Spacelog Apollo 13

That's correct.

We're deleting midcourse-3 and we've moved up the LM entry to 55 hours. So we'll merely follow all the—We'll follow all the procedures that leads up to LM entry that was originally scheduled for 58.

That's correct. You can start at 57 in the flight plan; call it 54 hours and press right on.

Okay. Then whenever we're finished with the LM, which we anticipate around 56:30, we'll commence PTC and sometime after that we'll do a P52.

That's affirmative. And did you copy the new high gain angles for 55 hours? The ones we had —

Okay. We're going to stop the PTC for LM entry at roll 285, and high gain angles are pitch 23 and yaw 267.

That's correct, Jim. And, 13, Houston. The computer is yours.

The computer is ours. We're in BLOCK, and exactly when do you want the TV to be cranked up?

You can crank it up sometime prior to 55 hours at your convenience just to set it up. We'll be expecting transmission at 55 hours.

Okay.

And, Houston, Apollo 13. One thing I missed about the O₂ fuel cell purge and waste and water dump.

Roger. We'd like the the O₂ fuel cell purge and waste water dump at 54:50.

Roger. We'll pick up those items at 54:50.

Apollo 13, Houston.

Go ahead, Joe.

All right, Jack. One thing we'd like to have done sometime soon is to have you cycle the cryo fans in O₂ tank 2 one more time. We'd like to see if we can get that sensor back.

Okay. O₂ tank 2 fan on now.

Roger.

Houston, 13.

Go, 13.

We—We have just one question, the LM tunnel vent valve. We're questioning why we're venting until the DELTA-V is greater than 1.7 if we are going to open up the tunnel, then pressurize the LM usually.

Right. Stand by on that.

13, Houston.

Go ahead.

Roger. The word on that, Jim, is that they want to insure the proper O₂ concentration in the LM when you get to the surface, and this is a method of doing that by bleeding out additional nitrogen.

Okay. Thank you.

And, 13, Houston. If Jack is up, I'd like to talk to him about the P52, briefly.

Okay. He's here.

Go ahead, Joe.

Okay, Jack. What they'd like you to do on this P52 at 49 hours, they've been observing a slight jitter in the optics shaft angle of about 0.2 of a degree plus or minus. Before you come out of the OPTICS ZERO position, at the start of this P52, they'd like you to just observe the shaft readout, and see if the jitter occurs on your direct readout there, and also they'd like you to briefly call up a VERB 16, NOUN 91 so we can look at the shaft and trunnion angles.

Okay. Let's see if I got it right. On the P52 at 49 hours, before coming out of ZERO on the OPTICS, observe the shaft and also call up 16, 91 and let you look at the shaft and trunnion angles to observe a possible jitter. See whether it occurs in the ZERO position as well as out of ZERO.

Roger, Jack. That's correct; and if you have time, now, I've got a flight plan update for you on looking for the Comet Bennett.

Okay. Stand by 1, Joe. And the commander's going off the air briefly.

Roger that.

Okay, Joe. I'm ready to copy the … now.

Okay, Jack. I'm going to read it to you, and then add some comments and we'll talk about it a little. This should occur sometime after 49:30. After the P52 realine at 49 hours, if time permits we would like the crew to investigate while in PTC if there is a roll angle in which the comet can be observed for photos. If there is, record the optimum roll angle for possible photography, prior to reinitiating PTC at 56:30 or so, whenever the guys are done in the LM, use P52 planet option, and the following half-unit vectors for tracking Comet Bennett at about 49:46. Are you ready to copy half-unit vectors? Over.

Okay. Go ahead, Joe.

Okay. R₁ plus 0.34202, R₂ minus 0.07374, R₃ plus 0.35719. Read back.

Okay. Copy R₁ plus 0.34202, R₂ minus 0.07374, R₃ plus 0.35719.

