(Viewgraph. ) [Ref. 2/13-45]

MR. HARDY: The second event I would like to go to first is to take this trail down here and look at event B-2. This says if I get blow-by of the primary O-ring and this leak check port is leaking, the first question we ask ourselves, could this anomalous smoke starting at or near liftoff, could that be from the leak check port, and I guess there is some difference of opinion among the film analysts at this time, and I am not going to try to pick sides, but I am going to work to find out which one is right, that there is film that says that we can see the leak check port, you heard that discussion earlier, whether we really know whether we are looking at the right place, that say you can see the

 

965

 

leak check port, and the leak check port is not leaking. At this point in time we have not put a block on that. It may get blocked if in fact we can verify from observed data that that port is not leaking.

DR. COVERT: George, what is the diameter of that leak check port?

MR. HARDY: Three-eighths is the number I remember.

DR. LUCAS: But it's a one-eighth inch hole.

MR. HARDY: Yes. You saw from the drawing that the hole that went directly into the cavity is one-eighth inch. But as long as we can block this - as long as we can't block this, then we look at the analysis to see what are the thermal flow characteristics of this leak check port. If the leak check port is leaking, it could be several things, theoretically, that could cause it. One would be missing O-rings. The other would be not missing O-rings but damaged O-rings. The other potential could be lack of proper torque.

Now we set up a series of tests. That is shown right here.

DR. WALKER: Do you know that the plug was there?

DR. COVERT: I think if the plug wasn't there,

 

966

 

when we looked at that white paint, although three-eights is pretty small compared to that - -

DR. WALKER: Do you have some photographic evidence?

DR. COVERT: We looked at it. Didn't we look at the closeout pictures of the ring?

MR. HARDY: I don't know if we have close-out pictures on the photos or not.

[516] MR. LAMBERTH: Yes, George, there are - a close-out photo is not required, but in the area you can see the hole there, and you can argue about the plug being there or not. It looks like it is there, and all of our paper and everything shows normal, buy-off and everything normal.

DR. COVERT: On that Eastern airliner that lost those O-rings in the oil, they had all the right paperwork, too.

MR. LAMBERTH: George, just to kind of correct the record, the drawings and everything, in our architecture there is one O-ring on the leak check plug.

MR. ACHESON: In real life there is one?

MR. LAMBERTH: Yes, and this is a plug and an O-ring.

MR. HARDY: So this chart is correct. I had

 

967

 

heard that two different ways.

But in any case, what we want to do is characterize the leak. What would be the leak rate for various conditions of anomalies of that plug? And that is important in order to determine - to do the flow analysis and the thermal analysis. And we have done the thermal analysis and determined that for any leak rate we just about we want to pick out of that plug, whether we want to consider the plug is gone, the O-ring is gone, or neither are gone, but there is a very low leak rate out of that plug, we have determined that the secondary O-ring will degrade and erode to the point of failure before the threads are heated to lose structural integrity and blow the plug out.

So as I said, very key in this scenario is coming to some grips with whether or not that might be the source of the black smoke because this scenario would fit the incident of a small leak early on, and then the joint failing at 58 seconds.

MR. FEYNMAN: This way the idea is that it starts to leak through the leak check port, through the primary, and that perpetual gas going through there ultimately destroys the secondary O-ring?

MR. HARDY: That is correct. The thermal damage and strength loss in the threads would not be

 

968

 

sufficient for it to go 58 seconds, but the secondary O-ring erosion would.

Now, in characterizing this leak, we are going to do cold flow and hot flow tests because I believe, as Dr. Lucas also mentioned, we believe that it would be possible to get let me say, a relatively high leak rate out initially, but as the aluminum oxide and other products of combustion flow through those threads, it would tend to slow that leak rate down.

So we are using a variable leak rate in these analyses. But in every case we see a secondary O-ring failure before we see the leak check port.

GENERAL KUTYNA: Why is that secondary O-ring eroding? There is no flow; there is stagnation at that point.

MR. HARDY: Well, if I am flowing through here and I am flowing out here, I am pumping heat into this gap.

MR. FEYNMAN: It is circumferential.

MR. SUTTER: The first ring is getting cooked fast, but the second one could last a lot longer because there isn't flow by it.

MR. HARDY: Well, there is flow into this cavity.

MR. SUTTER: But if it is sealed, it isn't

 

[517] 969

 

flowing- -

MR. HARDY: But if I am pumping 5,000 degree gas in here, in order to get out right here, I am severely degrading that O-ring.

MR. SUTTER: But I am just curious, is that plug, what I see here is just a plug screwed in and some guy torques it, and there's no locking device on it?

MR. HARDY: You are correct, to my knowledge, that is correct.

MR. SUTTER: Are there other nuts and bolts like that, too? It doesn't seem like a standard design practice. I am just curious.

MR. HARDY: Well, it is a standard design process for a lot of electrical connectors and many of the structural fasteners.

DR. WALKER: Did you say it is locked tight?

MR. HARDY: It is standard practice to lock wire or lock tight electrical connectors.

DR. COVERT: This is aluminum tightened into a steel. Is there some sort of a frictional seizing, like if you put brass into steel and tighten it down, why, then there would be a sticking there.

MR. HARDY: This plug is steel.

DR. COVERT: Where did I get the idea it was aluminum?

 

970

 

MR. HARDY: I'm not sure.

(Laughter.)

MR. SUTTER: The only safety of that system, then, is quality control?

MR. HARDY: That is correct.

MR. SUTTER: And it is a single item.

MR. FEYNMAN: Well, it is supposed by itself not to be a problem because the primary ring is supposed to hold. That is why it isn't at the same level as we are now thinking about it, and we now are thinking about primary rings failing, and that hasn't been communicated that the check valve therefore becomes a critical item.

MR. WAITE: Would you say if the plug were left out that you would have O-ring failure? MR. HARDY: No, I would not say that. I would not like to have the plug left out because, as I experienced for occasions of blow-by, if it was in one of these cases, then I think I would be in for trouble.

MR. WAITE: Then you would have flow that would cause the secondary seal to degrade? MR. HARDY: That's right.

MR. ACHESON: In cases of blow-by past the primary ring, what is your experience on the condition of the plug and the check port?

MR. HARDY: In every case that we have seen

 

971

 

blow-by, we have post-recovery, in examination of the article, has shown that that blow-by is limited to soot deposit back here, and on no occasion have we seen any violation of the secondary O-ring or any violation of the leak check port here.

MR. ACHESON: I see.

MR. HARDY: If I might go on to the next one and mention that this track stays open for the time being, and now I would like to look at the B-1 event.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-46]

MR. HARDY: Now, the B-1 event follows the blow-by on the primary O-ring, and it says that - and these are for the secondary O-ring seals, and therefore I establish flow past both O-rings, the anomalous smoke starting at or near lift-off could be from that field joint, and it could be from gas passing through both O-rings. And I think it has already been mentioned the grease in this joint. From that grease we would see black smoke. We have identified in the investigation a suspect secondary O-ring which is indicated in the close-out photos, and let me hasten to mention before we show you this that we are still collectively trying to interpret these photos. It is not immediately obvious what we are

 

972

 

[518] seeing, and that is the reason I classified it as a suspect close-out photo. I have some viewgraphs, and Bob looks like he has got a big blow-up, and so let's put the viewgraphs on, please.

The next viewgraph.

(Viewgraph. ) [Ref. 2/13-48]

MR. HARDY: No, I'm sorry. They are out of order.

Do you have the picture viewgraphs?

Take down the viewgraph on the right hand screen.

Jack, could you help me back there get the picture up?

(Viewgraph. ) [Ref. 2/13-47]

MR. HARDY: You can probably see better on what you have there, but what you are looking at, maybe I can locate you the features and then you can look at the blow-by that you have.

What you are looking at is a clevis. This clevis has been prepared, this is the upper side of it, and this is the inner leg that you are looking at. The primary O-ring is here. This is a land in between the primary and secondary. This is metal, and this is the secondary O-ring right here. And these are close-out photos that are taken as a part of the process.

 

973

 

I might mention to you this joint. The metal, before the O-rings are put on, the metal is greased. We put a heavy coating of Conoco grease, which is a stiff grease that is put on this joint, and it is put on there for two reasons. One is, the primary reason is to provide corrosion protection for that joint, and the other is to provide ease in assembly of the installation of the O-rings. The O-rings are delivered prelubricated from Thiokol to Kennedy, certified ready to install, and the secondary O-ring is put on, and I am not going to go into great detail about this because you are going to hear a lot about it and maybe even see it tomorrow, but the secondary O-ring is put on around the vehicle, over this joint, and then the primary O-ring is put on.

And what we view, the area right here in the secondary O-ring, that gives some appearance of depression and raised area, and it also gives some appearance, and you can probably see it a lot better in what you've got, of the reduction in cross-sectional area of the O-ring.

Now, if I could have the next viewgraph.

(Viewgraph. ) [Ref. 2/13-48]

MR. HARDY: We have a picture of one here that has been somewhat enhanced, and again, not too clear up here is the primary O-ring, and this is the land between

 

974

 

the two grooves, and this is the secondary O-ring, and this is the area of interest, and here is the area which concerns me, indicating some reduction in cross-sectional area.

DR. WALKER: It looks like a gouge almost.

MR. HARDY: Possibly.

[519] MR. FEYNMAN: What is that slightly white area? Do you mean that slightly white or black area in there?

MR. HARDY: In here.

Let me explain what we do know. What we do know is that there is, as I mentioned, this joint is greased rather heavily, and we are quite confident that this is grease that is smeared across here either at the time of application or installation of the O-ring. Again, without getting into too much of what you are going to hear tomorrow, after the O-ring is put in place, the operators with surgical gloves, with greased fingertips, do by procedure go around and push this O-ring into the groove, make sure it is fitting in the groove before they mate the joint.

So there is a question as to whether this represents grease smears also or whether it is some form of a distressed O-ring, and I use that term because I would not describe it as a twist; I would not describe

 

975

 

it as, at this point in time, as a deformation. I will only say that without being able to totally interpret it at this time, it is a piece of data we are working with. We have some photo enhancement activities going on with expertise that we believe can give us more insight into whether or not that is grease smeared across the O-ring or whether that is in fact some form of defect in the O-ring.

GENERAL KUTYNA: Is this the flight motor or is this just a sample?

MR. HARDY: This is the flight motor.

GENERAL KUTYNA: Is this the flight joint?

MR. HARDY: This is the flight joint.

DR. WALKER: That particular one down there?

MR. HARDY: It is in the correct hemisphere. It is on the inside, and it is not in the same quadrant as the point where we see the blowing leak. All I can say at this time, it is in the right half of the motor. It is in the half of the motor adjacent to the external tank.

CHAIRMAN ROGERS: Can you tell us how this picture was taken? I assume - when? When was it taken?

MR. HARDY: It was taken as a matter of procedure when this joint was being made.

 

976

 

CHAIRMAN ROGERS: What is the purpose of the picture?

MR. HARDY: It is what we refer to as closeout photos, and there are a number of operations here at Kennedy that require that closeout photographs be made. These closeout photographs can be used for many purposes. In some cases they can be used as a quality assurance validation, and in some cases they can be used in anomaly investigations.

CHAIRMAN ROGERS: What about this case?

MR. HARDY: In this particular case, Horace, I will let you explain it.

MR. LAMBERTH: These were closeout photos sir. We had photos that covered the entire 360 degrees of the putty lay-up and so on.

CHAIRMAN ROGERS: Somebody looked at this ahead of time but didn't notice it?

MR. LAMBERTH: That's right.

DR. COVERT: The inspector did not call attention to this change in the gap?

MR. LAMBERTH: No, Sir.

DR. COVERT: Well, how much could you see on that without having to call it? What is the spec on that?

MR. LAMBERTH: We did not have a spec.

 

[520] 977

 

MR. RUMMEL: There appears to my eyes to be a ridge, a small ridge around the secondary O-ring. Is that - -

MR. HARDY: We believe that is the grease that it picked up when it was rolled over the edge of the groove. That is our best guess.

MR. LAMBERTH: George, all of the engineers and all of the techs and the QC and advisors looked at this photo still feel that this is a result of the grease streaks and shadows, but nothing was written on any notes or anything when we actually made the close-out photos and made the joint.

CHAIRMAN ROGERS: Do we know who it was that signed off on this?

MR. LAMBERTH: Yes, sir.

CHAIRMAN ROGERS: Is that person - does he say he didn't notice this?

MR. LAMBERTH: We haven't interviewed that particular person formally yet. On all of the notes, they make notes of anything that they notice or anything, and none of the notes - all of the notes have been reviewed, and no notes specify anything.

