MSC-07631 19. Lunar module systems operations
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[edit] 19.1 PGNCS
- Cernan
PGNCS inertial subsystem performed exactly as advertised with the initial powerup and with the lunar surface powerup. did not get a restart light on the initial powerup. That was the only thing we did not get on the initial powerup. The ground said it was a GO.
I was a little disappointed in the AOT. It really performed like the simulator did. I could split the image on the reticle, both on the XY axis and the spiral cursor. By a slight movement of my eye, left or right or up or down, I could place the star within the reticle optical line of sight. I had to try and find a neutral position for my eye on the eyepiece so that I could be consistent in every one of my marks. That bothered me a little bit on the initial alignments until I got a constant position. That's something that, if I flew a lunar module again, I'd certainly like taken care of. The alignments came out good. But they came out good because I found an eye position where the star was focused and where the reticle was focused. I could put the star within the confines of the reticle for a good solid alignment by simply eye movement and not spacecraft or spiral cursor movement.
Rendezvous radar power up and checkout was outstanding in performance during the rendezvous. No anomalies. The landing radar was not only without anomalies, before we started our 70° yaw we started to pick up some indications of radar lockon. I was about halfway through the yaw to the 340 position during the landing when the radar locked on solid. Don't remember exactly what altitude that was, but it was far in excess of 35,000 feet.
- Schmitt
I think I did two or three PGNCS landing radar checks starting at about 2,000 feet. They were within the motion of the tape, exactly on with each other. No anomalies there.
- Cernan
Computer subsystem - I utilized the computer exactly like the simulator in terms of verbs and nouns during descent and ascent. Every one of them came up in what I called the prescribed amount of time. We never had any overload master alarms. We never had any program alarms. We never had any anomalous program alarms. It was a duplicate and repeatable of the way I handled the computer in the simulator. Exactly.
G&N controls and displays - The DSKY speaks for itself. The displays that came up on it were exactly what were called for both in the power up in the descent and the ascent. The other two primary displays are the needles and the crosspointers. During descent, the P64 needles again were nominal in terms of what the simulator told us they would be. The P66 needles in terms of fore and aft velocity were again exactly what I'd seen in the simulator in terms of fly-to needles to null the lateral velocities.
Crosspointers - I matched the crosspointers in terms of forward and lateral velocity with what I saw out the window in P66 for final landing. That is, lateral velocity on the crosspointer was effectively zero, and I agreed with that out the window. The forward velocity was probably 1 to 3 ft/sec on the crosspointer. The best estimation of my forward velocity out the window is that I had some. So, again, they were nominal.
Procedural data - The checklist, in terms of the flow through the power-up through the descent, and through the ascent, were well written. The PGNCS performed exactly as advertised in every respect.
- Schmitt
As we said about the CSM checklist, I don't think we had any changes to checklists that reflected any procedural errors prior to launch. I don't think we had any changes to the checklist that I can remember. The checklists worked perfect as far as I an concerned.
- Cernan
Let me back up and say something more about the PGNCS. The only time that the PGNCS surprised me was after TPI, when we had large residuals that I had not seen in the simulator. We had residuals in the area of 7 ft/sec in X and 4 plus or minus a few tenths in Y and Z at the end of the short nominal TPI burn. The simulator residuals were always much less than that. We had no problem. We just nulled them out with the RCS. But, nevertheless, they were there and it was about a 3-1/2 to 4-1/2 second burn. That surprised me just a little bit. We don't have the exact numbers written down because I rolled the residuals right away and went right into P35. I do know they were 7, 4 and 4 plus or minus a few tenths. Prior to descent, they gave us a zero gyro drift compensation. They said the PGNCS was right on. However, right after orbit insertion, it looked like we might have had some g sensitive drift in Y.
- Schmitt
You did. The AGS saw it.
- Cernan
For rendezvous navigation and the short rendezvous burn, we did not see any effect of it at all.
- Schmitt
The ground tweak was 7 ft/sec and the AGS would show 9 in the same direction.
[edit] 19.2 AGS
- Schmitt
Modes of operation - Nothing off nominal was used. Initialization went perfectly nominal. Calibration, the sighting with the exception of gyro cal, I think it was Z on the first activation, was slightly out of spec. Not out of limits but just slightly out of spec numbers that were given to me by Jerry Thomas, which was 0.3° spec limit. I think it was 0.5 or 0.6.
