Apollo 9 - LM activation before GET 048:00:00 issues?

thermocalc

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Hi to all, I am back with some new issues/questions.
I am still alternating between A7 and A9 (having completed A8), I arrived at the moment where you need to activate the LM before getting the PAD for the docked DPS burn.
here are the problems:
1) when I do the IMU coarse alignment I will enter into the AGC the LM O/I/M angles read on the LGC page of the PAMFD setting LVLH by pressing REF; in my case I have about these values:
LM O/I/M = 310.79 102.84 2.17
so I enter them as: V41 N20, +31079E +10284E +00217E
BUT: I see that only the FDAI on the panel 1 is moving, the FDAI on the panel 2 is not moving, still keep showing 0-0-0 degrees.....am I missing some cbs to power up the FDAI2 ???
if I then do V16 N20 I got more or less the same angles......BUT..
2)The FDAI reading is "weird" .... if i have to read the R_P_Y as for the FDAI for the CSM (with ROLL and YAW interchanged due to different MG set-up between the LM and CSM IMU axis) I can see/read the information displayed by V16 N20 not like (R-P-Y angles, as in the CSM) but as for (Y-P-R) .... still the attitude information that I "read" from the FDAI1 is a little bit different from what is displayed on the AGC; namely the "roll pointer" is about 2 degree ---- which seems to confirm me that in the AGC R3 is showing indeed Roll information) ---- the pitch is ok as it should be at about 103 degrees ---- but the yaw is about 50 degrees, looks like it displays 360-310=50 degrees .... not the 310 degrees as indicated by the register R1 .....

I tried to open the default scenery in the A9 historical missions (the one at T-6min to DPS docked burn) I saw both FDAIs are run and aligned but if I move the vessel to another attitude and I enter V16 N20 to read the angles on the AGC again I can see that the angles shown on the FDAI1 are not equals to the values reported in R1-R2-R3 in the AGC ....

last issue: in two saved scenarios, one before the RCS cold firing test and one before that, when I arrive to GET 048:00:00 (while steel busy to finish checklists items in the LM) i got the MCC message for SV update, I immediately go back to CSM (interrupting what I was doing) and set everything for get the uplink, but after pressing 2 on the MCC menu i don't get any uplink .....and more important I never get the burn PADs....

what is goin on? am I evidently missing some checklist item at the correct time? or can they be again some sort or "orbiter glitches"? or issues related to frame rates -> my PC.

out of the record I would like also to point out some other issues, I had with A9, but never on A8 and so far never on A7 (but A8 and A7 were/are with 2010P1 orbiter...)....sometimes while making time acceleration to x10 or x30 (more I can't go with my PC) all a suddenly I got NO ATT, RESTART, PROG lts ON on the AGC in the CSM ..... normally when it happens I just exit and re-start a saved scenario few hours earlier and the same issue doesn't happen again .... but still .... what could cause it? time acceleration seems to be the root cause surely....

last: now I am saving always using the scenario editor and pressing SAVE when I want without exiting the sim (as explained to me in this forum).

Thank you to take time to read me.
cheers, Paolo.

PS: compared the CSM the LM seems to be very complicate to handle ... hope to can manage it one day :-(
 

thermocalc

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HI, sorry, I did some more testing...
in the first picture you see what I am getting while coarse aligning the IMU of the AGC using the angles provided by PAMFD (see angled in the right bottom corner) .... see also the OG/IG/MG in the registers R1,2,3 of the AGC and the FDAI1 ball --- you see that the FDAI ball show as YAW of about 50, which seems to be "complementary to 360" of the MG displayed in R1.... 360-50 (on FDAI ball) = 310 (in R1 in LGC).
Is it normal? if so, I missed so far the correct explanation why it should be so....
FDAI1 issues after alignment.JPG

(by the way, I red in some other posts that to get rid of the RED flags (shown in the picture above) after the RCS Cold test you need to cycle the CWEA cb .... I did it and it worked....)

in the 2nd picture, I loaded another default scenario and I moved a bit the LM out of 0-180-0 attitude to identify better the angles on the FDAI ball, in this case:
Roll about 2 (MG), pitch about 180 (IG) and yaw about 30 (OG) ...but again, when i check the OG/IG/MG in R1/R2/R3 in V16N20 for the way I get 330 and not 30....still its "complementary angle to 360" .... but this time i saw both FDAI running in parallels

FDAI LM and LGC V16N20 readout.JPG


so I am incline to think that I AM DOING SOMETHING WRONG ..... or I miss some basic explanation about how the LM IMU and FDAI angles are displayed.....