CHAIRMAN ROGERS: Is there more than one person who does this?

MR. LAMBERTH: Yes, sir.

CHAIRMAN ROGERS: In other words, is there

 

978

 

somebody who looks at this and signs off on this, and then somebody checks him?

MR. LAMBERTH: It is about four or five techs that put the O-ring in, and then they go around with gloves like George said, and QC goes around and makes a circle and looks.

CHAIRMAN ROGERS: But I am talking about the picture afterwards. You take the picture, and the picture is taken in order to see if - -

MR. LAMBERTH: The picture is not part of the logoff records. Sometimes the picture does not get looked at.

CHAIRMAN ROGERS: Why is that?

MR. LAMBERTH: Well, there is a requirement to make these photos and document that they have been made and log them. The buy-off is the actual visual inspection at real time. The photos are for records.

MR. FEYNMAN: You talk about the streaks on the metal. For the moment I am not concerned with that on the O-ring, but the streaks like that - are streaks like that on the metal very common?

MR. LAMBERTH: Yes, sir.

MR. HARDY: The grease streaks would be, yes, sir.

MR. FEYNMAN: They look more or less like

 

979

 

that.

MR. HARDY: Yes, I believe that is the case.

MR. FEYNMAN: Thank you.

DR. WALKER: Could I raise a question?

Shouldn't you expand your scenario backward, because suppose there's a low point in the putty and the putty doesn't seal properly? That could be a problem as well.

MR. HARDY: We do have the putty in the failure scenario. One particular aspect is the putty is cold, and how does cold putty affect the performance of the seal?

[521] DR. WALKER: But suppose there is a low point in the putty here which leaves a gap? Is there some inspection of the putty? Does somebody measure the uniformity of the putty?

MR. HARDY: Yes, it is, and I need to point out to you, I don't know the exact dimensions, but as you see that putty there, it is up I'm going to say three-fourths of an inch or so, or in the neighborhood of three-fourths of an inch, and that is compressed into I would say a third or less of that dimension.

DR. WALKER: But there could be a gap in there.

MR. HARDY: We do believe, however, that the primary O-ring erosion occurs when we have what we refer to as a blow hole through the putty. So we can concentrate hot gas on the primary O-ring. So weak places in the putty, weak relative to other places in the putty where the gas would go through first could be a contributor to primary O-ring erosion, the primary O-ring erosion that you heard about yesterday or the day before, I have forgotten which now, in Washington, which we believe is a limiting failure mode.

CHAIRMAN ROGERS: I would like to go ahead with this.

When was the picture taken prior to launch?

MR. LAMBERTH: We stacked in December the 7th, so it was right about that timeframe.

GENERAL KUTYNA: On the back of the picture it says 12/7/85.

CHAIRMAN ROGERS: Now, you said sometimes these were looked at for safety purposes and sometimes they weren't.

How do you make that decision?

MR. LAMBERTH: Well, usually these are placed on record, and many times they are looked at by a group of people just looking at closeout photos, and review might occur a week or several week afterwards. The procedure does not require a review and a verification

 

981

 

of the closeout photos. It requires a verification from the staff that the closeout photos are taken.

CHAIRMAN ROGERS: Was that practice changed? Did you used to do that? In other words, did you use to take the picture and then look at it before you signed off?

MR. LAMBERTH: No, sir.

CHAIRMAN ROGERS: It has always been that way?

MR. LAMBERTH: Yes, sir.

MR. HARRINGTON: The corresponding requirement for this is for postflight analysis of an anomaly.

MR. LAMBERTH: This is for questions that might come up later in the paper or anomalies.

MR. RUMMEL: A picture is taken at the time of the visual inspection, prior to the accident

MR. LAMBERTH: Yes, sir. We have a requirement that after we put the joint in the configuration that you see it here, from the time we start this joint to the time we mate is 24 hours, so the picture and the work all gets done within that period of time. We actually did this one in about ten hours.

CHAIRMAN ROGERS: Just because you are going to be asked eventually a lot of questions about it, what is the purpose of keeping the picture if you are not

 

982

 

going to look at it before launch?

MR. LAMBERTH: Just like we are doing here now, sir, so that if some question comes up on the paper later that some anomaly or some question - -

[522] MR. HARRINGTON: A record of the condition that gets closed up by the flight configuration that you can look at later to examine it in the case of an anomaly, which we are doing.

CHAIRMAN ROGERS: But it seems illogical if you are going to save it for a record to show the failure.

MR. HARRINGTON: Well, you see, if we didn't know today there were two O-rings in there, and we didn't have a picture, we would have a difficult time ascertaining that somebody did put two in. We would have to take the word of the paperwork trail and the inspector. In this case we have a picture that says they definitely were there.

CHAIRMAN ROGERS: I just don't follow that. Why is it better after the fact to look at it than before the fact?

MR. LAMBERTH: Well, let me clarify that. Real time we have a buyoff by the technician that does the work, by a contractor inspector and a NASA inspector that this job was done properly and all the inspections

 

983

 

were made, that is, by visual and buyoff procedure.

CHAIRMAN ROGERS: Let me press that point just for a moment.

So you have two humans or three humans that look at it.

MR. LAMBERTH: Yes, sir.

CHAIRMAN ROGERS: And then you have a record, which is even better, because it shows it.

Now, if you don't compare the record ahead of time with what the humans have done, and now you have a record that the humans failed because they didn't see this, and assume that's a fact, now, what is the point of having the picture?

I mean, it would seem to me that this may explain the failure after the catastrophe?

MR. FEYNMAN: Might I make a suggestion? Just as a suggestion as to what, it might be a very logical reason for doing this, whatever procedure you use, no matter how many inspections you use with people and whatever, then you have to decide sometime to close it up. It would be very handy to have a record to look at later in case there is some kind of a thing that you didn't know was important because you find some kind of a flaw, let's say blow-by. Later on you want to discover what did you do. You discover that every time

 

984

 

there is a blow-by, there is a little extra grease mark that you hadn't realized was of any importance, and therefore the record would be very useful when looking at the thing later to discover whether something that you are not considering as important, which you are allowing to pass. That is, let us suppose that the usual rule is that when an ordinary human being looks at this picture he doesn't think there's anything wrong with it, which as a matter of fact, I do think there is nothing wrong with it. So it would pass everything, but the real thing is you would like to get a record of what it looks like so that in case later on you discover there is some other condition that too much of this grease or something like that, or a special color grease that you never knew or that you changed or something like that becomes of importance, but you hadn't realized that when you were putting it together.

And I see therefore some logical reason to have such records.

MR. CRIPPEN: Mr. Chairman, I guess that is our standard practice for keeping records, not for inspection, and in fact, I would submit that probably somebody - if somebody had inspected this picture while it was being put together, at a later point, and we had not had a problem, that it would have probably gone

 

[523] 985

 

through and been looked at because it is still not obvious to even all of the experts looking at it today that that is really a problem area. It is just something that we - since we know we had a problem in this area, that looks a little bit different and people are out exploring.

DR. COVERT: In fact, Mr. Chairman, the fact that there is no specification calling for more than a minimum acceptable gap or a maximum acceptable gap suggests what Mr. Crippen is saying is so. If there is no spec to measure it against - -

CHAIRMAN ROGERS: Well. I guess I understand. I am not convinced. I think it is going to be difficult to explain if you have - maybe the answer is that you didn't think you could find anything by looking at your pictures, maybe that is a better answer.

MR. RUMMEL: I think there might be some validity to that because the human eye looking at that object in three dimensions I think usually is far more accurate of the perspective.

CHAIRMAN ROGERS: That is a better answer to me. It seems to me the human inspection is better than a visual inspection, a photographic inspection, but I'm not sure people are going to be convinced by that.

VICE CHAIRMAN ARMSTRONG: May I ask, the

 

986

 

yellow, is that the putty or is that the insulation, the yellow material?

than photographs because

MR. LAMBERTH: That is the putty.

CHAIRMAN ROGERS: In this case, do we know who the ones were who looked at it visually and signed off on it?

MR. LAMBERTH: Yes, sir.

CHAIRMAN ROGERS: How many were involved?

MR. LAMBERTH: It is four people who usually handle the O-rings, and then we have a NASA QC and a contractor QC, and the technicians.

DR. COVERT: Could I ask a different question that has to be asked at this point, not directly relevant. In this organization, does QC report directly to the Director independent of the manager?

MR. LAMBERTH: Yes, that is correct.

MR. SMITH: Let me clarify the point. There is a quality organization within the Shuttle Directorate, the Shuttle Operations, under Bob Sieck, that does report to him. I have a center quality organization that is a procedures and holding function. That does not do the detailed inspections. The detailed government inspectors in this case do report to Mr. Sieck.

DR. COVERT: Is there the possibility - and I only raise this as a devil's advocate viewpoint, but is

 

987

 

there a possibility that there may be a mild conflict of interest here because the guy on the one hand who is responsible for quality control and safety of the Space Transportation System reports to you, and you are also the man who is responsible for maintaining schedule and all of these sorts of things? And I don't mean to imply you are putting any pressure on your safety people or anything like that.

DR. SIECK: Well, that is a tough one to answer.

DR. COVERT: I did not mean to say when did you stop beating your wife?

MR. SMITH: Gene, I have gone through that process several times since I have been here. I have asked that question, I have talked with people. I have in my own mind been absolutely [524] convinced that we do not have a conflict of interest, primarily because the first charge is a safe launch and not schedule. And I know at least 300 times I went through and made sure to my personal satisfaction that that was not a conflict because I recognized the apparent conflict.

DR. COVERT: You understand - -

MR SMITH: Absolutely, I understand the question.

DR. COVERT: Thank you, Mr. Chairman, for that.

CHAIRMAN ROGERS: Going back to the picture for a moment, do you have pictures of, a lot of previous pictures of the O-rings from previous launches?

MR. LAMBERTH: Yes, sir.

CHAIRMAN ROGERS: And do you now, looking back at it, find other suspected areas?

MR. LAMBERTH: I am not prepared to answer that, sir. I don't know how many we have looked at. I am not aware of that. I need to check how many we have gone back and looked at.

CHAIRMAN ROGERS: How did you find this one?

MR. LAMBERTH: This was the inspection. We formed a special team to go back and rereview all of the procedures involved in this specific launch and review the closeout photos and all documentation, and it was reviewing these closeout photos where we picked up this.

CHAIRMAN ROGERS: But that was just 51-L that you reviewed?

MR. LAMBERTH: Yes, sir.

CHAIRMAN ROGERS: Thank you.

GENERAL KUTYNA: The team that stacked - this was a restack of this particular segment, is that correct? Didn't you stack it once and take it down and restack it?

MR. HARDY: No. I think that was incorrect

 

989

 

information. There was another segment that was initially designated to be stacked here, and there was a redesignation of segments.

MR. LAMBERTH: George, we are going to cover that in our briefing, and we will go through that specifically, but the answer is no, sir.

MR. HARDY: Let me just say this about the picture. I cannot interpret the picture. I do want you to know, however, that we have engaged and are in the process of engaging what we believe to be the best photographic enhancement and photographic interpretation assistance that is available, and that should be going on, if not in fact today, within the next day or two.

CHAIRMAN ROGERS: Could I just make this one comment?

I appreciate, as Chairman of the Commission, that you showed us this photograph and enhanced it and made it available to us. I mean, it is the kind of cooperation that I think is very important, and you are to be commended for it.

MR. HARDY: Let me just mention one other thing that we are also going to do in the task of trying to interpret this picture is that we have set up on the full scale segment to try to simulate as nearly as possible what we see here, and prepare the joint, put

 

990

 

the secondary O-ring on, the primary O-ring, and we will do at least three things that we can think of and anything else that we can think of around that O-ring, that we will twist it, we will smear grease on it, trying to match that pattern of grease as nearly as we can. We will indent it, deform it. We will do the things that we think might simulate that.

[525] Then we plan to take photographs as best we can matching the camera angles, the lighting conditions, the distances and so forth, to see if we can make any reference photographs which would lend any support to interpreting what we see there.

DR. COVERT: George, just one other thing, and I hate to always go back to what Larry Mulloy said, but he led me to believe on Tuesday that in fact people did measure the diameter of the O-ring at the time that the O-ring was taken from its envelope, that there was essentially a receiving inspection procedure?

MR. HARDY: I am sure Larry knows.

DR. WALKER: That was only every two feet.

