Gimbal Lock

Lupus_Vulpes

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Messing around with Apollo 8 CSM, testing a few CMC features and experimenting a bit... Got the CSM into gimbal lock... What is the procedure to get it out of gimbal lock?
 

indy91

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The AOH Volume 2 has a suggested procedure (https://www.ibiblio.org/apollo/Documents/AOH_A16_VOL2_Part_2.pdf PDF page 302).

V37E 00E
V41 N20E (coarse aligns the IMU to zero angles)
00000E
00000E
00000E
V40 N20E (Makes the No Att light go away)
RSET

And then a new alignment from scratch, so P51 and then P52. After the P51 or P52 there would probably be a REFSMMAT uplink, but it isn't strictly required, not really part of the procedure to recover from the gimbal lock.
 

Lupus_Vulpes

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Thanks for the info, but i have another question, how can i null all my rates to 0 with the CMC, i want to get the CSM as still as possible?
 

Miriam

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You could also try the rapid IMU realign procedure:

Maneuver to 0,0,0 on the GDC FDAI
V41N20E, E,E,E (coarse align to 0,0,0)
V40N20E (fine align; NO ATT lt off)
V25N07E
76E, 40000E, 1E (set DRIFT flag)
V25E
77E, 10000E, 1E (set REFSMMAT flag)
Do a P52 option 3 (Note that auto optics may be off quite a bit and torquing angles may be high, especially in roll. No problem as long as the star angle difference is okay.)
GDC align to IMU

how can i null all my rates to 0 with the CMC, i want to get the CSM as still as possible?
SC CONT - CMC
CMC MODE - HOLD
You should also check the deadband and rates in V48. You'll get the tightest deadband with narrow deadband and lowest rate setting (XXX00 in R2 of N46).
 
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