Spacelog Apollo 13

But, Joe, assuming the S-IVB is still stable. The object I was looking at was definitely tumbling.

Okay, Fred. As I recall, it was stable then, although it's tumbling now.

Okay. It probably was the SLA panel I picked up.

Right. Incidentally, I guess the guys in building 6 —

Oh and I think we -

Go ahead, Jim.

I—I think we answer to number 9. We—at around 5:32, I think, was when we think the number 5 light came on in the S-II, and a definite vibration which was more than just a high-frequency vibration we got with the normal S-IV burn, and then the light came on. I called ECO thinking from the training that it was 7:42 and looked up at the time and realized it was early. And then, soon after the light came on, the vibration stopped and the engine or the booster smoothed down. It was very smooth from there on.

Okay. This may be a stupid question, but do you have any idea what the frequency of it was?

Only to say that it was much higher—I couldn't really guess now. It was rather a rapid longitudinal vibration.

Okay, Jim. Stand by now for a minute, we're going to switch OMNI.

Houston, 13, …

13, Houston. I read you. We still have quite a bit of noise on the loop.

I'll stand by. Roger.

Okay, Jim. It should be pretty good now. We copied you answering question number 9.

Do you want any more comments on the S-IVB vibrations?

I don't think so. When you get all done, I'll—I'll make a quick check to see if the booster people have any—any additional questions. You skipped number 8, Jim; could you go back to that for a second?

Okay, stand by.

Our only comment there, Joe, was that the burn on TLI, to our knowledge, was about 3-3/4 second longer than had been predicted and that was the only thing that we really noticed; otherwise, looked like PI [?] was nominal at cut-off.

Okay, understand.

Jim, while we're waiting to see if they have any more questions, I'd like to read you the booster people's preliminary analysis on the—the S-II cut-off. Over.

That would be very interesting. Go ahead.

Okay, preliminary analysis of the data indicates that the center S-II engine vibrated at a somewhat higher amplitude than we've seen on previous flights, and it started at about 160 seconds into the S-II burn. As a result of these vibrations, the engine chamber pressure decreased to the level where the two low-level thrust sensors, the thrust-okay sensors, initiated center engine cut-off. Early evaluation of data indicates that no damage occurred to the engine, and the cause of the increased vibration amplitude is still under investigation. Over.

I thought it was the center engine.

Yes, right.

Joe, do you have any word on what marks we had for TLI?

At the time of TLI, as I recall, you had 6 seconds longer than the nominal burn which was 3 seconds longer than the B-sigma low burn, and you were also GO for a second-opportunity TLI if we had required one.

Okay, we were just wondering because it appeared to us that we had a longer TLI burn than had been predicted.

Yes, you did. We confirmed that—that—that cut-off time just about as you saw it, and I don't have an explanation for it, but it was within the B-sigma margin.

13, Houston.

Go ahead.

Roger, we have no further questions. All the answers were clear and satisfactory, and we thank you very much. You can press on with the rest of your busy day.

And, Houston; 13.

13, Houston. Go ahead.

Okay, Joe. Out window 5, I just picked up the tumbling object again so, for sure, it must have been a SLA panel. I don't think we could still be in the proximity of the S-IV at this time.

I don't think so, Fred. It's several hundred miles aft of you. 700 miles is—is the number, I'm told. And since the SLA panel didn't make the midcourse correction, that might be it.

Yes, it's, I can't really tell for sure even through the monocular that it is, but it looks the same relative position to the stars. And the best I can tell about the same intensity and still about the same distance from us.

Can you see it tumbling. Does it have a shape, or is it a point?

No. I can tell it's tumbling; I guess the flat side not only is facing me, it's not only much brighter, it also grows larger.

Okay. Very interesting. We'll see if we can figure out where that's relative to you. They keep updating the S-IV impact on us a little bit. The last guess we had was that it will impact about the same longitude we gave you but close to zero latitude and a little bit later. You still won't be able to see it. And they're saying it might make a —

Roger.

— they're saying it might make a 100 to 120 foot crater, too.

It'll still be past the terminator for us for awhile.

Right. It will be at about the REV 20 terminator, so it will be late in your lunar orbit activities before you will be able to photograph it, and FAO is looking at whether we can work that in or not.

Houston, 13.