Apollo 9: P52 Opt 1 (Preferred) at T+5:10:00 Question

rcflyinghokie

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First off, I appreciate you taking the time to help me work through this...


See screenshots. It's near the SCT crosshairs, but not close enough to been seen in the SXT.


Another learning opportunity for me.... before the PAD and P30 target load, the DAP is set at 21111, 11111 and the gimbal angles are -00135 and +00133.

The PAD gimbal angles are +00105 and -00023.

I tried this a couple of ways. First I left the V48 gimbal angles as they were, then ran through the P30, started P40 then exited with P00, ran P52 opt 1, V49 to the burn attitude (PAD 000/356/001) then V41N91. The SXTS looked like the photos.

The second time, I did the uplink, then changed the V48 to 21102, 01111 and changed the gimbals to the PAD angles +00105 and -00023. Then I ran P30, started P40 exiting with P00, P52 opt 1, then V49 to the burn attitude. The SXTS star looked slightly closer to the center of the SCT but still not visible in the SXT.

I'm doing these about 50 minutes before the burn, but even if I wait until 30 minutes before the burn the star is not visible in the SXT.


"manually maneuver" to what? Do I need to have a star centered in the SCT crosshairs? Or just visible in the SCT? After I choose a star and manually enter it, what maneuvering do I do before I choose and manually enter the second star? When I start over with the V32, do I maneuver again to a totally different set of stars? We go through this three times, and this confusion on my part is why I'm eating up so much time.

And will this alignment check correct what looks like an incorrect alignment?

Apologies for dragging this out, but I'd like to try and understand what I'm doing wrong.
Don't worry about dragging this out we will get to the bottom of it!

The alignment check you are to manually maneuver the spacecraft to have a star in the telescope, then you select that star in the DSKY and let the optics drive to that star, and you repeat this a few times without torqueing the IMU.

I have pasted the procedure and the P52 steps from Apollo 9 maybe it will help clarify things?

For your sextant star check, its possible you have a bad alignment or your P30 REFSMMAT doesn't quite line up with the pad one. I will run the last save you shared and see what it looks like (assuming that's the alignment you had where it didn't line up.)
 

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rcflyinghokie

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I just checked the alignment in that one scn you posted, its a few degrees off which would explain the star not being in the sextant. Take a look at FDAI 1 (I did a fresh P30 REFSMMAT) and FDAI 2 (your alignment prior)


1664988220111.png
 

Wedge313

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I just checked the alignment in that one scn you posted, its a few degrees off which would explain the star not being in the sextant
So If I run through the Alignment Check correctly, it should tweak the P52 opt 1 alignment enough that the SXTS check should look OK?
 

rcflyinghokie

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So If I run through the Alignment Check correctly, it should tweak the P52 opt 1 alignment enough that the SXTS check should look OK?
No the alignment check doesn't change your alignment, since you aren't torqueing anything. You are just making sure the optics properly drive to a star you have selected.
 

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OK, so we never torque anything with the alignment check, were just eyeballing where the optics are driven when we manually select three different star pairs?

That being the case, I'm still not clear on why I can't get the alignment correct. If my alignment doesn't look right after the first P52, if I run P30 again and start P40, will it generate a new REFSMMAT so I can run another P52? What magic did you perform to get a good alignment from my bad alignment?

Thanks
 

rcflyinghokie

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OK, so we never torque anything with the alignment check, were just eyeballing where the optics are driven when we manually select three different star pairs?
Correct, its a check of the optics driving. It is run 3 times but every time the torqueing is skipped, so your alignment never is changed during.

That being the case, I'm still not clear on why I can't get the alignment correct. If my alignment doesn't look right after the first P52, if I run P30 again and start P40, will it generate a new REFSMMAT so I can run another P52? What magic did you perform to get a good alignment from my bad alignment?
All I did was verify the DAP information, loaded P30 and cross checked it with the pad, and at the F37 at the end did a 40 E then V37E 00E.