DR. COVERT: But if there was a ding in it - -

MR. HARDY: I know Larry knows how this is done, and maybe we have a miscommunication here, but the O-ring is measured at Thiokol. It is lubricated at Thiokol. It is placed in a sealed bag, and it is

 

991

 

delivered here certified flightworthy, and the inspection here is to ensure that the bag has not been opened, to make sure there has been no tampering with it.

But there is no requirement on KSC to verify the O-ring diameter. In fact, with the grease on it, it would be difficult for them to do.

DR. WALKER: So Thiokol measures the O-rings.

MR. HARDY: Yes.

DR. RIDE: Has that always been the case, that KSC hasn't verified the diameter?

MR. HARDY: It has not always been the case that KSC received it unlubricated, and I don't know whether you verified diameter or not, Horace.

MR. LAMBERTH: There was a time that we did do inspection of the O-ring, and I am going from recollection. I think part of the diameter checks, the interval was part of that.

DR. RIDE: When you used to do that, did you always find that they were within spec as measured by Thiokol?

MR. LAMBERTH: I asked for that record, Sally, and I know we had some questions about the O-rings, and there had been some that were, say, not usable, but I'm not for sure what was the reason. But what George says,

 

992

 

today, we receive them in the bag, we inspect the bag, the bag is intact and sealed, and unless we see something very obvious when we take the O-ring out of the second bag, it is a plastic bag inside of a paper bag, and unless we see something obvious, we just install the O-ring.

MR. MOORE: Our task force is going back to ask for those records Sally.

CHAIRMAN ROGERS: Assuming this is some kind of an anomaly and not just a distortion of grease on the photograph, that there is some kind of a defect here, is it possible that the defect would be on the part of the manufacturer or the contractor, or would it be always in connection with the installation?

MR. HARDY: I think it could be either one.

DR. LUCAS: The same contractor does both.

MR. RUMMEL: Could it have occurred during the shipment or storage, where the O-ring is wound up and compressed? That sort of thing.

MR. HARDY: I think that is possible.

MR. RUMMEL: I think it would be normally expected if, in fact, that is the way it is stored.

CHAIRMAN ROGERS: Thiokol is responsible for that, too?

MR. HARDY: Yes, sir.

[526] MR. SUTTER: Is there a lot of equipment that

 

993

 

is inspected by whoever makes it, and then it is just put on the vehicle without a receiving inspection here?

MR. HARDY: I'm not aware of a lot of that equipment, but I could defer to Mr. Lamberth at KSC.

MR. LAMBERTH: I think the answer is no, there is not as lot. I think the purpose - it is my understanding when this decision was made, it was a time consideration, that the process we go through in putting up the putty and everything, you know, you do have a requirement to try to lay the putty up and put the O-rings in and make the joint in 24 hours, and I think that the time to try to inspect the O-ring to that depth and lubricate it and everything was why the decision was made to go ahead and lube it and ship it in that way.

MR. SUTTER: It seems to me the guy who is lubricating the O-rings shouldn't be fooling around with the joint.

Was this considered to be a noncritical item, or it just seems to be a false economy.

MR. HARDY: It has always been a critical item, and one of the reasons, too, was to have it lubricated at Thiokol, the manufacturer, the motor manufacturer's plant, was because the lubrication of the O-ring is a critical operation.

MR. SUTTER: Doesn't Thiokol join this thing?

 

994

 

MR. HARDY: Yes, sir, the same contractor.

DR. WALKER: I thought Parker manufactured this.

MR. HARDY: The rubber is from DuPont or 3M. It is molded by Parker-Hannafin, and then it is joined together and made O-rings out of it by a company called Hydropack, which delivers it to Thiokol.

Just one other thing that did have to do with the decision to have it packaged at Thiokol was that there was some experience - and Horace, you may remember this - that this O-ring is a very large O-ring with a large diameter, and there was experience here at Kennedy of getting it contaminated when putting grease on it, getting contamination on the grease. This was having to be done in the Vertical Assembly Building where it was not contamination controlled, and so it was judged that it could be processed at Thiokol, we could ensure that we got the right grease on it, and we could deliver it without any contamination in that grease.

DR. COVERT: Is it inspected by a NASA inspector at Thiokol prior to bagging and shipment?

MR. HARDY: Yes, sir. There are mandatory inspection points requiring government inspector buyoff.

Now, if I can leave the O-ring, that suspect

 

995

 

O-ring for a moment, the other observation that is of great interest to us regarding the part of the scenario that says the secondary O-ring leaked is the launch environment and the temperatures.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-49]

MR. HARDY: This shows the temperatures at the various nodes indicated here around the SRB, the right hand SRB, and this goes back roughly 70 hours, I believe it is, from the time to [527] launch, and the arrow here is at or very near the time of the launch, and this shows what the temperatures did through the night and where we were at the time of the launch.

MR. FEYNMAN: Is this calculated because there is a delay in cooling the steel? Otherwise you would have no way of predicting where it was going to be - the delay of the arrow is the inertia, the thermal inertia of the steel?

MR. HARDY: The model is just set up to run it for this period of time, and we just picked the actual launch time up here, but you can see, I believe, that the coldest temperature was in this area here. At the time of launch it was around 25 degrees. The other side of the booster was at near 47 degrees.

DR. COVERT: Does the sun shine on that side?

 

996

 

MR. HARDY: I believe this side here is exposed to the sun, right in this area.

GENERAL KUTYNA: And where do we postulate the leak?

MR. HARDY: In this area here, this general area, well, first of all, somewhere on this side of the booster, and the very evident leak at the point in time, about the 58 seconds, is in this general area here.

Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-50]

MR. HARDY: The question was asked this morning about the gradient in the propellant. This is 51-L's curves. This shows the propellant next to the case, the insulation, and then the outer propellant, the outermost propellant and the inner propellant, and I believe that is about 19 degrees.

Of course, the mean bulk, which is the average temperature you see here, and you can tell that over the temperature excursions of this type, the temperature changes practically not at all.

The next viewgraph will show you that.

DR. COVERT: Could I have a copy of that, George?

MR. HARDY: Sure.

The next viewgraph, please.

 

997

 

(Viewgraph. ) [Ref. 2/13-51]

MR. HARDY: Just for information, I have shown on a previous flight, this was flight 51-C, the outer propellant temperature and inner propellant temperature on that particular flight was about the same, about 18, 19 degrees difference. The mean bulk temperature on this flight was a little bit lower than on the previous flight, a little bit lower on 51-L.

Could I have the next viewgraph, please?

DR. COVERT: What caused that cycling of the temperature?

MR. HARDY: It is the hourly cycling of the ambient temperature.

DR. COVERT: The time scale I didn't read carefully.

MR. HARDY: If these viewgraphs are not in your handout, I will make them available.

GENERAL KUTYNA: They are not.

MR. HARDY: Then I will make those available.

(Viewgraph. ) [Ref. 2/13-52]

MR. HARDY: In summary, from what you have seen off of the curves, just putting it on a table here with the model, using the coldest ambient temperature and the relative humidity, the wind direction you can see there, and the cold sky for radiation, this is the

 

[528] 998

 

cold case, the nominal case using the more nominal sky temperature for radiation, the aft segment in the coldest case. We predict the case temperatures at launch would be around 25 degrees at one location, and around the other side, about 47 degrees.

A more nominal prediction you see wouldn't be a vast change in that. There wouldn't be a vast change in that, and for the forward joint, the forward segments, the joint temperature on the right hand booster would be about the same.

Now, we are going to talk about these temperatures. I just wanted to show you that the forward segment on that side and the aft segment temperatures were essentially the same.

Could I have the next viewgraph, please?

MR. ACHESON: And we can assume the O-ring temperatures would have been the temperatures corresponding with those numbers?

MR. HARDY: Yes, very, very close.

MR. FEYNMAN: What did you mean by forward?

MR. HARDY: The forward field joint, these are these two joints here, and these aft field joints on the right hand booster at approximately the same clock orientation, or about the same place.

(Viewgraph. ) [Ref. 2/13-53]

 

999

 

MR. HARDY: Now, this is a busy chart, and I have it in your handout, and there was some interest expressed in this, I believe, on what are the dimensions of the joint, and I will not try to go through all of these, but I will point out some of the more significant ones having to do with the establishment of squeeze on the O-ring.

This is - well, first of all, this is a sealing surface on the tang, and this is the orient locations, and this is a picture that shows this just a little bit bigger, these radial dimensions on this sealing surface, and this interclevis leg sealing surface, dimension C and dimension D on 51-L were as shown here, 144.574 inches, and 144.566 inches.

DR. COVERT: That is an average of a bunch of readings around the ring?

MR. HARDY: Yes. This is done on the lathe.

VICE CHAIRMAN ARMSTRONG: Is this at a specific temperature?

MR. HARDY: At ambient. This is done at the case manufacturer, which is Rohr, Incorporated, in San Diego, and it is done on the lathe, and it is done, Neil, at just an ambient temperature.

DR. WALKER: It is not done after they are flown and recovered?

 

1000

 

MR. HARDY: No, it is not.

DR. COVERT: So this is as delivered to Thiokol for loading?

MR. HARDY: That's correct, the first time. Yes, specifically dimensions C and D.

Now, I am going to talk about some other dimensions that are made after every use, but this is the dimensions, the regular dimension on these sealing surfaces, and that is done the first time on a lathe at delivery, and in fact, that could only be done on a lathe. These steel, relatively thin-walled steel cases with the large diameters they have, there is no way you could actually make those - you could make some pie tape checks on it, but it is just not round. It never sits round, perfectly round. There are, however, requirements on the contractor Thiokol that if they have any occasion to repair any of the sealing surfaces - and there are repair procedures - that in the event there is any salt water effect - and I mentioned where you have the grease on it to [529] prevent any corrosion - but if there is any pitting corrosion, there are specifications that allow repair to remove that pitting corrosion. There are specifications, and I don't have the numbers, that tell what the allowable depth of the pit is that could be repaired, which can't be repaired,

 

1001

 

but in any case, where the sealing surfaces are repaired, the contractual requirement on Thiokol is that they still have to remain within the specification limits.

Now, this is the spec limit for this dimension, 144.373 plus or minus .004. You can see where 51-L was. You can see that if for any reason that segment had to be repaired, it could be repaired, but it could never violate that dimension, even after repair.

The other dimensions of interest are dimension A, which is specified as a minimum, although there is a maximum, too. That is the tang width of 51-L dimension was .789. The spec allowable is - this should be reversed - is .792 to .777. The other dimensions of interest is the gap of the clevis on 51-L that was .841. The spec allowable - and this should be reversed, too, is .842 to .827. You can see that this was on the high side within spec, and this, of course, was just about, I guess, close to the middle of spec.

Some other dimensions of importance is the O-ring groove width, and that is .310 to .305 max. The other is this O-ring groove depth, and that is .216 to .209. 51-L was .211. And when I say 51-L, I am talking about 51-L aft field joints specifically.

The other dimension which was specified was -

 

1002

 

s this gap here between the outer leg - that is, the gap between the outer leg of the clevis and the tang, and that is specified at .032, and that is controlled by the thickness of the shim.

Remember, we said in every case after the pin is put in, around each pin is put a shim. So that is a well controlled dimension.

So then in the use of these dimensions, one calculates a maximum gap, and in the case of 51-L, that static gap was .020.

Now, let me just make one other point, and then if anyone cares to pursue the details of this, there is an actual formula that is used to calculate that. Let me just mention one other thing, that unpressurized, the calculations are made for a gap size, a minimum sealing gap size and a maximum sealing gap size. The calculations are made assuming that the tang portion is not concentric. In other words, it assumes that on one edge I am up against this leg here, and the only thing I have got separating me is .032, and then all the rest of the dimension can gather such as the other side, is the maximum opening.

So that assumes that that piece is eggshelled to the maximum extent possible to give you the maximum gap possible with the dimension that you have here.

 

1003

 

The 51-L O-ring squeeze - and this assumed a minimum O-ring diameter - the O-ring is specified .280 minus .003/plus .005, and we assumed in all of our analysis and calculations on 51-L that it was minimum O-ring size, .277, but the static squeeze at room temperature for the O-rings for 51-L was .0395, and that is 14.7 percent, and calculated at 26 degrees Fahrenheit, which accounts for shrinkage of the O-ring, it was .0356, or 13.4 percent squeeze.

Now, the minimum spec squeeze allowed is 7.54 percent. I would only point out that 51-L, in terms of actual dimensions, aft field joint, would be somewhere I would say in the average dimensions that we could stack up on these things or slightly better than average.

Could I have the next viewgraph, please?

DR. COVERT: Wait a minute. Stop, please.

[530] MR. SUTTER: Have you ever measured these dimensions when you put, say, the flight loads on it or put torsion and bending on it?

