Apollo 11 CSI, CDH, Plane Change, TPI: So many questions, so little time.

Wedge313

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Thanks to a lot of help from you fine folk I am now station keeping with Columbia.

After struggling through CSI and CDH, TPI was very straightforward. It all worked out pretty much the way I think it was supposed to.

The Radar temp got as high as 198, but it continued to run without a glitch. During the darkside passage the temp dropped only to about 180, and started slowly climbing as soon as I passed back into daylight. But I assume I'll be shutting it off soon. It did it's job!

One question: Throughout the ascent there are many times we get a F 50 18 and are told to bypass by hitting ENTR. What's the reasoning? Wouldn't everything be easier if the LM was pointing straight at the CSM before thrusting? And the RR shaft and trunnion error needles on the FDAI....are those ever used? I may have missed that class.....

Anyway thanks for the help getting me this far.
 

Miriam

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Bypassing the automaneuvers saves RCS fuel and time. Otherwise you'd have to go to the maneuver att (RR breaks lock then, of course), execute the maneuver, go back to tracking att, reacquire...the RCS can translate in all 3 axes, so why not make things easier and use that?
 

Wedge313

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OK, next issue... getting ready to dock, and after configuring the LM per the checklist I've lost my ability to rotate the craft in PULSE.

Everything worked well after rendezvous, no problems translating or rotating. Checklist calls for V34E, then P00, still all works fine. MODE CONTROL to PULSE, no problems. But after entering V76, I lose the ability to rotate in PULSE, and I've lost my ATT HOLD (any translation produces un-commanded rotation).

I feel like I've missed a step. I tried to reconfigure the DAP (V48), but that didn't fix the issue. V76 is doing something I don't understand.

Thanks.
 

Miriam

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From my understanding of the LM DAP, V76 selects the minimum impulse mode, i.e. every time the stick is out of detent, the resp. thruster is fired once for the minimal time possible. It also deactivates att hold and auto maneuvers, so that's pretty normal. Maybe you are just confused by the somewhat odd behaviour of the LM when docked: rotational RCS is almost useless, as the cg and most of the mass is in the CSM.
 
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indy91

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PGNS minimum impulse mode also won't work with a bad framerate. The AGC emulator runs its computer cycles in its own loop (only together with PCM code for telemetry) so what usually happens if the framerate is below 40 fps or so is that the PGNS commands the RCS thruster on and then already off again in one timestep/frame. So the NASSP RCS code never recognizes that there ever was a RCS firing command.
 

Wedge313

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Maybe you are just confused by the somewhat odd behaviour of the LM when docked
I'm not docked yet, at this point I'm just station keeping. The Project Apollo Checklist has me in P00, all three attitude controls in PULSE, then V76E. And then instructs me to "Rotate to acquire face to face orientation...". Which is difficult because I've got zero rotation in any axis.

PGNS minimum impulse mode also won't work with a bad framerate
Probably my problem? On a good day my framerates are around 16 at 0.3x. At 1.0x I'll get 7 fps.

(Forward In Time) I'm docked. I don't know what's up with the LM RCS Rotation issue. I just decided to skip the V76 and left things as they were. Worked fine.

Also, after following the Project Apollo Checklist for the CSM, changing the DAP caused me problems with the CSM attitude, whenever I input a rotation command the ship began a strange oscillation, up/down left/right like it was trying to hold some attitude but it was a constant +/- 5 degrees in all three axis, I couldn't dampen the rates, and there was no way I could translate the ship to dock with it oscillating like that. So again I skipped the DAP change, left everything as was. Worked fine.

The actual docking maneuver/procedure was straightforward (as long as I retained the ability to orient the two vessels).

I have no idea what causes the LM issue (or the CSM issue) but if the goal was to dock, then I've checked the box and I'm ready to transfer some rocks from the LM to the CSM.

There's a lot here for me to learn, stuff I don't understand. But I think my computationally challenged laptop may be part of the problem.
 
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Miriam

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Docking is a completly passive thing from the LM side, even active att hold isn't allowed. You'd point the LM at CSM, hold that attitude for some minutes to damp the rates and then do V76, just before the CSM starts its translation.
The CSM DAP change is indeed odd. It sets the DAP to "CSM+LM ascent stage", which is -from my understanding- wrong before the vessels are actually docked. There's no sense in doing that, IMHO, as this shifts the DAPs idea of cg and inertia. Plus that there is no need for att hold or even an immediate maneuver right after docking. To the contrary, once capture was achieved, both vessels were left to drift freely for some time to allow the wiggling to damp down. Active attitude control was reestablished once both vehicles were hard docked, and then it would've been the right time to change the DAP mode. I've always ignored that instruction and obviously avoided some problems this way.🤷‍♀️
 

