Source Code
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These source-code files are part of a reconstructed copy of Comanche 051, the
original release of the Apollo 11 Command Module (CM) Apollo Guidance Computer
(AGC) software.
The reconstruction began with source code of Comanche 055 previously transcribed
from a digitized copy of that program. The code was then updated by undoing
changes related to the R-2 lunar potential model, using hints from program
comments and change-indicating asterisks in the Comanche 055 listing as a guide.
The reconstruction was verified by matching memory-bank checksums to those listed
in drawing 2021153D. Note that page numbers in the reconstructed code match those
on the Comanche 055 printout, although the added code would likely have changed page
numbers for a real Comanche 051 listing.
Comments from the original source code are prefixed with a single '#' symbol,
whereas comments added later are prefixed by "##" or "###". Report any errors
noted by creating an
issue report at the Virtual AGC
project's GitHub repository.
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017657,000002: ## Copyright: Public domain.
017658,000003: ## Filename: GIMBAL_LOCK_AVOIDANCE.agc
017659,000004: ## Purpose: A section of Comanche revision 051.
017660,000005: ## It is part of the reconstructed source code for the
017661,000006: ## original release of the flight software for the Command
017662,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
017663,000008: ## The code has been recreated from a copy of Comanche 055. It
017664,000009: ## has been adapted such that the resulting bugger words
017665,000010: ## exactly match those specified for Comanche 51 in NASA drawing
017666,000011: ## 2021153D, which gives relatively high confidence that the
017667,000012: ## reconstruction is correct.
017668,000013: ## Reference: pp. 412-413
017669,000014: ## Assembler: yaYUL
017670,000015: ## Contact: Ron Burkey <info@sandroid.org>.
017671,000016: ## Website: www.ibiblio.org/apollo/index.html
017672,000017: ## Mod history: 2019-07-30 MAS Created from Comanche 55.
017673,000018:
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Page 412
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017675,000020: 15,2000 BANK 15
017676,000021: 22,2000 SETLOC KALCMON1
017677,000022: 22,2000 BANK
017678,000023:
017679,000024: 22,2737 E6,1661 EBANK= BCDU
017680,000025:
017681,000026: # DETECTING GIMBAL LOCK
017682,000027: 22,2737 22,2737 LOCSKIRT EQUALS WCALC
017683,000028: 22,2737 70740 WCALC LXC,1 DLOAD*
017684,000029: 22,2740 01130 RATEINDX
017685,000030: 22,2741 04771 ARATE,1
017686,000031: 22,2742 45002 SR4 CALL # COMPUTE THE INCREMENTAL ROTATION MATRIX
017687,000032: 22,2743 44530 DELCOMP # DEL CORRESPONDING TO A 1 SEC ROTATION
017688,000033: # ABOUT COF
017689,000034: 22,2744 74343 DLOAD* VXSC
017690,000035: 22,2745 04771 ARATE,1
017691,000036: 22,2746 03343 COF
017692,000037: 22,2747 77721 MXV
017693,000038: 22,2750 05003 QUADROT
017694,000039: 22,2751 17311 STODL BRATE
017695,000040: 22,2752 03365 AM
017696,000041: 22,2753 55605 DMP DDV*
017697,000042: 22,2754 05001 ANGLTIME
017698,000043: 22,2755 04771 ARATE,1
017699,000044: 22,2756 77661 SR
017700,000045: 22,2757 20606 5
017701,000046: 22,2760 27317 STOVL TM
017702,000047: 22,2761 03311 BRATE
017703,000048: 22,2762 77761 VXSC
017704,000049: 22,2763 05025 BIASCALE
017705,000050: 22,2764 03275 STORE BIASTEMP # ATTITUDE ERROR BIAS TO PREVENT OVERSHOOT
017706,000051: # IN SYSTEM
017707,000052: 22,2765 77614 SETGO # STATE SWITCH CALCMAN2 (43D)
017708,000053: 22,2766 01035 CALCMAN2 # 0(OFF) = BYPASS STARTING PROCEDURE
017709,000054: 22,2767 45032 NEWANGL +1 # 1(ON) = START MANEUVER
017710,000055:
017711,000056:
017712,000057: 22,2770 00044 15053 ARATE 2DEC .0022222222 # = .05 DEG/SEC
017713,000058:
017714,000059: 22,2772 00221 24255 2DEC .0088888889 # = .2 DEG/SEC
017715,000060:
017716,000061: 22,2774 00554 02660 2DEC .0222222222 # = .5 DEG/SEC
017717,000062:
017718,000063: 22,2776 02660 13301 2DEC .0888888889 # = 2 DEG/SEC $22.5 DEG/SEC
017719,000064:
017720,000065: 22,3000 00003 04000 ANGLTIME 2DEC .000190735 # = 100B - 19
017721,000066:
017722,000067: # MANEUVER ANGLE TO MANEUVER TIME
017723,000068: 22,3002 03146 14632 QUADROT 2DEC .1 # ROTATION MATRIX FROM S/C AXES TO CONTROL
017724,000069:
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Page 413
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017726,000071: 22,3004 00000 00000 2DEC 0 B-28 # AXES (X ROT = -7.25 DEG)
017727,000072:
017728,000073: 22,3006 00000 00000 2DEC 0 B-28
017729,000074:
017730,000075: 22,3010 00000 00000 2DEC 0 B-28
017731,000076:
017732,000077: 22,3012 03131 11275 2DEC .099200 # =(.1)COS7.25
017733,000078:
017734,000079: 22,3014 77461 47370 2DEC -.012620 # =-(.1)SIN7.25
017735,000080:
017736,000081: 22,3016 00000 00000 2DEC 0 B-28
017737,000082:
017738,000083: 22,3020 00316 30407 2DEC .012620 # (.1)SIN7.25
017739,000084:
017740,000085: 22,3022 03131 11275 2DEC .099200 # (.1)COS7.25
017741,000086:
017742,000087: 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