I then entered P52 option 1 and did a normal PICAPAR alignment and torqued at the end.
 

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Tried three P30/P40/P52/V41N91 run-throughs, I'm not getting the star check to work. Which tells me my alignment is wrong.

Which means I don't know what the bleep I'm doing.

Here's a save from 4+52. At this point the PAD is available, but I have not uplinked the target load.

From this point what I have been doing is:
1. Uplink the target load.
2. Change the V48 to incorporate the PAD gimbal angles.
3. Run P30. At the end of P30 with a flashing V37 I enter 40E (begin P40)
4. P40 begins, F50 18 displayed. I enter V37N00E (P00)
5. Perform P52 opt 1
6. Run the alignment check. The optics seem to line up correctly.
7. V49 to the burn attitude
8. Run V41N91E. I still get the inaccurate star check.

After that I ran P30 again, into P40, exit with P00, another P52 opt 1, skipped the alignment check, V49 to burn attitude, V41N91E, star check still not good.

No idea where I'm going off the rails. From this save, can you run through it all and get a good star check?

One note, my GDC is mis-aligned here, I had FDAI 2 in ORB RATE maneuvering while visually tracking the SIVB and may have messed it up? I planned to do a GDC align after the P52.
 

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rcflyinghokie

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I went through all the steps and at TIG -30 I have Sirius in my sextant. Are you in P40 when you do the check? What attitude are you in? Remember the burn attitude on the pad is before the REFSMMAT change.
 
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Wedge313

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You may be on to something here....

Are you in P40 when you do the check?
No. I did a V49 to the PAD burn attitude, then hit ENTER and then V41N91E and input the PAD shaft/trunion.

What attitude are you in?

PAD RPY of 000/356/001

Remember the burn attitude on the pad is before the REFSMMAT change.

So if I start P40, I'll see a different attitude than the PAD attitude? (I'm guessing 000/000/000?)

So if I understand this, after the P52 and alignment check I should V49 to the PAD attitude, then V41N91E and input the PAD values. At this point the star may not be in the SXT. THEN I start P40 where I'll get the F 50 18, maneuver, and THAT'S when the star should be in the SXT?
 

rcflyinghokie

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No. I did a V49 to the PAD burn attitude, then hit ENTER and then V41N91E and input the PAD shaft/trunion.
So that burn attitude is based on the launchpad REFSMMAT, so that's what you maneuver to before the alignment and puts you at the burn attitude after alignment or close to it.
PAD RPY of 000/356/001
Yep that's pre alignment attitude not burn attitude.
So if I start P40, I'll see a different attitude than the PAD attitude? (I'm guessing 000/000/000?)
Yes correct, P40 should have the burn attitude with a P30 REFSMMAT (0,0,0). Though the actual mission omitted a dap gimbal change before the alignment so the burn attitude ended up being slightly off of zero. I have incorporated this "mistake" in the checklist MFD procedure as well.
So if I understand this, after the P52 and alignment check I should V49 to the PAD attitude, then V41N91E and input the PAD values. At this point the star may not be in the SXT. THEN I start P40 where I'll get the F 50 18, maneuver, and THAT'S when the star should be in the SXT?
Before the P52, you should maneuver to that attitude, then do your P30/P40 and P52/alignment check. Then you start P40 and maneuver to the computed burn attitude (should be almost no movement since your pre alignment pad attitude should have been burn attitude with a P30 REFSMMAT) and then do the star check. The checklist MFD procedures reflect this order and the omission of the dap as well.
 

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Also I made some tweaks to the SPS-1 checklist for Apollo 9 yesterday based on this confusion, maybe it will help the order of operations a bit better :)
 

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OK, I think I've got it. After starting P40 I looked at the SXT and the star was in view- just barely, but it was in view. The burn itself seemed ok.

FWIW, I just completed SPS-2. Basically the same procedures, but interestingly this time when I did the V49 to the PAD attitude and then the V41N91 (without starting P40) the SXTS star was almost centered in the SXT. The PAD attitude was 000,000,000, so it was basically the P40 attitude. That burn seemed to go well also. I think I finally grasp the "preferred IMU orientation is calculated on board" idea.

