Spacelog Apollo 13

Okay. Turning to the next page and the last page, Jim, 34. Top of the page, “Monitor DELTA-V_X via 470.” Scratch next two lines, “When propellant quantity equals 37” and the “DESCENT HELIUM REG.” Scratch “TTCA commander, reduce to 10 percent.” Now we want you to add a line; “shut”—It's a shutdown criteria, “shutdown on burn time minus 1 second.” Over.

Okay, “The shutdown is on burn time minus 1 second.” Let me give you an example. If we have a 30-second burn, we're going to shut down at 29 seconds. Is that correct?

That's affirmative. We'll give you the pad, be coming up here from FIDO in a couple of hours, I guess, when we stabilize out on our tracking. The reason for—If you're ready to copy out a couple of more steps, and then I'll explain the reason we want to shut down on this burn time minus 1 second. Picking up on "When DELTA-V_X —

Roger.

Start with step 3 again. “When attitude—When at attitude, ACA out of detent.”

That's Roger. Next step, step 4: “ATTITUDE CONTROL to YAW”—Correction, “ATTITUDE CONTROL: YAW, to MODE CONTROL.” Over.

Okay. Step 4 is “ATTITUDE CONTROL: YAW, to MODE CONTROL.”

Roger. Step 5: “When rates are less than 0.05 degrees per second, ATTITUDE CONTROL: YAW, to PULSE.”

Okay. “When rates are less than 0.05 degrees per second, ATTITUDE CONTROL: YAW, to PULSE.”

Roger. Step 6: “Spin up to 0.3 degree per second in yaw,” and that takes about 21 pulses. Step 7—Yes.

Okay. Go ahead.

Okay. Step 7: “MODE CONTROL, AGS, OFF.”

Okay. Step 6 was “Spin up to 0.3 degrees per second in yaw”; that's about 21 pulses. Step 7 was “MODE CONTROL, AGS, to OFF.”

That's affirm. Step 8: “Power down per power”—Correction, “Power down per contingency checklist page Power 5.” Over.

Okay. And step 8 is Power down per contingency checklist Power 5," and I take it that's been revamped considering our situation. Okay.

That's affirmative, Jim. That's the one we gave you last night after the big burn, and we'll use that one as modified by—by us. This—we tried this PTC under AGS in the simulator and, of course, no slosh or anything, but it seemed to work pretty good by nulling the rates using the TTCA in pitch and roll and letting the ACS do it in yaw. You null the rates by looking at the error needles and just watching those, and when they don't—when they stop moving, then you got it within the limits of what we want. Over.

Okay. And I guess, Charlie, you have no—Do you have a ATT hold mode in pitch and roll at all in this configuration we're in, or do we have to use the TTCA?

We feel like we have to use the TTCA. The AGS gains are not too good in pitch and roll in this configuration. It'll hold it in yaw but it won't in pitch and roll. Over.

Okay.

And you'll have—During the burn, of course, you'll be controlling pitch and roll via the error needles with the TTCA also, and it's the little scheme that we've practiced in some of the SIMs. Over.

Right. Understand.

And, Houston, want to make sure that we allow enough time to get to the proper attitude for the burn so that we can be sure we establish the proper attitude and don't have to rush the burn.

Roger, Jim. We -we're looking right now, tentatively, at starting this about 45 minutes before the burn and our sensitivity is—not too bad on this burn. We can go 30 minutes either way and not affect our DELTA-V. Over.

Okay. Fine. And do you have a handle on just how long the burn will be? In time?

It's looking like at about 7.8 seconds and about 15—Correction, 7.8 feet per second and about 15 seconds. Over.

In about 18 seconds?

Negative. 15. 1 5.

1 5. Okay.

And one other point is that we'd like to remind you that this is going to be in blowdown and both REGs B closed but we've got plenty at the 10 percent.

Understand.

And, Jim, in the simulator with our configuration that we had here, the thing is real stable at 10 percent, so we don't think you'll have to tweak very much at all using the TTCAs. Over.

Okay. Understand.

And I'll give you back to Vance. Thank you.

And thank you.

Aquarius, Houston.