Source Code
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These source-code files are part of a reconstructed copy of LUM69 Revision 2, the
flown Apollo 10 Lunar Module (LM) Apollo Guidance Computer (AGC) software.
The reconstruction began with source code of Luminary 69 revision 0 previously
transcribed from a digitized copy of that program. The code was then updated
by back-porting the R-2 lunar potential model from previously-transcribed source
code of Luminary 99. These required changes were described in the original
Luminary memos 75 and 78. The reconstructed code was verified by
matching memory-bank checksums to those listed in drawing 2021152G. Note that
page numbers in the reconstructed code match those on the Luminary 069 printout,
although the added code would likely have changed page numbers for a real LUM69
Revision 2 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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016208,000002: ## Copyright: Public domain.
016209,000003: ## Filename: GIMBAL_LOCK_AVOIDANCE.agc
016210,000004: ## Purpose: A section of LUM69 revision 2.
016211,000005: ## It is part of the reconstructed source code for the flown
016212,000006: ## version of the flight software for the Lunar Module's (LM)
016213,000007: ## Apollo Guidance Computer (AGC) for Apollo 10. The code has
016214,000008: ## been recreated from a copy of Luminary revsion 069, using
016215,000009: ## changes present in Luminary 099 which were described in
016216,000010: ## Luminary memos 75 and 78. The code has been adapted such
016217,000011: ## that the resulting bugger words exactly match those specified
016218,000012: ## for LUM69 revision 2 in NASA drawing 2021152B, which gives
016219,000013: ## relatively high confidence that the reconstruction is correct.
016220,000014: ## Reference: p. 377
016221,000015: ## Assembler: yaYUL
016222,000016: ## Contact: Ron Burkey <info@sandroid.org>.
016223,000017: ## Website: www.ibiblio.org/apollo/index.html
016224,000018: ## Mod history: 2019-07-27 MAS Created from Luminary 69.
016225,000019:
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Page 377
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016227,000021: 15,2050 BANK 15
016228,000022:
016229,000023: 22,2000 SETLOC KALCMON1
016230,000024: 22,2000 BANK
016231,000025:
016232,000026: # DETECTING GIMBAL LOCK
016233,000027: 22,2744 22,2744 LOCSKIRT EQUALS NOGIMLOC
016234,000028:
016235,000029: 22,2744 77614 NOGIMLOC SET
016236,000030: 22,2745 01074 CALCMAN3
016237,000031: 22,2746 70740 WCALC LXC,1 DLOAD*
016238,000032: 22,2747 01325 RATEINDX # CHOOSE THE DESIRED MANEUVER RATE
016239,000033: 22,2750 04772 ARATE,1 # FROM A LIST OF FOUR
016240,000034: 22,2751 45002 SR4 CALL # COMPUTE THE INCREMENTAL ROTATION MATRIX
016241,000035: 22,2752 44527 DELCOMP # DEL CORRESPONDING TO A 1 SEC ROTATION
016242,000036: # ABOUT COF
016243,000037: 22,2753 74343 DLOAD* VXSC
016244,000038: 22,2754 04772 ARATE,1
016245,000039: 22,2755 03267 COF
016246,000040: 22,2756 17324 STODL BRATE # COMPONENT MANEUVER RATES 45 DEG/SEC
016247,000041: 22,2757 03334 AM
016248,000042: 22,2760 55605 DMP DDV*
016249,000043: 22,2761 05002 ANGLTIME
016250,000044: 22,2762 04772 ARATE,1
016251,000045: 22,2763 77661 SR
016252,000046: 22,2764 20606 5
016253,000047: 22,2765 03332 STORE TM # MANEUVER EXECUTION TIME SCALED AS T2
016254,000048: 22,2766 77614 SETGO
016255,000049: 22,2767 01035 CALCMAN2 # 0(OFF) = CONTINUE MANEUVER
016256,000050: 22,2770 45010 NEWANGL +1 # 1(ON) = START MANEUVER
016257,000051:
016258,000052: # THE FOUR SELECTABLE FREE FALL MANEUVER RATES SELECTED BY
016259,000053: # LOADING RATEINDX WITH 0, 2, 4, 6, RESPECTIVELY
016260,000054:
016261,000055: 22,2771 00221 24255 ARATE 2DEC .0088888888 # = 0.2 DEG/SEC $ 22.5 DEG/SEC
016262,000056:
016263,000057: 22,2773 00554 02660 2DEC .0222222222 # = 0.5 DEG/SEC $ 22.5 DEG/SEC
016264,000058:
016265,000059: 22,2775 02660 13301 2DEC .0888888888 # = 2.0 DEG/SEC $ 22.5 DEG/SEC
016266,000060:
016267,000061: 22,2777 16161 30707 2DEC .4444444444 # = 10.0 DEG/SEC $ 22.5 DEG/SEC
016268,000062:
016269,000063: 22,3001 00003 04000 ANGLTIME 2DEC .0001907349 # = 100B-19 FUDGE FACTOR TO CONVERT
016270,000064: # MANEUVER ANGLE TO MANEUVER TIME
016271,000065:
016272,000066:
End of include-file GIMBAL_LOCK_AVOIDANCE.agc. Parent file is MAIN.agc