MR. HARDY: Yes. Go back to that viewgraph, please. It is not shown here, but remember the leak check port that goes through here? In the structural, static structural load test that we ran, and also in the hydroproof test, each one of these segments is hydroproofed to about 10 percent or 5 percent, I believe, it is at maximum expected operating

 

1004

 

pressure, we have on a number of those units taken that plug out because it didn't enter into the test that we were running, and put a dial plunger, a little device that has got a spring-loaded plunger that rests up against this leg here, and we zeroed that condition in, the static condition, and then as we brought pressure up to the ignition transient, up to max pressure, we measured the increase in that gap. We plan to do some more of that. We want to - well, first of all, let me say that what that does is measure the deflection of this joint as a result of the pressure load, and that is essentially a line load that is pulling through the bulkhead on that end, and it is pulling through the bulkhead on that end because the joint is tending to, or this clevis is tending to rotate around where the pin would be here, and that puts forces this way and this way to tend to spread it.

We have also done testing in the static structural test program where we had the two segments joined together in the test facility, and we pressurized those segments, and then we applied at this point here the bending load and the loads at the back side here, the design loads, and then we measured the deflections of the joint the same way, and we also, of course, measured and sealed any leak if we had any, and I might say that

 

1005

 

in that test program, which went over a number of months, the joint was pressurized, I can't remember how many times, but I'm going to say in the tens if not in fact a hundred cycles, and we never changed the O-rings. We left the O-rings in there.

So that is not, of course, the way we fly. We change the O-rings after every flight, but the O-rings are rather tenacious to cyclic loading.

Now, we are not satisfied totally today with the data that we have in hand, so in the pursuit of this failure analysis, we are continuing to measure this deflection or have a test program to measure this deflection where we are going to go around at eight different locations and we are going to drill seven more holes to correspond with the one hole where we have

and put eight gauges in there, and measure it circumferentially.

 

1006

 

the pressure port,

DR. FEYNMAN: I believe we have seen some pictures that were shown to us of the gap changing from .042 to something like .061. Is that what we were talking about?

MR. HARDY: .042 to .061, yes.

DR. FEYNMAN: Is that a result of those experiments you're going to try to repeat?

MR. HARDY: Yes.

DR. FEYNMAN: What does that mean? When I look at these numbers here, what would that mean when the pressure is put on the gap increased by what - excuse me, decreased by what, et cetera? How do I use those numbers?

DR. HARDY: I will show you that on the next viewgraph.

DR. COVERT: Before we do that, George, I was going to ask: How much does the change in the inner radius, when you take the temperature of this thing and drop it from say 70 degrees down to 25 degrees?

[531] MR. HARDY: That calculation has been made, but I don't remember it, Gene. I don't have a recollection. You're talking about the basic shrinkage from temperature?

DR. COVERT: Right.

MR. HARDY: Of course both sides are going to

 

1007

 

shrink some. There may be a differential there.

DR. COVERT: One side goes into compression, the other side gets stretched.

MR. ACHESON: Can we assume that when you stack the two segments, that it is really impossible to push the O-rings out of the groove by some accident? And even if you did, it would probably just produce a tighter seal?

MR. HARDY: Yes. Could you go back to the viewgraph on the right, please? I have to have that viewgraph to show that.

(Viewgraph.)

If you notice, and I don't know if this would show too well or not here, but the O-rings are in the groove here, and you will notice that the tang is designed so that this portion of the tang can pass the O-ring without any engagement, and in fact this tapered surface here will contact here (indicating) before anything gets to the sealing surfaces. And it's designed such that as this taper here rides in on this taper to avoid any scrape across the O-ring, now I wouldn't say that couldn't happen, because if in fact you had an O-ring that was not pushed back in the groove, that could possibly happen to you. You could in fact engage the O-ring and damage it.

 

1008

 

MR. RUMMEL: Doesn't that assume perfectly concentric mating? Why can't that be a little bit off center so that in fact you, through the holes, take the pins? Why wouldn't you have a possibility of shearing part of the O-rings? And as it slides in, if it slides in metal to metal, if it isn't exactly concentric - -

MR. HARDY: I see what you're saying. You're saying it is not concentric, and this does come into where it comes in right here.

MR. RUMMEL: It would be a masterful job to hold anything this big perfectly concentric.

MR. HARDY: If I could, I would like to defer the answer to that question to the presentation that is planned for you on the mating of this joint. That is in fact the primary reason that it is necessary, when mating, when I've got this segment, if you rotate that 90 degrees and I've got this segment on a crane, and I'm lowering it into position where I can go into this crevice here, the procedure requires that that be halted at some point there, and reference dimensions be made to ensure that it is round enough that that is not going to occur. But the details of that will be explained to you tomorrow, and I would like to defer that, if I could.

If I can answer another question, I would be

 

1009

 

happy to do it, but I think you are going to actually see a demonstration.

MR. RUMMEL: The only question would be that if indeed there was a metal-to-metal slide, then theoretically you could in fact pare the O-ring at that point. Is that correct?

MR. HARDY: That is correct. Could I have the next viewgraph, please?

(Viewgraph. ) [Ref. 2/13-54]

MR. WAITE: Have you ever done any pressure checks, and then pulled them apart and had an O-ring cut as a result of this?

MR. HARDY: I believe there has been some experience of what's referred to as nibbling, or damage, and I'm not speaking here at Kennedy. I don't know that they have disassembled - well, [532] they have disassembled some, too. But at Thiokol in the test programs there have been some occasions where they have taken them apart after they've been assembled, and they see some nibbling, or damage, on the O-rings.

Now that has been - and then there's a big question: Did that happen when I put them together? Did that happen when I took them apart?

MR. WAITE: But they did pass pressure checks?

MR. HARDY: They did pass pressure checks,

 

1010

 

yes. If I could, I would just like to explain a little bit of the dynamics of this seal, and I will relate it first of all to the generic type description of how the seal operates, and then I will give you some information, albeit preliminary, because we are still trying to refine the analysis on 51-L.

This picture here represents step one, and that is at time zero, pressure zero, and that is a static condition. The primary O-ring is somewhat exaggerated here, but it is back against this side of the groove.

[Ref. 2/13-55]

The second area O-ring is against this side of the groove, and that is because of the pressure test that I mentioned earlier. We put 200 psi in there.

DR. FEYNMAN: When you put the 200 psi, do you often have some leakage temporarily, at least, through the primary? Do you make bubbles in the putty?

MR. HARDY: I can't recall any cases recently. There may be some in the early test program when we assembled these horizontally. We had a few more problems with them, as you can imagine, and we have had to take some segments apart. When they were assembled on the test stand, they are tested horizontally, and we have been unable to pass a leak test, and had to take them apart and put them back together.

 

1011

 

But in any case, the flow starts across here. The first step is that this O-ring starts what we call pressure actuating, or moving toward the other side. Now the distance, you recall, that I told you that it could be depending upon dimensions could be 15/ to 30/1000, roughly. I'm going to talk about the gap here in a few minutes.

As flow continues, this O-ring moves completely to this side. And then, as the pressure builds up, it actually forms what we refer to as an extrusion seal. Now this is an exaggeration here a little bit. I don't think it goes to a square in that corner, but we do believe that there is a slight dimpling, if you will, of this O-ring into that gap.

Now that makes the gap very important.

DR. COVERT: George, is that edge of the O-ring groove broken? Or is that a fairly sharp - MR. HARDY: It has a radius on it, and I don't remember the dimensions.

DR. COVERT: The important thing is it is not square.

MR. HARDY: We ran some tests, for instance I think it might be of interest here, on whether or not we stretch, rupture the O-ring, and we run tests pressurizing these O-rings up to 3000 psi, and we use

 

1012

 

them in the neighborhood of 900 and 950 psi. And also we have done that at various temperatures. And we also have, as I mentioned in the structural test article, recycled the O-rings around 1000 psi for 50, 60, 70, 80 times.

DR. FEYNMAN: Again, when the ring is moving because of the flow and hasn't finally set in, is there some chance of a little bit of leak? The reason I ask this is because Mr. Weeks [533] noticed that the motion in the nozzle ring is 110, and not just 15/1OOOths of an inch, which is much more. And he was trying to account for the fact that the nozzle has more blow-by, almost 10 times, as the field joints, and I wondered what your opinion was, whether the actual fact that you have to move it further would weaken possibly the seal and account for the difference between the nozzle and the field joints?

MR. HARDY: The nozzle joint is different, as you know, than other joints. It's a great deal stiffer. But I do believe that the fact that the nozzle joint primary seal groove is wider by several thousandths and the fact that when you pressure actuate the seal and have to move it over a greater distance does account for the somewhat higher occasion of blow-by in the nozzle joint.

 

1013

 

But in any case, these are the steps. Now the design is such that if for some reason this fails to seal, then the secondary O-ring should take the pressure and essentially form the same type of O-ring or the same type of seal.

Now critical in this process is the rate of application of pressure, the squeeze on the O-ring and the change in the gap here. I would like to point out the fact that I believe the squeeze on the O-ring is important. To maintain pressure behind the O-ring while it is pressure-actuating, the gap dimension is important in the ability to form the extrusion seal and maintain that.

Now the dynamics of this seal is very important to us in the failure investigation, and we have a number of tests structured for this, and I will talk about them in just a few minutes. But a preliminary analysis as to what's happening in the squeeze on the O-ring and what is happening to the gap on 51-L dimensions, that is from the time we started at static zero pressure, static zero time, which is down here in this corner (indicating), until we build up in pressure with time, what is this gap doing? And also, what would be the effect of temperature on that sealing, little sealing dynamics?

 

1014

 

Well, the effect of temperature is still in analysis and will be subject to tests. We believe we have to actually run the dynamic tests. But just to look at some of the things that are not affected, as is for instance the O-ring by temperature, as the pressure goes up - and I've plotted here 10 milliseconds. In fact, the pressure is about 25 psi.

At 80 milliseconds, it's around 60 psi. And then at 150 milliseconds, it essentially hasn't gone up. What happens there is that the igniter in the head end of the motor provides the first initialization or pressure vise, and then as the crane ignites and the pressure starts going up, then the pressure starts going up very fast. But the deflection, if you will, and the gap change is represented by this curve.

So at 200 milliseconds, I'm at 250 psi and the gap is changing approximately 4/1OOOths. Now what's important to understand is the seal performance under those dynamic conditions, and in the temperature area of interest.

So we have a number of tests designed to evaluate the performance of the O-ring under temperature-pressure dynamic conditions. These tests, some of them will be scale tests. Some of them will be portions or representative of full-scale tests. We will

 

1015

 

be taking the joint down to ensure that we have the O-rings at the temperatures predicted that 51-L would be. We will set up the initial conditions like we had on 51-L, and we will apply the pressure to the appropriate pressure profile.

Our objective is to see do we get blow by the primary O-ring, and if we do, will the secondary O-ring seal under those conditions?

[534] MR. SUTTER: On that curve, I don't know whether you carried it out to, what, 800 seconds?

MR. HARDY: To 600 milliseconds.

MR. SUTTER: What is 600 milliseconds?

MR. HARDY: 6/1Oths of a second.

MR. SUTTER: That says that the squeeze goes from .038 and drops down to .018? Am I reading the chart right?

MR. HARDY: That would say at 600 milliseconds the gap, the delta, the gap is 20/1OOOths. And if I started with a 36/1OOOths squeeze, and I had immediate response of the O-ring to fill the gap as it opens up, I still have a 16 mil squeeze.

But what is of interest to us is how will the O-ring respond at reduced temperatures.

MR. SUTTER: So the O-ring could be sitting there with very, very little squeeze on it and its

 

1016

 

performance has got to be a lot lower.

MR. HARDY: I would just change your words a little bit. The O-ring is going to be sitting there with the gap opened, and its response to the gap opening, its resiliency could be hampered by temperature.

GEN. KUTYNA: If you had zero resiliency, it wouldn't spring back at all. You could have a gap as much as 20/1OOOths.

MR. HARDY: At this time, that is correct. Now unless something else has happened, unless something else has happened, I am long overdue for actuating the seal. Now this happens here at about 25 psi, 25 to 50 psi. This happens at 100 to 150 psi. And so at 600 milliseconds, I am at 700 psi plus. So the seal should actuate. Nominally the seal should actuate in this timeframe down here.

GEN. KUTYNA: Let me ask you, do you start time at the time that you light the solids, 7 seconds prior to that? Or is it 7 seconds when you light the liquids?

MR. HARDY: Right.

GEN. KUTYNA: And you go through an excursion of the bending moments on that chart, even though it is not very bad, what happens to that gap as a function of those bending moments in those 7 seconds?