One unassociated question: I've got Fuel Cell #2 powering both Main A and Main B. On other flights I'm pretty sure we had FC #2 only on Main A. Is this unique to Apollo 9, or did I miss a step?

Thanks again for all the help.
 

rcflyinghokie

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FWIW, I just completed SPS-2. Basically the same procedures, but interestingly this time when I did the V49 to the PAD attitude and then the V41N91 (without starting P40) the SXTS star was almost centered in the SXT. The PAD attitude was 000,000,000, so it was basically the P40 attitude. That burn seemed to go well also. I think I finally grasp the "preferred IMU orientation is calculated on board" idea.
Yeah later pads are burn attitudes based on the REFSMMAT intended for the burn. That's why you have the remark in the SPS-1 pad saying its using the launchpad REFSMMAT.

Also, you will notice on later mission flight plans you have a maneuver attitude before a burn or P52, that is usually an attitude using an old REFSMMAT so the spacecraft is in an expected alignment post alignment if this makes sense. Attached 15's FP excerpt as a demo.
One unassociated question: I've got Fuel Cell #2 powering both Main A and Main B. On other flights I'm pretty sure we had FC #2 only on Main A. Is this unique to Apollo 9, or did I miss a step?
You might have loaded missions before we realized we were mistaken with the fuel cell bus tying. Older checklist mfd files in older variants of NASSP has this incorrect but I think I corrected for all missions, though the "default" checklists used in RTCC missions (12-17) might still be the old version I will check.

TLDR; Prelaunch for all missions should have FC1/2 on MN A and 2/3 on MN B. (See attached launch checklist from Apollo 9)
 

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TLDR; Prelaunch for all missions should have FC1/2 on MN A and 2/3 on MN B.
So, this config with FC #2 on both MN A&B is the correct config? I went back and looked at a couple of other flights I've done (Apollo 12 only a few weeks ago) and I had FC #2 on MN A only. That was incorrect?
 

rcflyinghokie

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So, this config with FC #2 on both MN A&B is the correct config? I went back and looked at a couple of other flights I've done (Apollo 12 only a few weeks ago) and I had FC #2 on MN A only. That was incorrect?
Apollo 12 launch checklist for instance:
1665065470703.png

Later missions used a different configuration
 

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Yeah, I missed that on Apollo12, I think I may have used the PAMFD Checklist in AUTO to expedite the pre-launch stuff, but I didn't notice the difference from the checklist. I was used to looking at the MN A gray/gray/bp, MN B bp/bp/gray config from Apollo 15,16, and 17.

When I saw it here, I thought I missed some post-launch config change, but I guess that's how it's supposed to be configured.

Thanks.
 

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OK, SPS-3: at 45 sec before shut-down we move the THC CW, using MTVC.

Was I supposed to leave the pitch and yaw trim at zero? The first time through when I turned the THC CW, the engine snaps back to zero/zero and the spacecraft yaws/pitches, I wasn't quite ready for that...

I re-did it a second time, this time I set the trim wheels to the burn gimbal angles. When I switched to MTVC it was a much kinder, gentler event.

On other flights the MTVC check was a little different, and we would set the trim with the trim wheels. Is it different on Apollo 9, or did I just miss it?
 

rcflyinghokie

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Was I supposed to leave the pitch and yaw trim at zero? The first time through when I turned the THC CW, the engine snaps back to zero/zero and the spacecraft yaws/pitches, I wasn't quite ready for that...

I re-did it a second time, this time I set the trim wheels to the burn gimbal angles. When I switched to MTVC it was a much kinder, gentler event.
Yeah you are supposed to set the GPI trim wheels before any SPS burn, the zeros are why you got this transient.