Rendezvous radar navigation on the AGS was done in AUTO with the exception of the post midcourse 2, where we put in three sets of marks manually in order to maintain the AGS state vector as close to docking as possible. The AGS state vector did just that - maintained itself within 2 ft/sec and was right with the PGNCS on range at the initiation of braking. Actually it was better than that at the initiation of breaking about 500 feet it was still within two feet per second.
Engine commands - All the engine discretes seemed to get into the AGS. The ground did not mention a single anomaly and I saw none on board. There were no electronic anomalies. Bum programs were perfectly nominal. In monitoring the DOI 2 and the midcourses, the AGS, as expected, did not see the short burst trim pulses that Gene made with the TTCA. The acceleration levels did not seem to be high enough to be sensed by the AGS external Delta-V.
Controls and displays were excellent. After every 400 plus 3 X, PGNCS aligned. There seemed to be about a quarter-degree constant bias between the AGS and the PGNCS alignment in pitch and yaw. I think it was a combination of pitch and yaw. A little bit of motion on the ball switching from PGNCS to AGS. One further thing on calibration - there seemed to be an accumulating accelerometer bias in X that was well below any significant problem. Probably something like 0.1 ft/sec. I noticed this after the first cal and then after insertion. After insertion I did do an accelerometer cal, 400 plus 7. That seemed to improve the problem although it did not eliminate it completely. It was not a serious problem with the AGS monitoring of its state vector.
- Cernan
AGS control check - I checked it out in both pulse initially. I checked all three axes out in pulse. I got the continuous rapid fire pulses. It checked out in three axes. I checked it out in rate command both for command and attitude hold. And it was a very tight system. I checked it out in min dead- band only. It was GO. There was absolutely nothing wrong with the AGS system either during powerup or during the phases of checkout.
[edit] 19.3 Propulsion System
- Cernan
The descent burn was extremely nominal in all respects. We monitored the start and attitude hold was steady. I monitored the throttle up on the PGNCS, watched the PGNCS command it, and watched the descent followthrough. It was 100 percent on the indicator, on time at 26 seconds. We saw a throttle-down again within a few seconds of that predicted from the ground, but exactly on time with that which we saw commanded from the computer.
The ROD, during the last phase of descent, during F66, responded extremely well. I knew exactly what rate of descent I had simply by the number of clips I put into the ROD.
Descent and ascent was a nominal operation as prescribed and as we saw in the simulator.
- Schmitt
The one thing we previously mentioned on caution and warning was that we got a descent quantity light after touchdown by several minutes, presumably due to either fuel sensing or or an actual fuel leak.
[edit] 19.4 Reaction Control System (RCS)
- Cernan
Attitude control modes - I flew it most of the time in pulse. After rendezvous for stationkeeping, nominal operation in all modes, nominal operation attitude hold in AUTO. Translation of control was nominal for ullage and for stationkeeping.
- Schmitt
The RCS ascent feed was good. We might add here that we did have a transducer shift in the ascent helium tanks. Tank 2, I believe, was reading hot. I believe that was what the ground called it as. They seemed to think they had a mixture ratio problem. They weren't completely sure. They had us terminate ascent feed early. It must have been 5 minutes or something like that. We terminated that early but there was no significant degradation in our RCS capability.
- Cernan
Every explosive device in the spacecraft audible.
- Schmitt
Except one. That was the second landing gear. Didn't you say you didn't hear that?
- Cernan
No, I heard it too. I could feel it when I hit the switch.
- Schmitt
I thought you said you didn't hear that.
- Cernan
The first landing gear operation, we felt, of course, the landing gear go out. The second one I could feel, in the switch, the activation.
[edit] 19.5 Electrical Power System (EPS)
- Schmitt
The batteries were excellent. There were no battery anomalies. The DC monitoring was no problem. I might mention that the ascent batteries did seem to require longer than nominal warmup time, although. I do not believe it was longer than expected with reference to the ground. We unfortunately got started 4 minutes late so we flew the first part of powered descent with battery 3 off the line in order to increase the load on the ascent batteries for preconditioning. That was not a problem at all. Battery 3 was put on somewhere in powered descent without any interference with that operation. DC monitor was fine. AC monitor was fine.
Power transfer CSM/LM/CSM went nominally in every case.
Abort stage configuration - Nothing to discuss that would be off nominal. Main buses performed nominally and dead facing was nominal.