rcflyinghokie13

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Docking is a completly passive thing from the LM side, even active att hold isn't allowed. You'd point the LM at CSM, hold that attitude for some minutes to damp the rates and then do V76, just before the CSM starts its translation.
The CSM DAP change is indeed odd. It sets the DAP to "CSM+LM ascent stage", which is -from my understanding- wrong before the vessels are actually docked. There's no sense in doing that, IMHO, as this shifts the DAPs idea of cg and inertia. Plus that there is no need for att hold or even an immediate maneuver right after docking. To the contrary, once capture was achieved, both vessels were left to drift freely for some time to allow the wiggling to damp down. Active attitude control was reestablished once both vehicles were hard docked, and then it would've been the right time to change the DAP mode. I've always ignored that instruction and obviously avoided some problems this way.🤷‍♀️
I just did a little digging on this and you are correct, that is actually out of place. Looking at one of the original Apollo 11 flight plan scans it was typed incorrectly as there is a little hand drawn arrow placing that after capture. The flight plan was incorrect and therefore the reformatted version was and the Checklist MFD as well.

I will push this change shortly.
 

Miriam

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Argh, now you've been too fast. I just flew a rendezvous again and stumbled over the "Reset ET" lines. I'd suggest to write 'Update ET' instead, as 'reset' is -for me- hitting the reset sw and stop the timer. But you want it to show the correct time to the next maneuver, so 'update' is better.
 

rcflyinghokie13

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Argh, now you've been too fast. I just flew a rendezvous again and stumbled over the "Reset ET" lines. I'd suggest to write 'Update ET' instead, as 'reset' is -for me- hitting the reset sw and stop the timer. But you want it to show the correct time to the next maneuver, so 'update' is better.
This one I will disagree with as the verbiage in the procedures is actually "Reset" not "Update" which means literally resetting the ET and then putting in the new time as necessary...

EDIT: For clarity: http://www.ibiblio.org/apollo/Documents/Mission_G_Rendezvous.pdf
 

Wedge313

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Appreciate the above posts. This is my first time trying this, and the DAP changes for both LM and CSM seemed a hair out of sequence to me. I ended up doing what (I think) Miriam described, oriented the LM first then V76E, and then waited until I was docked to change the CSM DAP to the CSM + Ascent Stage DAP.

I love NASSP. This is the steepest learning curve I've undergone in years! (And I'm having a blast). Thanks for the help.
 

rcflyinghokie13

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Appreciate the above posts. This is my first time trying this, and the DAP changes for both LM and CSM seemed a hair out of sequence to me. I ended up doing what (I think) Miriam described, oriented the LM first then V76E, and then waited until I was docked to change the CSM DAP to the CSM + Ascent Stage DAP.

I love NASSP. This is the steepest learning curve I've undergone in years! (And I'm having a blast). Thanks for the help.
Yep as I stated it was actually incorrect in the actual flight plan. Found the edit and made the changes by moving the DAP change for the CSM to CSM+LM ASCENT to after capture. Its fantastic to see you all notice these things as in this case showed the actual procedures to be incorrect :)
 
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Wedge313

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I'm just amazed at how accurate the whole NASSP simulation seems to be. Having the checklist on the MFD is an incredible tool. And then I have the option of doing the steps manually, or using the AUTO feature and it does everything for me! Even I can't goof it up in AUTO!

My last experience programming was with FORTRAN, feeding punch cards into a IBM 360. So what you all have done with NASSP seems like sorcery to me.
 

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Wedge313

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Ha! I can't remember what I had for dinner yesterday, let alone remember any of my rudimentary FORTRAN knowledge from 50+ years ago (I do remember something called a "DO Loop", and that I got caught in them a lot? Other students' programs had to wait in the que until I fixed it. Didn't help make many friends.)

Also I remember we would use the used punch cards to make Xmas wreaths. But I digress.....

Your FORTRAN project is way beyond me. But I think it's great you're preserving the knowledge; at one time it was the cutting edge.
 

Wedge313

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Very minor Project Apollo Checklist question: I don't know if this is a glitch in the checklist or a case of I don't know where to look:

In the LM Shutdown procedure, there are two items: the first says "Sys A & B Main SOV -tb(4)- gray" and the next "Sys B Main SOV-tb(2)-gray". Should these two steps be combined into one that reads "Sys A & B Main SOV-tb(2)-gray"?
 

rcflyinghokie13

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Very minor Project Apollo Checklist question: I don't know if this is a glitch in the checklist or a case of I don't know where to look:

In the LM Shutdown procedure, there are two items: the first says "Sys A & B Main SOV -tb(4)- gray" and the next "Sys B Main SOV-tb(2)-gray". Should these two steps be combined into one that reads "Sys A & B Main SOV-tb(2)-gray"?
Yep looks like a copy paste error! I have fixed it.
 
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