MR. HARDY: I cannot quantify that. I can

 

1017

 

tell you that the dynamic model shows - the gap opening characteristics shows that the vast majority of the load that causes that gap to open is the pressure load. Now the bending load does have an effect on it.

GEN. KUTYNA: Are you going to run a test?

MR. HARDY: Yes. We're going to run a test, and we're also including in our model the effects of bending, and we will in fact incorporate that in the gap opening at these various times.

DR. FEYNMAN: So a preliminary estimate or kind of a guess when thinking about it, which way the gap goes at the initial bending, whether it's on the back there, does it close down first and then open on account of the pressure? Or does it open on account of the bending and then open still further?

MR. HARDY: It would tend to close, compress in this area, and open over here. Now again, our area of interest is maybe somewhere in between the compression and the tension. It is closer to the compressive load than it is the tensile load.

MR. ACHESON: What does the gap curve look like in other flights?

MR. HARDY: This would be - and I can be more specific with the data - but this would be near nominal, or I would say a little better than average.

 

[535] 1018

 

MR. ACHESON: Why does it drop back there at 80?

MR. HARDY: Well, of course the gap primary response is to the pressure. The highest pressure we see here is really the igniter. The igniter in this motor is about the size of the third stage of a Minuteman. So it is a big igniter. And that pressure causes the initial rise right here, and then the main grain ignites, and then it catches about here, and then it shoots it straight up.

VICE CHAIRMAN ARMSTRONG: Did I understand correctly the pressure measurements on that graph come from the transducer, and that the gap comes from calculations?

MR. HARDY: That is correct. The gap measurements come from actual measurements made in the pressure test that I referred to, and they also in that analysis we used strain measurements that we put on. In static firings, we put strain measurements around these various joints. So we know the strain that is going in just from the pressure around each one of these joints. But the gap is calculated based upon actual dimensions, and the model which has been validated by actual tests that we ran.

MR. RUMMEL: Did those calculations assume

 

1019

 

perfectly concentric mating of the components?

MR. HARDY: No. They assume the worst case that you could get, nonconcentric worst case that you could get. And let me explain that one more time.

That says that I've got two circles here, or I've got a circle nonconcentric, and then I've got another circle nonconcentric, and I put - at one point I put those just as close as I can possibly get them so that at another point I've got them as far away as I can have them, and that is what is referred to as the max gap.

MR. SUTTER: Could I ask one more quick question? A vendor can change these O-rings, or change materials? Has there been any change in the manufacturing process? Has anybody checked those records?

MR. HARDY: The primary vendor, as I mentioned, Parker-Hannafin, molds them and Hydropack that cuts them measures them, dimensionalizes them, and fuses them together, has not been changed to my knowledge. We have not changed the vendor for the rubber, although there are two sources, and we are in the process right now - and some way along on this - tracking back to the ore in the mine. We're tracking back to the rubber, the batch of rubber that was

 

1020

 

manufactured for these very O-rings that went into 51-L, what the chemical analysis and constituency of that rubber is. We are comparing. We're looking to see where else in the program it was used, if it has ever been used before.

We're doing the same thing by O-ring lots. So we are going back to the origin of the rubber to make that distinction.

MR. SUTTER: These O-rings that are checked out at Thiokol and put in bags, are they serialized so a given O-ring goes into a given segment? Or are they just in a store and you take out so many of them out of storage?

MR. HARDY: I'm not positive of that. Horace, do you know?

MR. LAMBERTH: I'm not positive of that, George. I will check.

CHAIRMAN ROGERS: George, just in consideration of our reporter, maybe you ought to pause a little bit. It's pretty rough for him. It's been a long session. Why don't we take just a few minutes break.

[536] (Recess. )

MR. HARDY: Mr. Chairman, if I might proceed, I think I have maybe one more chart here and I will be

 

1021

 

finished my presentation. I would like to just mention one thing to make sure that I gave a correct answer, or you have a correct understanding regarding the inspection and certification of the O-rings that is done at Thiokol and delivered here certified.

It is, however, at Thiokol that government inspection is mandatory on the inspection of those O-rings, so it is done by Thiokol and government inspection. I just wanted to make sure. I thought I made that clear, but I wanted to make sure.

The only other thing I want to make clear before I go to the last chart, and then I will conclude, is with respect to the launch environment, cold temperatures. In addition to the effects of temperatures on the O-rings and the O-ring response and sealing performance capability, we are also running some tests and some analysis to see if it is possible that water in the joint creasing could in any way upset or effect this secondary sealant capability.

If you go around the joint here in the crevice, the water would be in this area here (indicating), and we are doing the analysis and tests to determine if there would be any effect of ice in the joint affecting the sealing capability. If I could go to the next chart, which I believe is my last one.

 

1022

 

(Viewgraph. ) [Ref. 2/13-56]

This is proceeding on with the scenario that said that after primary O-ring blow-by, either the secondary seal leaked or because it was defective, or because it was affected by the temperature, or because it had ice in the joint, or whatever reason, or the leak checkport leaked, then the next event that occurs is at 58 seconds, approximately, where we know we have leakage out of the aft field joint.

These two events show up in every scenario because they in fact happened. So in every case we have to get back to this event. Now as mentioned before, and I won't belabor it anymore, we are experiencing analytically a great deal of difficulty sustaining a leak from at liftoff, or near liftoff, through the joint, the primary and secondary O-ring, and having it wait until 58 seconds before it shows itself as a blowing leak.

In fact, if we do the simplistic analysis and just simply assume that the entire joint by dimension has the complete ability to vent - that is, there is no choke points, no flow blockage or anything like that, it would indicate that we would be leaking profusely all the way around that joint in about 12 to 15 seconds.

Now we do know that there would be flow

 

1023

 

blockage in certain areas. It could be upstream, it could be downstream. So we are refining that analysis. But there is difficulty in maintaining the picture that we see and that is, let me say, a limited leak at best for 58 seconds, which grows into a bigger leak for that period of time, to the thermal flow analysis. But we are continuing to analyze that.

The next question would be the structural capability of that joint, and the structural capability of the joint assuming maximum flow conditions through there would also be degraded to the point that we would question the ability for the continuous leak. Emphasize again, those analyses have to be refined.

[537] We have to run some tests to more properly characterize the flow conditions and complete those. That does not of course attack a scenario like this, because a small leak through this port could wait until about 58 seconds to manifest itself in the secondary O-ring, nor does it attack the scenario that says I've got limited leakage for some number of seconds, and I won't try to quantify that right now.

I did damage to the primary and secondary O-ring, but it sealed. And then when I came to max Q and got the maximum deflections on the joint, the degraded seal could not hold the seal. And so we are

 

1024

 

studying all of those scenarios.

I just wanted to tell you at this point at least, in a scenario that said that we started a leak through the primary and second O-ring at ignition, and that leak continued for 58 seconds is difficult to control it the way the photograph tells us it must have been controlled up to that time. But that doesn't rule out all of the possible scenarios for that event.

And I think that just about brings me to the end, except to say that in many of these scenarios that I've talked about here, particularly those that have to do with the joint dynamics, the sealing characteristics, the dynamic effect of transverse loads, et cetera, is a fairly comprehensive test program that we have got set up and in process.

Some of these tests will be conducted in Huntsville. Some will be conducted in Utah, and some will utilize test fixtures that have been in place. Some are requiring special test fixtures that are in fabrication now. We will be starting tests, and in fact are scheduled to start some of those tests at the end of this week, or just about in the now timeframe, and I expect they will be going on for the next two weeks, two or three weeks. And most of these tests are subscale tests, or component level tests. And as we learn from

 

1025

 

those tests, a need to get to a higher fidelity, and maybe even a full scale, we will define those tests as we proceed.

But the objective of those tests is to test these scenarios for any event they're in, and either credit it or discredit it, prove it or refute it. One other thing, as we continue and particularly in the area of dynamics and loads, we will develop any appropriate new scenarios. We will change the scenarios as they may have to be changed, and we will interconnect them, if that is indicated.

That concludes what I had prepared.

CHAIRMAN ROGERS: Thank you very much. May we go off the record for a moment?

(Discussion off the record.)

CHAIRMAN ROGERS: Let's go back on the record.

DR. WALKER: I had one question on the last presentation. Could someone say something more about the infrared picture evidence?

MR. HARDY: If I could, I would like to call on our thermal analyst who is with us from Marshall, and he has been working with the PSC people over the last several days to try to get some understanding or resolution of the difference between this and the metals at issue.

 

 


[Please note that some of the titles to the references listed below do not appear in the original text. Titles are included to identify and clarify the linked references - Chris Gamble, html editor]
[
538] [Ref. 2/13-32] 51-L FAILURE ANALYSIS STATUS REPORT. [Ref. 2/13-33] 51-L FAILURE ANALYSIS STATUS REPORT.

[539] [Ref. 2/13-34] 51-L FAILURE ANALYSIS STATUS REPORT- Failure Scenarios.

[540] [Ref. 2/13-35] 51-L FAILURE ANALYSIS STATUS REPORT- Failure scenario 4 (A)- External tank hydrogen leak (first event).

[541] [Ref. 2/13-36] 51-L FAILURE ANALYSIS STATUS REPORT- Failure scenario (A)- External tank hydrogen leak (first event). Event (A1)- LH2 burns and overheats right hand SRM aft field joint.

[542] [Ref. 2/13-37] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario (A)- External tank hydrogen leak (first event). Event (A3)- Overheated O-rings fail in right hand SRM aft field joint.

[543] [Ref. 2/13-38] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario (A)- External tank hydrogen leak (first event). Event (A2) - LH2 cools right hand SRM aft field joint. [Ref. 2/13-39] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario 4 (A)- External tank hydrogen leak (first event). Event (A4) - Joint overcooled and O-rings fail.

[544] [Ref. 2/13-40] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario 4 (A)- External tank hydrogen leak (first event). Event (A5) - SRM hot gas impingement on att. struts and ET. [Ref. 2/13-41] 51-L FAILURE ANALYSIS STATUS REPORT- Failure scenario (B) - R.H. SRM AFT FIELD JOINT LEAK (FIRST EVENT).

[545] [Ref. 2/13-42] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario (B) - R.H. SRM AFT FIELD JOINT LEAK (FIRST EVENT). Event (B) - Primary O-ring blow-by.

[546] [Ref. 2/13-43] AFT SEGMENT/AFT CENTER SEGMENT FIELD JOINT CONFIGURATION.

[547] [Ref. 2/13-44] 51-L FAILURE ANALYSIS STATUS REPORT- History of Primary O-Ring Damage on Field Joints.

[548] [Ref. 2/13-45] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario (B) - R.H. SRM AFT FIELD JOINT LEAK (FIRST EVENT). Event (B2) - Leak check port leaks.

[549] [Ref. 2/13-46] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario (B) - R.H. SRM AFT FIELD JOINT LEAK (FIRST EVENT). Event (B1) - Secondary O-ring leaks.

[550] [Ref. 2/13-47] [photo of a clevis]

[551] [Ref. 2/13-48] [photo of a clevis]

[552] [Ref. 2/13-49] SRB AFT SEGMENT PRELAUNCH - COLD CASE MOTOR CASE TEMPERATURES.

[553] [Ref. 2/13-50] PRE-LAUNCH THERMAL PREDICTIONS. [Ref. 2/13-51] STS 51-C SRB AFT SEGMENT PRELAUNCH - COLD CASE. CASE AND PROPELLANT AVERAGES.

[554] [Ref. 2/13-52] SRB AFT SEGMENT PRELAUNCH - COLD CASE. CASE AND PROPELLANT AVERAGES.

[555] [Ref. 2/13-53] 51-L R.H. SRM AFT FIELD JOINT (NTS).

[556] [Ref. 2/13-54 and 55] 51-L FAILURE ANALYSIS STATUS REPORT- JOINT O-RING SEAL PERFORMANCE CHARACTERISTICS.

[557] [Ref. 2/13-56] 51-L FAILURE ANALYSIS STATUS REPORT - Failure scenario (B) - R.H. SRM AFT FIELD JOINT LEAK (FIRST EVENT). Event (B3)- Major leak at right hand SRM aft field joint.


 

[558] MR. BACHTOL: Rick Bachtol from Marshall. As George presented the minimum temperature we predicted on the SRB was on the order of 21 degrees, and that was a cold case. That is where we assumed the coldest sky, a minimum wind, et cetera, to try to see if we could get down [559] to the measurements that were being made on the pad. Now what was made on the pad was 9 degrees on the right-hand SRB.

