Source Code
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These source-code files are part of a reconstructed copy of Comanche 72, the
first release of the Apollo Guidance Computer (AGC) Command Module (CM) software
for Apollo 13.
They have been adapted from sources files created from a listing of Comanche 55.
These source files were updated to match binary dumps of a set of Comanche 67 rope modules.
They were then further modified by applying known changes between Comanche 67 and Comanche 72.
A binary dump of module B2 of Comanche 72, part number 2010802-021, was also used
to validate changes made to banks 05-13. 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 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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017441,000002: ## Copyright: Public domain.
017442,000003: ## Filename: GIMBAL_LOCK_AVOIDANCE.agc
017443,000004: ## Purpose: A section of Comanche revision 072.
017444,000005: ## It is part of the reconstructed source code for the first
017445,000006: ## release of the software for the Command Module's (CM) Apollo
017446,000007: ## Guidance Computer (AGC) for Apollo 13. No original listings
017447,000008: ## of this program are available; instead, this file was recreated
017448,000009: ## from a printout of Comanche 055, binary dumps of a set of
017449,000010: ## Comanche 067 rope modules, and changelogs between Comanche 067
017450,000011: ## and 072. It has been adapted such that the resulting bugger words
017451,000012: ## exactly match those specified for Comanche 072 in NASA drawing
017452,000013: ## 2021153G, which gives relatively high confidence that the
017453,000014: ## reconstruction is correct.
017454,000015: ## Assembler: yaYUL
017455,000016: ## Contact: Ron Burkey <info@sandroid.org>.
017456,000017: ## Website: www.ibiblio.org/apollo/index.html
017457,000018: ## Mod history: 2024-05-13 MAS Created from Comanche 067.
017458,000019:
017459,000020: 15,2000 BANK 15
017460,000021: 22,2000 SETLOC KALCMON1
017461,000022: 22,2000 BANK
017462,000023:
017463,000024: 22,2737 E6,1661 EBANK= BCDU
017464,000025:
017465,000026: # DETECTING GIMBAL LOCK
017466,000027: 22,2737 22,2737 LOCSKIRT EQUALS WCALC
017467,000028: 22,2737 70740 WCALC LXC,1 DLOAD*
017468,000029: 22,2740 01130 RATEINDX
017469,000030: 22,2741 04771 ARATE,1
017470,000031: 22,2742 45002 SR4 CALL # COMPUTE THE INCREMENTAL ROTATION MATRIX
017471,000032: 22,2743 44530 DELCOMP # DEL CORRESPONDING TO A 1 SEC ROTATION
017472,000033: # ABOUT COF
017473,000034: 22,2744 74343 DLOAD* VXSC
017474,000035: 22,2745 04771 ARATE,1
017475,000036: 22,2746 03343 COF
017476,000037: 22,2747 77721 MXV
017477,000038: 22,2750 05003 QUADROT
017478,000039: 22,2751 17311 STODL BRATE
017479,000040: 22,2752 03365 AM
017480,000041: 22,2753 55605 DMP DDV*
017481,000042: 22,2754 05001 ANGLTIME
017482,000043: 22,2755 04771 ARATE,1
017483,000044: 22,2756 77661 SR
017484,000045: 22,2757 20606 5
017485,000046: 22,2760 27317 STOVL TM
017486,000047: 22,2761 03311 BRATE
017487,000048: 22,2762 77761 VXSC
017488,000049: 22,2763 05025 BIASCALE
017489,000050: 22,2764 03275 STORE BIASTEMP # ATTITUDE ERROR BIAS TO PREVENT OVERSHOOT
017490,000051: # IN SYSTEM
017491,000052: 22,2765 77614 SETGO # STATE SWITCH CALCMAN2 (43D)
017492,000053: 22,2766 01035 CALCMAN2 # 0(OFF) = BYPASS STARTING PROCEDURE
017493,000054: 22,2767 45032 NEWANGL +1 # 1(ON) = START MANEUVER
017494,000055:
017495,000056:
017496,000057: 22,2770 00044 15053 ARATE 2DEC .0022222222 # = .05 DEG/SEC
017497,000058:
017498,000059: 22,2772 00221 24255 2DEC .0088888889 # = .2 DEG/SEC
017499,000060:
017500,000061: 22,2774 00554 02660 2DEC .0222222222 # = .5 DEG/SEC
017501,000062:
017502,000063: 22,2776 02660 13301 2DEC .0888888889 # = 2 DEG/SEC $22.5 DEG/SEC
017503,000064:
017504,000065: 22,3000 00003 04000 ANGLTIME 2DEC .000190735 # = 100B - 19
017505,000066:
017506,000067: # MANEUVER ANGLE TO MANEUVER TIME
017507,000068: 22,3002 03146 14632 QUADROT 2DEC .1 # ROTATION MATRIX FROM S/C AXES TO CONTROL
017508,000069:
017509,000070: 22,3004 00000 00000 2DEC 0 B-28 # AXES (X ROT = -7.25 DEG)
017510,000071:
017511,000072: 22,3006 00000 00000 2DEC 0 B-28
017512,000073:
017513,000074: 22,3010 00000 00000 2DEC 0 B-28
017514,000075:
017515,000076: 22,3012 03131 11275 2DEC .099200 # =(.1)COS7.25
017516,000077:
017517,000078: 22,3014 77461 47370 2DEC -.012620 # =-(.1)SIN7.25
017518,000079:
017519,000080: 22,3016 00000 00000 2DEC 0 B-28
017520,000081:
017521,000082: 22,3020 00316 30407 2DEC .012620 # (.1)SIN7.25
017522,000083:
017523,000084: 22,3022 03131 11275 2DEC .099200 # (.1)COS7.25
017524,000085:
017525,000086: 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