Explosive devices in all cases seemed to perform as expected. We heard the pyros, I think, in every case except possibly the second set of pyros on the landing gear. That might be expected, not to hear those. We heard the first, but we may have been really hearing the bolts let go and the gear start to move into place.
Voltages were unchanged throughout the whole flight.
Lighting - There were no lighting anomalies.
Caution and warning - No anomalies. There were one or two configuration caution and warning signals which will come under ECS. What was that caution and warning we got right at the end of descent?
- Cernan
Descent?
- Schmitt
Right after touchdown.
- Cernan
No. All we got was descent quantity Y.
- Schmitt
That was after we vented, wasn't it?
- Cernan
No, it was before we vented. The descent quantity did not come on until after we landed and when we went through all the ascent checks. The fuel side was going down all the time. We never talked about it; we never asked.
- Schmitt
We don't know why that happened. That's right. The fuel side after touchdown continued to decrease. Sometime into the post touchdown pre-vent checklist, we got a descent quantity light. That was the only caution and warning anomaly.
[edit] 19.6 Environmental Control System (ECS)
- Schmitt
Oxygen cabin pressure was nominal except for a leaky main A reg, which potentially was caused by having my hoses stowed at one time with the suit in suit flow. That's up to the systems people to decide. But it did reset itself on time. It was not a serious leak. After that time, we did fly with only reg B in use. It was pretty clear that A was a usable reg; it just was leaky.
Cabin atmosphere was good, good ventilation, good odor clearing. The dust clearing was remarkably good, considering the amount of dust that we had. It was within a couple hours after ingress. Although there was a lot of irritation, at least to my sinuses and nostrils, soon after taking the helmet off, about 2 hours later, that had decreased considerably.
- Cernan
The LCG cooling was perfectly nominal.
The LCG cooling, I think, was a mandatory requirement pre-descent and pre-EVAs. I don't think the air cooling in the spacecraft was adequate prior to descent, which I said a long time ago, back several missions. This was really a godsend. We did not wear the liquid-cooled garments out of our own choice for ascent rendezvous, and I was very comfortable during that phase of the mission.
- Schmitt
Yes. I think had you worn them and not had cooling, you would have been uncomfortable.
- Cernan
Water supply. My first impression was that, after the first several gulps of water, there was a lot less gas in the LM water than in the command module water.
- Schmitt
True. We used all our water. We essentially ran dry at ascent. We drank a lot of water and we even used some additional water on our hands. Water glycol was nominal, and the suit circuit, with the exception of what I mentioned about REG A, was nominal.
[edit] 19.7 Telecommunications
- Schmitt
There was no problem monitoring the comm system. Operation of S-band high gain antenna was variable. We had some initial problems on the housekeeping day of lockup. It seemed to me to be a ground problem. I don't know their final resolution of that. It seemed that the same kind of thing happened to us on ascent, and again when we came around the horn prior to PDI. It seemed to be a ground lockup problem because it happened on the omnis as well as the high gain. We were just not getting a good strong uplink signal. I don't know what else to say. On ascent, as soon as we lit off, we lost the high gain, went over to omnis, and the omnis were giving the same indications - low signal strength, lots of noise, and a high squeal. Not a real high squeal, but an obvious squeal. It wasn't until somebody else did something that we got the comm back. I did not get the comm back; it just came back. We came through the command module for a little bit. Then they instructed me to do things I'd already done as far as going to the omnis and stuff, and then suddenly they came back up. So, I'm not sure what happened. But when we had S-band comm, it was excellent. Excellent voice.
- Cernan
The VHF comm after separation and throughout rendezvous was excellent.
- Schmitt
That's right. There was a little bit of a problem close in. I think, again, it was a question of overdriving too much.
- Cernan
The EVA antenna operations were all right, but the EVA comm was excellent throughout the first two and a half EVAs. The latter part of the third EVA, I began to get some noise in the background that the LMP did not get. It did not make the comm unreadable, but the noise was very evident. That lasted throughout the closeout of EVA-3. The LMP had no significant comm problems on the EVA, and had excellent comm. Procedures and operations of the audio center throughout the LM checkout and EVA changeover setup was nominal. It worked just as advertised.
- Schmitt
Flight recorders - I have no idea. I should mention that I probably left the LM DSEA on during the third EVA, because it was barber pole when we got back in. I suspect that we ran out of tape at that time. My regrets to Don Arabian.
Edits and errors by Eric Hartwell are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.5 license. The original NASA material is copyright-free.