I also forgot to add another question (not related to the FDAI but to LM activation check list):

when the time comes to make the AOT star visibility check, keep following the checklists, I entered into the CSM AGC the RPY angles for the visibility check I got from the PAD; I piloted the CSM/LM at that attitude by V49; BUT when the correct GET time come (I think 42:55:00 if I am not mistaken) looking into the AOT (detent F) I saw the Earth below (I saw the Earth during night pass not any stars).
I tried another time, this time I entered the RPY angles as set in the original flight plan, but still when the time came looking outside from the AOT I saw again the Earth below .... and no stars. Lock like I was "rolled" or "yawed" to face with the AOT in, F detent, the EARTH not the SKY and STARS above....
is this normal at this stage of the checklist?
why the PAD angles are different from the flight plan angles?
... by the way, going into external view and pan around with the mouse I could not find SIRIUS as well....

last point: at some point in the checklist it was requesting to look at the stars visible while putting the detent to CL ... when i did it could only see "inside the CSM, towards the LEB facing the SCT/SXT and panel 100-122 so to speak) not to the outside universe....
again, is this normal at this stage of the checklist?

thanks again to read me,
Paolo
bye for now.
 

indy91

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The ATTITUDE MON switches on each side decide which attitude information source to use for the FDAIs. It's either the IMU (PGNS) or coming from the AEA (AGS). Usually you have them aligned to the same angles, but if you do a IMU coarse align with Verb 41 that of course only changes the IMU. 400+3 on the DEDA then does a PGNS to AGS alignment.

The IMU signal to the FDAI goes through the GASTA (Gimbal Angle Sequencing Transformation Assembly) which essentially exchanges yaw and roll, although it's not that simple especially with roll and yaw angles further away from 0. That also means that Noun 20 on the DSKY, which shows the true IMU gimbal angles, won't show the same thing as the PGNS driven FDAI. The LGC can do this IMU to FDAI conversion internally as well. You can play around with that to get a feeling for it with Verb 49. The value you enter for V49 is N22 which are the true IMU angles. When you then PRO to V50 N18 it shows the converted FDAI angles. Use e.g. 180° for yaw or roll in N22 and some other values for the other angles. You will see that it sometimes is an illegal entry and in other cases FDAI and IMU differ quite a bit. The math (https://www.ibiblio.org/apollo/NARA-SW/R-567-sec5-rev8-5.6-end.pdf on PDF pages 76 to 78) is a bit complicated, but it essentially changes the axes of the coordinate system rather than just yaw and roll angles, so it's not always intuitive.

I remember seeing the same AOT issues, but I thought it was only when I was looking at the wrong detent, so not sure what it is going on there...

Regarding the scenario issues, are you all updated on the latest NASSP release? My last big project was updating Apollo 9 to use Sundance for the LGC and I made all new scenarios for it. I'll check if I get the same issues as you had.
 

thermocalc

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thank you Indy91 for your explanations, cannot say I fully understood you right now, but I will try to have a look at the doc you mentioned first and I will try to go on with the LM activation checklists and try some V49 auto-maneuver with the LM...if still have doubts I will go back for new questions....
About the version, I am using Orbiter Beta r90 NASSP v8 1538 ... I saw your post back in Aug.12th when you were talking about your projects, that's why i decided to try Apollo 9 first....actually, according that post you mentioned also that you modified the Saturn IB guidance for Apollo 7....as I am still doing A7 (not arrived to the rendezvous part yet) I was using NASSP v7 on Orbiter 2010P1 as I understood, reading old posts, that NASSP v8 is OK only for later missions, A9-10-11 only. but it had some issues for A7 and A8....is it still so?if you say that A7 in NASSP v8 is fully supported than I would be happy to restart the mission A7 in NASSP v8....thanks.
Paolo.
 

n72.75

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Apollo 7 and 8 should be fine in NASSP 8, as long as you start from the pre-launch -4hr scenarios (the mission scenarios haven't been updated in a while)

I actually just made a minor update to he Apollo 7 checklist so that in the unlikely event that you need to do the NCC2 burn, there's checklist items for it.
 

thermocalc

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@n72.75
thanks, happy to know that, surely I will restart Apollo 7 from scratch with NASSP v8 if you say so (clearly the historical scenarios will be outdated, so for practicing rendezvous if in serious panic I may still jump to the v7 hoping around with the scenarios there before re-attempting the same steps in v8)
I will check if there is new release above 1538 and update immidiatly in case.

@indy91
the doc you sent me was very interesting, it also answer to some other questions related to how to use the AOT for marking stars ... good; i also put the equations of the IMU-FDAI angles transformations in excel and play with the angles to get the feeling, in particular I saw that more or less i get the same FDAI angles R-P-Y observed in the attached files of my previous post above while using the OG/IG/MG LM angles in the PAMFD ... so now i got the point: for the LM the O/I/M angles are not simply the Y-P-R angles but are more complicated stuff .... I also played a little bit with V49, and now I see that putting in N22 the gimbals angles and pressing PRO i got the FDAI R-P-Y angles ... but then this raise the further question: if I need to put the LM in a given orientation I will need to get a given R-P-Y angles but how do I know in advance which O/I/M gimbals angles to request in V49?
MAYBE when time will come to get some PAD I hope to understand better what angles I am suppose to enter, but for the time being I will keep trying to get a better feeling for it.

thanks again to both of you.
Cheers, Paolo
 
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