Okay. That's correct and the last sentence on the update is that you can expect AOS of the comet at a roll of 45 degrees and LOS at a roll of 155 degrees. Now, the deal here, Jack, according to the plots they showed me is, the comet appears to be about 10 degrees away from the Sun, and due to the geometry of the LM there shadowing the Sun, it would appear that you will be able to see the comet through the sextant without getting Sun shafting between roll angles of about 45 degrees and 75 degrees. It appears that as your roll gets higher than 75 degrees, although the comet is still in the field of view, the Sun is also in the field of view, and you probably will not have any success between 75 and 155 if you haven't got it from 45 to 75. If you do find that you can see the comet somewhere between 45 and 75 or 80 degrees, just note that roll angle and then if it's feasible we'd like you to photograph it after the LM entry part of the checklist. Over.

Okay, Joe. Let me give it back to you and see if I've got it here. After the P52, during our PTC you want us to use P52 and observe Bennett's Comet through the sextant; note a roll angle if we can find it visible. It would be visible somewhere between—ideally between 45 and 75 degrees, and we should lose it about 155 roll, and if we do see it, make an observation of whether it is photographable, note the roll angle for photographs to be taken after or prior to initiation of PTC at 56:30.

That's exactly right, Jack.

Apollo 13, Houston.

Go ahead, Joe.

We're ready to have to O₂ tank 2 fan off, and thank you.

Okay. Doesn't look like we got it back, huh?

Hey, Houston; 13.

13, Houston. Go ahead.

Okay, Joe. I got into P52 about 49:34. We loaded the planet—or Bennett Comet vectors into the planet option, and P52 tracked it all the way across except that it was always occulted by the LM, and we're in a roll angle of 155 now.

Roger. We're copying your roll angles. At what roll angle were you able to start tracking it, Jack?

Okay. At the time we entered it there, we were about 66 degrees roll, so either we started too late, or maybe somehow we got a wrong calculation on the roll angle.

Okay. Let me have GNC comment on that. I suspect that the roll angles we gave you were calculated for exactly 90 degrees pitch, and you're probably wobbling enough that they're not exactly correct.

Yes, I think you—You probably got the right idea.

13, Houston. Over.

Go ahead.

Okay, Jack. Notice you've secured from that, and that was going to be our recommendation, anyway. We're going to have the guys in the back room look at it and see if they can come up with some—with some better numbers based on the cone angle that—that you're traveling through, whether there are any roll angles that—that are available to you. And if there are, and we have time, we might give it another try; if not, we just will forget it.

Apollo 13, Houston. Over.

Go ahead, Joe.

Okay, Jack. I'd like to pass you a switch configuration on the CRYO O₂ TANKS and give you the reason. Right now, we'd like you to go to HEATERS tank 1, OFF; tank 2, AUTO, which is the opposite of the way you've got them now. Over.

Okay. Is this O₂ or H₂?

This is O₂, and stand by for a minute and we'll have a—Excuse me. This is H₂, Jack; it's H₂.

… is AUTO, … 2 OFF.

Okay, Joe. Do we have you back again?

Okay, Jack. We're getting you back, and I hope you copied my—my correction of my mistake. I'm talking about the H₂ CRYO TANKS. We'd like the tank 1 HEATER to OFF; tank 2 to AUTO. Over.

Okay. We lost you again. Here's our heater configuration now. H₂ HEATERS 1, OFF; 2, AUTO. Both O₂ HEATERS are in AUTO.

Okay. That's the configuration we want you in, and here's what we're thinking about. When we went to tank 1 AUTO, tank 2 OFF; we found that the heater cycle had a tank 1 pressure of about 233 psi, which is well above the caution and warning limit, and if we go to that configuration for sleep, we'll keep from getting CAUTION AND WARNING lights during the sleep cycle. Okay. In order to do that comfortably, we want to spend the rest of the day using more H₂ out of tank number 2, so as to get an unbalance in favor of tank 1, so at the end of the sleep cycle it'll all come out even. And that's why we have you in tank 1 OFF, tank 2 AUTO, now. We expect to get about a 3-percent unbalance over the next 10 hours; and prior to sleep, we'll call you to reverse the configuration again. Now the only disadvantage here is that, during the day, you will probably get a few CAUTION AND WARNINGS, and we just figured it would be better to get them now than while you were sacked out. Over.

I'll buy that 100 percent.