They were not supposed to be left at zero for the burn, especially for an MTVC test.
On other flights the MTVC check was a little different, and we would set the trim with the trim wheels. Is it different on Apollo 9, or did I just miss it?
Actually they are set on every mission/SPS burn. About a month ago we found that omission in the checklist MFD files and fixed it to tell the user to set them to the pad trim values.
 

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About a month ago we found that omission in the checklist MFD files and fixed it to tell the user to set them to the pad trim values.
Ok, I must be a little out of date, I'm on v1951. But leaving the trim at zero for the MTV burn was a great teaching moment, really hammers home the reason for setting the trim.

Finished the SPS-4 burn, starting the rest period, I'd like to bother you with a few more questions...

The PAMFD Checklist has a step in yellow: "Copy SPS-xx Gimbal Angles", but I never get a PAD or any gimbal angle info until later when the P30 PAD shows up. Not a big deal, but I guess this was a part of the P30/P40 IMU orientation process, to get the angles into the DAP before starting P40?

When the PAMFD Checklist has us run P30, there's the "Set DET" step. But we're always running P30 well over an hour out. I've been re-running P30 once I'm within an hour of the burn just to set the DET, but is there a better way to do this?

When doing the waste water dump, we move the PRESS RELF selector to DUMP A. Was there ever a time when the procedure would also close the POTABLE TANK INLET? For some reason I've got that stuck in my mind.

Finally, after the SXT star check, the checklist has us OPT ZERO-ZERO, OPT ZERO-OFF (15 SEC), OPT MODE-MAN. I'm still displaying the V41, if I follow these steps I'll zero the optics but when I go OPT ZERO-OFF the optics will go back to the V41N91 setting. Shouldn't I V37N00E first, or go to MAN before zeroing?

Enough for now. Thanks for the help.
 

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rcflyinghokie

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The PAMFD Checklist has a step in yellow: "Copy SPS-xx Gimbal Angles", but I never get a PAD or any gimbal angle info until later when the P30 PAD shows up. Not a big deal, but I guess this was a part of the P30/P40 IMU orientation process, to get the angles into the DAP before starting P40?
Right so remember that case where SPS-1 gives you a maneuver attitude before you realign? Apollo 9 was given these as well before SPS burns. Our MCC doesnt give you these yet but its on the list to add. In the mean time, these are placeholders as they are found in the actual flight plan.

When the PAMFD Checklist has us run P30, there's the "Set DET" step. But we're always running P30 well over an hour out. I've been re-running P30 once I'm within an hour of the burn just to set the DET, but is there a better way to do this?
I have always wondered about this as well, almost every flight plan has you "Set DET" over an hour out. I think its just a general step put in with P30's regardless when it is started up. There might be a "better way" but then we deviate from the flight plan timelines. If your P30 is around an hour from the burn you could wait a little before updating it but that is up to you.

When doing the waste water dump, we move the PRESS RELF selector to DUMP A. Was there ever a time when the procedure would also close the POTABLE TANK INLET? For some reason I've got that stuck in my mind.
Its funny this procedure changed slightly mission to mission. Some had the inlet closed like 11, but later missions like 15 did not have it in the AOH procedures.

The potable tank inlet would be closed if there was a suspected problem with the discharge water from the fuel cells (ie pH hi warning) or some other contamination issue. It also could be used to prevent the tank from overfilling. I can give you more detail on how all the water systems connect if you wish.

Finally, after the SXT star check, the checklist has us OPT ZERO-ZERO, OPT ZERO-OFF (15 SEC), OPT MODE-MAN. I'm still displaying the V41, if I follow these steps I'll zero the optics but when I go OPT ZERO-OFF the optics will go back to the V41N91 setting. Shouldn't I V37N00E first, or go to MAN before zeroing?
This is an interesting thing you pointed out. Some later missions actually kept the switch in ZERO during SPS burns to prevent any issues with TVC servos.

I will do some research and see if I can verify/fix this mission to mission to be more accurate. But the extra driving you get shouldnt cause any issues. Feel free to leave the switch in zero for now if you wish.
 
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