We estimated there was a 4 or 5 degree error in that.

DR. FEYNMAN: Which way?

MR. BACHTOL: Well, I mean the measurement was too low by 4 or 5 degrees. And the problem there is, as the gentleman was shooting up at the SRB, the night sky was reflecting off of the SRB. The SRB is about .85 incidents, and we went out this morning and made some tests, and it looks like that error may be as much as 6 to 9 degrees, and the reason being it is a little more is because the instrument is only sensitive in the 8 to 12 micron region by design. That is also a window in the atmosphere as far as water vapor is concerned, so the night sky looks a lot colder to the instrument than it really is.

So we estimate there's about a 6 to 9 degree error on the low side, and a 9 degree heat measurement

 

1027

 

which gets it up to 15 to 18 degrees. And so we still have a small discrepancy between the 18 that he measured, and we put that 9 degree error on it in the 3 degrees that we calculated, and we're still looking at that to see if we can resolve that. But that is where we stand right now.

DR. COVERT: Why is there a difference between the right and the left side?

MR. BACHTOL: Well, the right-hand side has a good view of the night sky, so we would predict it is colder. The left-hand side, when he is shooting up at it, he is reflecting the -

DR. COVERT: It is because of where he is standing?

MR. BACHTOL: Right. And he is reflecting the fixed surface structure, and we have proved that this morning when we were out there.

DR. COVERT: I am touched by your faith in your model, and I guess my experience with these things are such that - well, in what way have you calibrated this thing down at these kind of temperatures.

MR. BACHTOL: Let me say the model probably has, as far as surface temperature is concerned, plus or minus 4 or 5 degree error, but what I have done is biased down so that I feel like I've got pretty much

 

1028

 

minus zero. So I have oriented everything toward the low end to try to see how cold I can really get. For example, I assume the sky in my model was minus 30 degrees, which is a lot colder than a lot of people would think.

DR. COVERT: But still and all, have you ever really honest to God validated your model at temperatures at say below 30?

MR. BACHTOL: Well, for example, the day before we were within 2 degrees.

DR. COVERT: What was the temperature the day before?

MR. BACHTOL: The SRB temperatures were in the 30s.

DR. COVERT: So you're in a sense trying to validate the model and use it at the same time? Good luck.

(Laughter.)

MR. CRIPPEN: I guess I would like to make one point. Even though we're still trying to understand those measurements, this was the first time that we had ever seen that kind of a difference between the left and right-hand SRB.

MR. BACHTOL: That's true. We've never seen that before.

 

[560] 1029

 

DR. COVERT: In the future, will you have him walk around and look at it?

DR. WALKER: So these measurements usually agree fairly well with the model?

MR. BACHTOL: They usually agree with the model in the right and lefthand SRB. They usually agree with each other unless one of them happens to be in the sun.

DR. FEYNMAN: Of course the primary question is not whether it agrees with the model or not. The primary question is whether what the temperature is that you measured, that is to say, what is wrong with the instrument, if I may put it that way, or how much specular reflection from the sky is going to produce, you mentioned 6 degrees. Is that figure also pushed for some reason, assuming the night sky is colder than you would have ordinarily thought?

MR. BACHTOL: No.

DR. FEYNMAN: To the normal night sky and normal reflection, not trying to push that?

MR. BACHTOL: This morning we demonstrated a 6 to 9 degree error, and you are right. We were interested, we are interested in the measurement. Because if I can only predict 21, and we actually had 9 degrees on the pad, then there is something else that is

 

1030

 

causing it that we have to look for.

DR. FEYNMAN: When you're pushing, you should push on your model, but you shouldn't push on the instrument.

MR. BACHTOL: That is why we went out and ran the test.

CHAIRMAN ROGERS: Okay, if we may now to go Mr. Moser.

MR. MOORE: He will talk about some work he has been doing on the failure scenario team.

 

[561] 1031

 

STATEMENT OF T. MOSER, HEAD, FAILURE SCENARIO TEAM, JOHNSON SPACE CENTER

 

MR. MOSER: I am going to talk to you this evening primarily about the failure scenario teamwork that we have had going on at Johnson Space Center.

(Viewgraph. ) [Ref. 2/13-57]

There is a bit of other work that I want to review with you briefly. It is, and you can think of this entire report as a status report, and in light of what you just discussed about releasing information, I think it is true of everything I will show you here. We have tried to show you in a status everything that we know to date, and a lot of it is very preliminary, but it is our best shot today of the way we see things, and it can change.

So I will point that out now, and I will point that out as we go through some of the analyses that are being refined, and we will continue to do that. So I think the entire system needs to recognize that. If I could have the next charts, please.

(Viewgraph. ) [Ref. 2/13-58]

A little bit of background. What we did at the Johnson Space Center from the day, the morning of the incident, we formed a team that was consistent with

 

1032

 

our contingency plan at Johnson Space Center, signed by the Director also. It was comprised primarily of program and project office personnel in addition to discipline experts throughout the center, and in addition to a staff. It was formed as you see here.

The purpose of this organization was to, number one, ensure that we captured all the data. We are controlling that. We established a focus for this team, shown up here as a MER. That is our Mission Evaluation Room, which is an engineering focus for all of our activities in support of shuttle missions. All of our technical information flows through this in support of Mission Control Center. That was our focus for this activity.

We had developed an investigation plan for each one of the teams. We had established a time line, which you have seen, by Mr. Kohrs today. That is a dynamic time line that is changing as we interpret the data, I might add. And then we have daily tankups to exchange information between us.

The failure scenario team, which I am currently heading, was formed several days afterwards, once we began to get the data. To date, here is a one-page summary of what all of those other team efforts are, other than the failure scenario team. We have gone

 

1033

 

through all of the orbiter systems. We have gone through the main propulsion system - and by the main propulsion system, I mean the engines, the lines in the orbiter up to the interface between the orbiter and the external tank.

[562] We have looked at the cargo, and the environments associated with the flights, both the natural and the self-induced environments; the dynamic loads; the thermal effects during ascent. We did not - we have let Marshall do primarily the work on the temperatures on the pad.

We do not see any indications at this time of any one of these systems contributing to this incident. We have not concluded our work there, however. We are spending most of our team efforts right now on an ascent reconstruction of the loads in those environments, and that is quite an extensive effort.

For that, the Johnson Space Center is responsible to the total system to define the loads, the vibration, the thermal effects on this entire stack configuration of all the elements. If I might take a moment, what we do for this particular configuration, we are going back and looking at the predicted thrust as measured from the solid rocket boosters, the mass properties of the system.

 

1034

 

We are doing a complete dynamic multiple response of the systems so we get the dynamic loads, we get the static loads, and we combine all of those so that we will provide to Marshall for their detailed structural analysis of this joint, or anything else that they want to analyze, an overall complete compatible set of dynamic loads. That is a significant amount of the work.

It will be using as best predicted winds at the time of the event. We have talked about max Q alpha, the dynamic pressure versus the angle of attack of the vehicle as measured as predicted. We will be filtering all of - or factoring all of that into these loads.

GEN. KUTYNA: Without extending the evening, much of the team has not seen the twang the Shuttle does on liftoff. Could we get a quick movie of that tomorrow? It takes about 15, 20 seconds. Have you got a good illustrative one?

MR. MOSER: I would say yes, but I can't speak for Kennedy. I know it is on every flight. All we've got to do is find the right camera. Looking primarily from this angle, you can really get the response. We are continuing with the major focus of our effort to the failure scenario team, and I'm going to spend most of

 

1035

 

this afternoon in my discussion with you on that.

The visual team has an effort and tried to enhance photos. We're doing a lot of work in that area. We're looking at the spectral analysis of the photographs, trying to understand what is causing different things that we see. We are looking at temperatures, trying to use calibrated pyrometers to look at photographs to see if we can get temperatures from that, in addition to the analysis that we're doing.

DR. FEYNMAN: How can you look at a pyrometer with a photograph?

MR. MOSER: We're going to try some schemes we have in our minds to see if we can calibrate.

DR. FEYNMAN: Do you have color photos? Do you have many different filters?

MR. MOSER: Yes. We have to look at it. I don't know if it's possible, but we're going to give it a shot. We're trying to do everything we can.

DR. FEYNMAN: I just wanted to make sure it wasn't utterly impossible.

MR. MOSER: Okay. The next charts, please.

(Viewgraph. ) [Ref. 2/13-59]

Now let me spend some time with you on this bullet here of the failure scenario team. The team is

 

[563] 1036

 

comprised of a group of senior, and I will underline "senior", experts in the areas that you see in that viewgraph. We use that team to focus and guide the activities for the failure scenario team, which is probably several hundred engineers that are doing some of the analyses that I will share with you today.

Our process through this organization is we have taken the output from the orbiter, the main propulsion system, and those things, looked at that, at evidence of what appears to be anomalous, or what conditions could exist which would contribute to a failure scenario much like George Hardy explained to you. And in addition to that data which is being documented at this time - and I might add that we do have - we have provided to Jess Moore and to Arnie Aldrich about a one-inch thick status documentation of the activities of the other teams.

We are using that as our findings. We are using visual data, much the type that you've seen today. In addition to that, we have spent a lot of time looking at other missions, corresponding times of what is occurring during the ascent phase of the mission, comparing apples and apples for those two to help give us clues.

The physical evidence we're just beginning to

 

1037

 

factor into our scenarios, and we are using the timeline bits. From that we have constructed failure scenarios. We have four primary failure scenarios that we are working now. I am going to touch in quite some depth on the one, and just tell you briefly about the other three.

The major part of our effort now is verifying each one of the steps in the failure scenarios, much as Marshall is doing.

DR. FEYNMAN: Is this an independent effort from what they're doing here?

MR. MOSER: Yes. I was just getting ready to say that. We have done this totally independent of Marshall. We met with them last week to begin to exchange information and ideas. We have been passing information back and forth about our failure scenarios, and those activities are independent. We are considering now joining efforts, however, to make sure that we get to the right depth.

I think once we establish some baselines, that would perhaps be prudent in our use of resources in order to try to get more depth, but we haven't done that yet. So everything to date has been independent. So then we close the loop. If we have something here we need back from that team, or more photographic data,

 

1038

 

then we close the loop through that process. And I don't want to belabor the process a whole lot. I'm going to leave this chart up, because this is a failure scenario for an SRB leak, a solid rocket booster leak. We have other failure scenarios where the hydrogen leak has been the ignition source, and oxygen leak being the initiating force, but let me talk to this one to give you some feel for the status of our analysis.

This one, compatible with the timeline event Mr. Kohrs showed you this morning with an SRB leak being observed, had about a little bit less than half a second. The plume from the SRB expands in this theoretical model up to the time about 59 seconds. There is heating in the aft end of the solid rocket booster, and the external tank. There is a hydrogen leak detected, and I will substantiate all of this with more fact momentarily.

The righthand SRB moves with respect to the stack at about 72 seconds mission elapse time. We think then there is an overload at the forward end of the external tank spilling liquid hydrogen [564] and liquid oxygen either by an overload here or some ruptures of the lines, and then we see the explosion.

I am going to walk you through this path and

 

1039

 

not spend a lot of time on these other things. We have closed, we think, some of these are closing out, like the large 17-inch disconnect for the hydrogen or oxygen line. We had that in our model, and we see data now which is not supporting that disconnecting.

The next charts, please.

(Viewgraph. ) [Ref. 2/13-60]

This is the way we have tracked through on our system. We establish a time, an observation, what we are seeing, what the data source is for which the observation is made, a premise which goes with that, and then a task which we identify and track, and then for each one of these tasks we have a detailed task description, a set of products, and a schedule which supports that.

I want to start here with the noticeable drop in the pressure of the righthand solid rocket booster on this screen, and I depicted that. You may not be able to see this because of the equipment here, but mission elapse time is just in excess of 60 seconds. We see the divergence. This is the righthand chamber pressure of the righthand SRB, and for the lefthand SRB up through that flight they had been tracking fairly closely.

DR. FEYNMAN: Just one moment, because you've got the same time of the divergence as they did. Is

 

1040

 

that done independently? Because it doesn't look like you could determine that time. How do you know you shouldn't go further on that?

MR. MOSER: Well, what we have done is we have compared our time lines, and we have tried to merge those. To the extent that - -

DR. FEYNMAN: It's not the absolute time that I'm worried about. It is the fact that you picked that point to say those two curves are diverging. How do you know they don't diverge until later?

MR. MOSER: Pardon me.

DR. FEYNMAN: Let's say they do not diverge until later. You still have some time in which the things are the same distance apart as they were earlier.

