Source Code
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These source-code files are part of a reconstructed copy of Comanche 72/3 (AKA Manche72 revision 3),
the final, flown mission release of the Apollo Guidance Computer (AGC) Command Module (CM) software
for Apollo 13.
The starting point was the source code of Comanche 72 (itself previously reconstructed). Comanche 72
source code was then modified by incorporating changes known from contemporary documentation to have
been made between revisions 72 and 72/3. The resulting code assembles to have identical
memory-bank checksums as those specified in NASA drawing 2021153G; this gives reasonably
high confidence that the changes that have been made are correct. In places where
ambiguity exists, this ambiguity is discussed in "## Reconstruction:" comments.
Since no contemporary listings of Comanche 72/3 are available as source material,
all comments and labels are approximate.
They have been taken from other AGC programs where possible, or, in some places, written
from scratch to match what we believe would have been in the original listing.
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017416,000002: ## Copyright: Public domain.
017417,000003: ## Filename: GIMBAL_LOCK_AVOIDANCE.agc
017418,000004: ## Purpose: A section of Manche72 revision 3.
017419,000005: ## It is part of the reconstructed source code for the final, flown
017420,000006: ## release of the software for the Command Module's (CM) Apollo
017421,000007: ## Guidance Computer (AGC) for Apollo 13. No original listings
017422,000008: ## of this program are available; instead, this file was recreated
017423,000009: ## from a reconstructed copy of Comanche 072. It has been adapted
017424,000010: ## such that the resulting bugger words exactly match those
017425,000011: ## specified for Manche72 revision 3 in NASA drawing 2021153G,
017426,000012: ## which gives relatively high confidence that the reconstruction
017427,000013: ## is correct.
017428,000014: ## Assembler: yaYUL
017429,000015: ## Contact: Ron Burkey <info@sandroid.org>.
017430,000016: ## Website: www.ibiblio.org/apollo/index.html
017431,000017: ## Mod history: 2024-05-19 MAS Created from Comanche 072.
017432,000018:
017433,000019: 15,2000 BANK 15
017434,000020: 22,2000 SETLOC KALCMON1
017435,000021: 22,2000 BANK
017436,000022:
017437,000023: 22,2737 E6,1661 EBANK= BCDU
017438,000024:
017439,000025: # DETECTING GIMBAL LOCK
017440,000026: 22,2737 22,2737 LOCSKIRT EQUALS WCALC
017441,000027: 22,2737 70740 WCALC LXC,1 DLOAD*
017442,000028: 22,2740 01130 RATEINDX
017443,000029: 22,2741 04771 ARATE,1
017444,000030: 22,2742 45002 SR4 CALL # COMPUTE THE INCREMENTAL ROTATION MATRIX
017445,000031: 22,2743 44530 DELCOMP # DEL CORRESPONDING TO A 1 SEC ROTATION
017446,000032: # ABOUT COF
017447,000033: 22,2744 74343 DLOAD* VXSC
017448,000034: 22,2745 04771 ARATE,1
017449,000035: 22,2746 03343 COF
017450,000036: 22,2747 77721 MXV
017451,000037: 22,2750 05003 QUADROT
017452,000038: 22,2751 17311 STODL BRATE
017453,000039: 22,2752 03365 AM
017454,000040: 22,2753 55605 DMP DDV*
017455,000041: 22,2754 05001 ANGLTIME
017456,000042: 22,2755 04771 ARATE,1
017457,000043: 22,2756 77661 SR
017458,000044: 22,2757 20606 5
017459,000045: 22,2760 27317 STOVL TM
017460,000046: 22,2761 03311 BRATE
017461,000047: 22,2762 77761 VXSC
017462,000048: 22,2763 05025 BIASCALE
017463,000049: 22,2764 03275 STORE BIASTEMP # ATTITUDE ERROR BIAS TO PREVENT OVERSHOOT
017464,000050: # IN SYSTEM
017465,000051: 22,2765 77614 SETGO # STATE SWITCH CALCMAN2 (43D)
017466,000052: 22,2766 01035 CALCMAN2 # 0(OFF) = BYPASS STARTING PROCEDURE
017467,000053: 22,2767 45032 NEWANGL +1 # 1(ON) = START MANEUVER
017468,000054:
017469,000055:
017470,000056: 22,2770 00044 15053 ARATE 2DEC .0022222222 # = .05 DEG/SEC
017471,000057:
017472,000058: 22,2772 00221 24255 2DEC .0088888889 # = .2 DEG/SEC
017473,000059:
017474,000060: 22,2774 00554 02660 2DEC .0222222222 # = .5 DEG/SEC
017475,000061:
017476,000062: 22,2776 02660 13301 2DEC .0888888889 # = 2 DEG/SEC $22.5 DEG/SEC
017477,000063:
017478,000064: 22,3000 00003 04000 ANGLTIME 2DEC .000190735 # = 100B - 19
017479,000065:
017480,000066: # MANEUVER ANGLE TO MANEUVER TIME
017481,000067: 22,3002 03146 14632 QUADROT 2DEC .1 # ROTATION MATRIX FROM S/C AXES TO CONTROL
017482,000068:
017483,000069: 22,3004 00000 00000 2DEC 0 B-28 # AXES (X ROT = -7.25 DEG)
017484,000070:
017485,000071: 22,3006 00000 00000 2DEC 0 B-28
017486,000072:
017487,000073: 22,3010 00000 00000 2DEC 0 B-28
017488,000074:
017489,000075: 22,3012 03131 11275 2DEC .099200 # =(.1)COS7.25
017490,000076:
017491,000077: 22,3014 77461 47370 2DEC -.012620 # =-(.1)SIN7.25
017492,000078:
017493,000079: 22,3016 00000 00000 2DEC 0 B-28
017494,000080:
017495,000081: 22,3020 00316 30407 2DEC .012620 # (.1)SIN7.25
017496,000082:
017497,000083: 22,3022 03131 11275 2DEC .099200 # (.1)COS7.25
017498,000084:
017499,000085: 22,3024 00004 05253 BIASCALE 2DEC .0002543132 # = (450/180)(1/0.6)(1/16384)
End of include-file GIMBAL_LOCK_AVOIDANCE.agc. Parent file is MAIN.agc