Spacelog Apollo 13

Hey, 13; Houston. Go ahead.

Okay, Joe. I've started into P52 here. I've proceeded on option 3, and on the dis—1520—1525 display, I've called up 1691. I'm going to let you observe and see while the—the shaft angle while the OPTICS are still in ZERO.

Okay. Roger that, Jack. We're looking at it, and I'll give you a mark as soon as GNC is happy.

Okay. Real fine.

13, Houston. Jack, could you give us a readout on your counter now?

Okay. I'm showing a shaft of 0.2 and a trunnion of 359.92.

Roger. Copy that. Is there any jumping around on the shaft?

Go ahead, Houston.

Roger. For Jack, we missed the star angle difference on the P52. Would you read us that?

Roger, Houston. It was all balls.

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.