MR. MOSER: If I'm interpreting you, there should be a tolerance on the start of the divergence, and that is correct.

DR. FEYNMAN: Well, it's remarkable that you come so close to each other.

MR. MOSER: No, I don't want to mislead you or give you any indication that we have not compared time lines. We did that probably about a week ago, trying to get a normalized and compatible set of time lines where we could reach agreement. And so for the purpose of exchanging data -

DR. FEYNMAN: Carry on.

MR. MOSER: obviously you can look at

 

1041

 

this. That could be interpreted to be several milliseconds, or hundreds of milliseconds probably on either side of that. And to further refine that, we are doing more analysis in this region to see if we can pin it down. On the other hand, I don't know that it is really that critical that we be that accurate for that particular one.

 

[565] 1042

 

We looked at that pressure drop. We have estimated the leak associated with that decaying pressure, assuming that the right hand should be tracking exactly with the left.

The next chart, please.

DR. COVERT: Tom, have you calculated what the thrust would be due to a leak of that size? Does that give you a torque that is compatible?

MR. MOSER: I'm going to touch on that in just a moment, but that is a good question, and the answer to your question is yes, okay.

DR. COVERT: Good.

(Viewgraph. ) [Ref. 2/13-61]

As George Hardy indicated, it is difficult to expand a leak from where we think we see a leak at less than half a second after the SRB ignition up until the time of about 60 seconds, where we can see a visual indication of a leak in that solid rocket booster. We're predicting that that leakage in the solid rocket booster is growing at a very fast rate from 60 seconds and beyond, based upon our analysis and trying to extrapolate back down to the time of ignition.

And when we look at a one-dimensional growth like an O-ring moving circumferentially around a solid rocket booster - and let me call that a one-dimensional increase in area - you get an increasing area about

 

1043

 

like the lower sloped curve I show you up here. If it is an area increase from the square of the dimension, then it's a characteristic slope like you see here.

We're still not meeting that type of increase in area. To us that is telling us that we're not only getting - we're getting more than an ablation increase or melting of the steel, that we are literally losing part of the steel case to meet that type of model.

The next chart, please.

(Viewgraph. ) [Ref. 2/13-62]

That is an effort we are spending an awful lot of time on trying to construct that failure to get some bound of what is happening in this joint, and this would be an upper bound. We have modeled thermally, two-dimensional thermal analysis of this joint, letting the 5700 degree gas go from inside the solid rocket, out the labyrinth path, through the clevis and the tang, to see what temperatures are doing out there with the O-rings removed and with the nominal caps.

DR. COVERT: Where do you get the material properties for this combustion? Is that from the JANAF tables?

MR. MOSER: I'm sorry? Repeat that, please?

DR. COVERT: The combustion products from the chamber that's going out.

 

1044

 

MR. MOSER: What we're doing here is just using the gas temperature. We are not using - -

DR. COVERT: You have to know something like CP and CK and all kinds of grubby things like that.

MR. MOSER: I don't know specifically where our thermal analysts got that. I can find that out.

DR. COVERT: And you have to know what the constituents are.

MR. MOSER: Yes, yes, we have that, and I don't know what the source is, but I will find that out for you. I don't know maybe Jack Lee or George Hardy could answer that. I think we probably relied upon Marshall to provide that to us.

DR. COVERT: Fine.

[566] MR. MOSER: We will find that out for you.

Anyway, after one second of flow-through a path like this, we're seeing isotherms as depicted here: 2,000 degrees, 1,000 degrees. As shown after two seconds of flow - and this is what Dr. Lucas was talking about - we're beginning to see melting, as shown in the cross-hatched regions.

The next chart, please.

(Viewgraph. ) [Ref. 2/13-63]

So our flow area is increasing after 3 seconds, and 12 seconds. After 12 seconds, we would

 

1045

 

show a complete violation of that region, again in a two-dimensional thermal analysis. And this is with the O-rings completely gone.

MR. WALKER: And this is all around the circumference?

MR. MOSER: Well, this is just two dimensional, okay. So just taking that heat over that section, we are doing the three-dimensional analysis right now. So this is the type of thing that we are using to help build our model, how this leak rate is changing versus time.

The next chart, please.

(Viewgraph. ) [Ref. 2/13-64]

Another event that we saw in the time line was an unusual pitch motion of the entire vehicle at about 64 seconds. We looked at several things. One was wind response and, just to get to the bottom line, that appears based upon the reconstruction of the trajectory to be the best explanation of that diameter response.

Everything appears to be normal. You will see some wind activity at that altitude, and the vehicle responded to it, and we think that is in fact what caused that.

We also looked at the plume effect from the SRB to see if that could be a contributor to this.

It

 

1046

 

is not very significant in the overall aerodynamic forces on the vehicle. Nor do we see that it is changing the aerodynamic flow across the vehicle significantly.

We also looked at the possibility that one of the separation motors or all four of the separation motors on the aft end had fired, and if that would result in the motion of the vehicle. It does not, based upon our preliminary analysis to date.

The next chart, please.

VICE CHAIRMAN ARMSTRONG: Excuse me. On that previous one, you said something about the simulate with SSFS?

MR. MOSER: The space shuttle flight simulator.

VICE CHAIRMAN ARMSTRONG: It would seem the time to gather such things as wind shear, thrust degradation, and nozzle motions, and various dynamics, it would be appropriate.

MR. MOSER: That is all in that model, Neil. It is all included.

VICE CHAIRMAN ARMSTRONG: All of the elements you can reasonably include, with the mechanisms you have available?

MR. MOSER: That is correct, and I can't think

 

1047

 

of anything off the top of my head that it doesn't have in it. It is quite detailed.

VICE CHAIRMAN ARMSTRONG: And at what point would you expect to get preliminary results out of that?

MR. MOSER: Well, our preliminary results have been completed. It does not show the vehicle responding according to that.

[567] I would say within the next couple of weeks we will have the final results from that. I can look at a detailed task and give you that specifically. Let's see. Could you put the last - okay, all right, go ahead.

(Viewgraph. ) [Ref. 2/13-65]

The next thing in the ascent that we see is the change in the ullage pressure of the hydrogen tank from measurements. We then tried to determine what the cause of that was. We have looked at thermal analysis of the tank, but before I say that let me show you specifically what I'm talking about again. Again, interpretation of the exact time line, probably measured to the nearest thousandth of a second.

But we see what the characteristics and the repressurization is relative to what it had been up to that point. It is not normal. We're not keeping up with the pressurization of the tank.

GENERAL KUTYNA: But that is after the

 

1048

 

appearance of the flame?

MR. MOSER: That is correct, that is after the appearance of the flame.

GENERAL KUTYNA: Eight seconds or so?

MR. MOSER: About six seconds.

So we looked at that and said, what are the potential causes of that. We've got plume impingement on the external tank itself and on the repressurization lines.

The next chart.

(Viewgraph. ) [Ref. 2/13-66]

DR. KEEL: Do we not have these charts?

MR. MOSER: You do have those charts. What I've done is, any ones you see back up there in the back, and I will mesh them together to let the information flow as easily as I could.

DR. KEEL: Would it be possible, for the benefit of the reporter and the record, to indicate what page number, so that we know what we're referring to in the record.

MR. MOSER: Yes, I believe that I can do that. Let me check my system here. It is marked down here. I am now looking at charts 14, BU-14, and on the right screen or C screen, chart 7.

Okay, I'll try and do that. On screen A we have taken the plume from the SRB

 

1049

 

and impinged it directly on the external tank to see if that could have penetrated the wall of the external tank with different boiling heat transfer coefficients of the liquid hydrogen inside and adjacent to the aluminum wall. We have taken, theoretically taken the insulation, the spray-on foam insulation on the tank, off.

We're looking at a thickness of about four-tenths of an inch in thickness, and with a heat transfer coefficient very high. We are showing peak temperatures of about minus 100 degrees with that plume impinging directly on it.

At a lower heat transfer coefficient from the hydrogen to the skin of the tank, we are showing a peak of about 200 degrees, still well below - -

DR. COVERT: So this raises liquid hydrogen to the inside skin temperature?

MR. MOSER: That is correct.

DR. COVERT: What temperature does nuclear boiling take place in hydrogen?

MR. BACHTOL: Well, we usually plot it versus heat plus.

DR. COVERT: I know that. I want to get to that.

MR. BACHTOL: Well, I can tell you the burnout heat flux in about 10 Btu's per foot squared second.

 

[568] 1050

 

DR. COVERT: But this age of 10,000 then corresponds to what?

MR. BACHTOL: I'm not sure. I suspect that is BTU's per hour. I'm not familiar with this analysis.

DR. COVERT: You say 10 BTU's per square foot per second?

MR. BACHTOL: That's right, burnout heat flux.

MR. MOSER: This assumes boiling. With that analysis - and again, we were trying to bound it. We did not show a penetration of the tank. But we also have analysis proceeding which not only takes the heat, but takes the energy from the aluminum particles which are in the solid propellant and impinges it, to see if we can erode the tank away. We do not have the results of that as of yet. The other thing that we are doing - -

MR. WALKER: There's enough thermal mass in the hydrogen to keep the tank pretty cold?

MR. MOSER: That's right. We've even looked at what it would be doing to change the pressure of the gas which is dissolved back into the liquid, and we do not ever show a pressure increase of significant magnitude there.

Again, this is about one week's worth of analysis, which we began on this scenario. The other

 

1051

 

thing that we're going is trying to look at this decrease in pressure by a structural failure which would be manifested in the form of a buckle in the tank. Even though we are not melting the tank and penetrating that way, there are some fairly high thermal gradients set up and fairly high thermal stresses which could cause local buckling, with the local buckling and a crack forming in the tank and then letting that leak.

The thing that flies in the face of that, though, to see those types of pressure decreases we have to be leaking liquid at about 133 pounds per second, which is about equivalent to what is flowing through the engine. And so we don't think that that model is really going to hold up. Or in a gaseous sense, about a little bit less than one pound per second of gaseous hydrogen, which better fits.

The next chart, please.

(Viewgraph. ) [Ref. 2/13-66]

We looked at the gaseous hydrogen repressurization line with a low heat flux, and we're seeing that wall temperature getting out to about less than 150 degrees. For a higher heat flux - the next chart, please.

(Viewgraph. ) [Ref. 2/13-67]

We're getting high enough temperatures to fail.

 

1052

 

But again, we're trying now to model the plume coming out of the SRB and get a better characterization of what heat flux we're really seeing there. In addition to heat, we're also having to look at erosion of that line. That looks like a very high possibility of the thing that is causing the increase in the pressure of the tank.

The next chart, please.

DR. KEEL: Again, could I make a plea with you, please ask you to give some reference title, or figure number to your charts.

(Viewgraph. ) [Ref. 2/13-68]

MR. MOSER: I'm sorry. I'm now looking at chart BU-16 on screen A, and on screen B BU15, and chart 7 on screen C.

[569] MR. SUTTER: Is all of this work to try to find out why it finally went, after the SRB leak started?

MR. MOSER: Yes, sir, seeing if we can fit all of the data to this scenario, that the SRB truly had started there. Some of this analysis is applicable. However, even if the ET started, if everything doesn't fit the physical evidence that we have, we don't think we have concluded or will have a legitimate understanding of what caused this failure.

MR. SUTTER: It would seem to me if that SRB

 

1053

 

ever leaked, like it could have with what we know, after that it's too late.

MR. MOSER: Yes, sir. I agree with you but today we can't say the SRB leaked for sure.

MR. SUTTER: But this is all a lot of work assuming the SRB leaked.

MR. MOSER: Yes, sir. I don't know any other way to build all of the facts into and to put the pieces of the puzzle together and have a clear picture. If I had a one-piece puzzle I wouldn't have a problem, but I don't.

MR. WAITE: Could you consider some of the structural loads at the bottom attachment, like

MR. MOSER: I'm going to get to that in just a moment.

DR. FEYNMAN: There's no way to make aluminum hydride or something when it gets hot, chemical reactions between the hydrogen and the aluminum?

MR. MOSER: We haven't looked at that. That is on the list to do. We have not considered - gotten any depth in that.

On chart A - now, I'm coming up to your question now. Later into the program, into the flight, we see a divergence in the right-hand solid rocket booster

 

1054

 

compared to the rest of the stack. That is the orbiter on the left hand, and that is depicted on screen A. What's shown here is the pitch rate of the right and the left, and you can see slightly beyond 72 seconds, you see a deviation. The same way with yaw.

The potential explanations for that is the plume effects and also the heating on the aft structural attachments of the external tank to the solid rocket booster down here.

The next chart, please.

(Viewgraphs 17 and 18.) IR'f 2 l:~-4i',l

This is a picture - on screen A I have chart 17, and B is 18, and chart 19 is on screen C.

On screen A, the lower attachment strut is shown in the upper part of this view. The center screen shows a cross-section of it. Pyrotechnic is included in that attachment. We looked at the possibility of that pyrotechnic getting to sufficient temperature to detonate it.

Based upon the thermal analysis that we have conducted so far, we show that pyrotechnic being slightly over 100 degrees. I think that that has been shown to be able to get up to about 420 degrees from 60 seconds before the pyrotechnic would be detonated. And so we went one step further.

 

1055

 

Next chart, please.

(Viewgraphs.) [Ref. 2/13-70 1 of 5] [Ref. 2/13-70 2 of 5]

And so we looked at the load on that link. And on screen C, I now have chart 20, and screen B, I have chart BU-15.

[570] The load in that tank is about 80,000 pounds at the time of the event. It is designed for compression of about 290,000 pounds and tension of about 390,000 pounds. So it is well within the capability.

Next chart, please.

(Viewgraphs 22 and 29.) [Ref. 2/13-70 3 of 5] [Ref. 2/13-70 4 of 5] [Ref. 2/13-70 5 of 5]

However, when we consider the temperature, and on screen A I have chart 23, on B I have chart 22, and C, I have chart 21, for the record. Looking at a thinner section of that same lower link, which has less thermal mass, predicting what the temperature is there and the surfaces are for an exposure of a plume like we are seeing at the solid rocket booster, you can see that we are easily getting up in excess of 2,000 degrees.

Looking at the material properties on screen A of a typical Inconel, somewhere around 1200 degrees the ultimate strength of that material just plummets. So that looks like a feasible failure scenario of what has happened.

Next chart, please.

(Viewgraph B-15.) [Ref. 2/13-70 2 of 5]

To further substantiate that, we looked at if that link fails. So now the right-hand SRB is attached at a forward point and it is allowed to hinge about the aft point. It now has a new hinge line which is skewed to the axis of the solid rocket booster. If that rotates up toward the orbiter, then the ratio of the pitch rates and the yaw rates about an axis of that rotation correspond to exactly what we measured. So that fits the model pretty well.

Next chart, please.

(Viewgraphs 24, 25, 26.) [Ref. 2/13-71 1 of 3] [Ref. 2/13-71 2 of 3] [Ref. 2/13-71 3 of 3]

I have charts 24, 25, and 26 on A, B, and C. With that, with the loads that are on that, on the solid rocket booster at that time, at about 72-1/2 seconds we would be predicting a rotational rate about that hinge line of 40 degrees per second.

Screen B shows pictorially what that view would be, and screen C shows how the SRB moves over and begins to contact the inner tank region on the solid rocket.

DR. COVERT: What was the roll rate that would indicate that?

MR. MOSER: I would have to go back and look at that. Those are yaw rates, the pitch rates that are

 

1057

 

in the handout there, and I can't remember which of those - what that magnitude was. Shall I go back there?

DR. COVERT: Well, this says relative roll rate.

MR. MOSER: That is the roll rate about the new hinge.

DR. COVERT: I understand that. I wondered what the data indicate. I can't put this back into a single thing in my head.

Lets go on, Tom.

MR. MOSER: It is shown on chart BU-16, that shows the right hand has a pitch rate at that time of about minus point - I mean, about .5 degrees positive. And it has a corresponding yaw rate - this is about the body axis now for the right-hand SRB - which changes drastically and goes up, goes from minus about .15 or 1-1/2 up to about 3-1/2 degrees per second. IRer. /l:~-'ix

Next chart, please.

(Viewgraph 28.) [Ref. 2/13-72]

I want to show you what I think is happening up in the forward end, and again just to put the other pieces of the puzzle together.

[571] (Viewgraph 27.) [Ref. 2/13-73]

Now, on screen B I have 28 and on screen C I have 27.

 

1058

 

With a 12 degree rotation about that new hinge line, we bottom out the forward SRB attachment to that on the external tank. So now we're beginning to induce a bending moment in that carry-through structure between the SRB's, which is a load direction for which it was not designed for a very high magnitude, and I don't know that number right off the top of my head.

Next chart, please.

(Viewgraphs 29 and 30.) [Ref. 2/13-74] [Ref. 2/13-75]

What that is doing, it is inducing loads into the inner tank region, which is dumping them into the blocks, wall, and the bulkhead of that, and the same way with the hydrogen tank.

As the SRB continues to rotate - and on screen B, I have 29 and on screen C chart 30 - the aft attachment does not encounter an interference until it has rotated through about 52 degrees. However, by the time it rotates through that angle, the forward end of the solid rocket booster has impinged into the inner tank region a significant amount, as seen in the crosshatch on chart C. And we are completing the analysis now to show what that would do as far as loading up the external tank, both LOX and hydrogen.

Next chart, please.

(Viewgraph. ) [Ref. 2/13-76 1 of 3] [Ref. 2/13-76 2 of 3] [Ref. 2/13-76 3 of 3]

 

1059

 

said?

From a CAD, the way it would appear to be, in screens A, B, and C, charts 31, 32, and 33. The back end of the solid rocket, right hand solid rocket, has moved up toward the elevons, and from the physical evidence that meets the model also, looking at the damage, in talking to the National Transportation Safety Board members today and looking at it myself.

The head-on view of that, you can see with that type of rotation how that right-hand solid rocket booster has gone up and probably contacted the wing for sure plus failed the tank.

CHAIRMAN ROGERS: Is this compatible essentially with what the Aviation Week story

MR. MOSER: I did not read that all the way through.

MR. HOTZ: It's pretty accurate, sure.

MR. RUMMEL: Isn't the impact point on the tank between

MR. HOTZ: I don't think they had any contact with the wing in their story, but they had the rotation.

MR. MOSER: I saw it is USA Today and they referenced the Aviation Week article, and I believe that they did have it - show it going into the inner tank. It is probably the same thing.

 

1060

 

MR. RUMMEL: Could I ask, the impact point of the SRB with the tank is between the oxygen tank and the other tank?

MR. MOSER: Correct.

MR. RUMMEL: Is there any evidence of those tanks in fact failing?

MR. MOSER: Just the visual evidence, yes, sir.

MR. RUMMEL: There is?

MR. MOSER: In the visual evidence, there is a cloud of vapor at this corresponding time coming out on the tank.

CHAIRMAN ROGERS: If we recover the right booster, will the damage to it likely confirm this theory?

[572] right?

MR. MOSER: Yes, sir, I would think so. It should show some damage.

MR. WAITE: How long has this been available to you since the 8th of February, is that

MR. MOSER: Yes, sir, this has.

DR. RIDE: Do the photos show the SRB contacting the tank?

MR. MOSER: Pardon me?

DR. RIDE: Do the photos show the SRB contacting the tank?

 

1061

 

MR. MOSER: The photos, no, not so far. We can't tell that, Sally. We are trying to enhance it to see if we can, but to date you cannot see that it does, at least not in the observations that I have made.

MR. SMITH: But I guess, even though you can't see that, that would agree with the leakage that you're seeing in the topping off of the forward oxygen tank. I think that fits the story.

MR. MOSER: It fits a lot of the physical evidence, the visual evidence.

MR. WILLIAMS: Plus you've got a lot of burning in that area, too.

MR. MOSER: The next charts, please.

(Viewgraph. ) [Ref. 2/13-77]

MR. MOSER: I'm not going to walk you through the same detail on this, but it is a scenario not too unlike George Hardy showed you. Assuming a hydrogen leak initially, on screen A, which is chart BU-5, 6, and 7, respectively, A, B, and C; which on screen B is an oxygen leak, following through that failure scenario tree; and then a structural failure on BU-7.

And I do not think that I have sufficient information to really show you the status of that today, but we are working that and we will continue to work it until we have closed out what we think is the most

 

1062

 

probable.

And that's it, Mr. Chairman.

CHAIRMAN ROGERS: Thank you very much.

Are there any questions?

(No response.)

Well, I guess we should adjourn for the day if there are no further questions.

MR. WALKER: Mr. Chairman, in the morning are we going to pick up with these other two presentations?

MR. KEEL: The intent, Mr. Chairman, is to start with the Thiokol temperature discussion, but then try to constrain that to an hour and 30 minutes, and then go directly from there to the assembly demonstration prior to the tour. And then we will couple the wreckage reconstruction into the visit to the logistics facility, where we actually will look at the wreckage.

MR. SMITH: Excuse me. Are we going to have the discussion on the field joint assembly prior to the tour? It probably would be beneficial.

MR. KEEL: Yes, I just said that. That will be at 9:30. We are redoing the agenda right now.

(Whereupon, at 7:35 p.m., the meeting was adjourned.)

 


[Please note that some of the titles to the references listed below do not appear in the original text. Titles are included to identify and clarify the linked references - Chris Gamble, html editor]
[
573] [Ref. 2/13-57] NASA-JSC. FAILURE SCENARIO TEAM. [Ref. 2/13-58 1 of 2] NASA-JSC. ORGANIZATION CHART.

[574] [Ref. 2/13-58 2 of 2] NASA-JSC. Initial Actions and Operations.

[575] [Ref. 2/13-59] NASA-JSC. Failure Scenario.

[576] [Ref. 2/13-60] NASA-JSC. Failure Scenario: Failure Investigation of STS 51-L.

[577] [Ref. 2/13-61] NASA-JSC. Failure Scenario: SRB Leak.

[578] [Ref. 2/13-62] NASA-JSC. Failure Scenario: Failure Logic.

[579] [Ref. 2/13-63] [Leak area, square inches vs. Time, seconds]

[580] [Ref. 2/13-64] NASA-JSC. Failure Scenario: Summary Worksheet.

[581] [Ref. 2/13-65] NASA-JSC. Main Propulsion System.

[582] [Ref. 2/13-66] GH2 REPRESS LINE RESPONSE, Temperature vs. time graph.

[583] [Ref. 2/13-67] GH2 REPRESS LINE RESPONSE, Temperature vs. time graph.

[584] [Ref. 2/13-68] SRB yaw and pitch rate divergence.

[585] [Ref. 2/13-69 1 of 3] Marshall Space Flight Center- SRB ET AFT ATTACH STRUTS. [Ref. 2/13-69 2 of 3] SRB/ET AFT ATTACH STRUT LOWER & DIAGONAL.

[586] [Ref. 2/13-69 3 of 3] ET- SRB LOWER STRUT TEMPERATURES, Temperatures vs time graph.

[587] [Ref. 2/13-70 1 of 5] NASA-JSC. P9 RIGHT AFT SRB/ET STRUT LOAD, Indicator value vs. time graph.

[588] [Ref. 2/13-70 2 of 5] NASA-JSC. Failure Scenario: Summary Worksheet.

[589] [Ref. 2/13-70 3 of 5] ET-SRB LOWER STRUT MODEL. [Ref. 2/13-70 4 of 5] ET-SRB STRUT TEMPERATURES, temperature vs time graph.

[590] [Ref. 2/13-70 5 of 5] HIGH TEMPERATURE ALLOYS + EXAMPLE OF INCONEL.

[591] [Ref. 2/13-71 1 of 3] Relative Roll Rate, deg/sec vs. Time from L.O. graph. [Ref. 2/13-71 2 of 3] RSRB ROTATES ABOUT FWD AND AFT ATTACH POINTS WITH AFT LOWER LINK FAILED.

[592] [Ref. 2/13-71 3 of 3] RSRB IMPACTS ET INTERTANK. [Ref. 2/13-72] LAYOUT OF FWD ATTACHMENT ROTATION.

[593] [Ref. 2/13-73] INITIAL RESTRICTION FOR RSRB ROTATION. [Ref. 2/13-74] INITIAL RESTRICTION OF AFT RSRB ROTATION.

[594] [Ref. 2/13-75] INTERFERENCE AT FWD RSRB AND ET WITH 51.7° ROTATION. [Ref. 2/13-76 1 of 3] [Computer Aided Design showing SRB rotation]

[595] [Ref. 2/13-76 2 of 3] [Computer Aided Design showing SRB rotation] [Ref. 2/13-76 3 of 3] [Computer Aided Design showing SRB rotation]

[596] [Ref. 2/13-77 1 of 3] SMALL/MODERATE HYDROGEN LEAK.

[597] [Ref. 2/13-77 2 of 3] SMALL /MODERATE OXYGEN LEAK.

[598] [Ref. 2/13-77 3 of 3] STRUCTURAL FAILURE.



February 13, 1986 SESSION (part 1) | Volume 4 Index | February 14, 1986 SESSION