Source Code
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These source-code files are part of a reconstructed copy of Comanche 51, the
initial release (though not the final mission release) of the Apollo 11
Command Module (CM) Apollo Guidance Computer (AGC) software. The flown, final
release was Comanche 55. The reconstruction is believed to be exactly accurate,
but in the absence of an actual Apollo-era listing of Comanche 51, some
explanation of the reconstruction process is needed to insure confidence in
that accuracy.
The starting point was the source code of Comanche 55, whose original source code
is available. Comanche 55 source code was then modified by undoing changes known
to have been made between revisions 51 and 55. The most-significant steps involved
reverting changes related to the R-2 lunar potential model, the details of which
were known from the previous, separate, independent reconstruction of the Apollo 10
Lunar Module software Luminary 69/2. The now-reconstructed
Comanche 51 source code was verified by assembling it and checking that the assembled
code had the expected known-correct memory-bank checksums. Note that page numbers in
the reconstructed code match those on the Comanche 55 or Luminary 69 printouts, although
the source code would likely have different page numbers in a contemporary Comanche 51 listing.
Annotations that were not present in the contemporary source code have been added to
the reconstructed code to justify each change relative to Comanche 55. Here's a guide
to some of the Apollo documentation relevant to those annotations:
Among documentation not actually referenced in the annotations, there is
a short writeup about the reconstruction process in our software repository
that may be helpful in understanding it from a different perspective. There's also
a handy table
that lists what the number of memory-words should be for each routine in Comanche 51,
which could make a nice double-check; however, we've not performed that double-check ourselves.
Comments expected to have been present in 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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041511,000002: ## Copyright: Public domain.
041512,000003: ## Filename: TVCMASSPROP.agc
041513,000004: ## Purpose: A section of Comanche revision 051.
041514,000005: ## It is part of the reconstructed source code for the
041515,000006: ## original release of the flight software for the Command
041516,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
041517,000008: ## The code has been recreated from a copy of Comanche 055. It
041518,000009: ## has been adapted such that the resulting bugger words
041519,000010: ## exactly match those specified for Comanche 51 in NASA drawing
041520,000011: ## 2021153D, which gives relatively high confidence that the
041521,000012: ## reconstruction is correct.
041522,000013: ## Reference: pp. 951-955
041523,000014: ## Assembler: yaYUL
041524,000015: ## Contact: Ron Burkey <info@sandroid.org>.
041525,000016: ## Website: www.ibiblio.org/apollo/index.html
041526,000017: ## Mod history: 2019-07-30 MAS Created from Comanche 55.
041527,000018:
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Page 951
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041529,000020: # PROGRAM NAME....MASSPROP
041530,000021: # LOG SECTION....TVCMASSPROP PROGRAMMER...MELANSON (ENGEL, SCHLUNDT)
041531,000022:
041532,000023: # FUNCTIONAL DESCRIPTION:
041533,000024:
041534,000025: # MASSPROP OPERATES IN TWO MODES: (1) IF LEM MASS OR CONFIGURATION ARE UPDATED (MASSPROP DOES NOT TEST
041535,000026: # FOR THIS) THE ENTIRE PROGRAM MUST BE RUN THROUGH, BREAKPOINT VALUES AND DERIVATIVES OF THE OUTPUTS WITH
041536,000027: # RESPECT TO CSM MASS BEING CALCULATED PRIOR TO CALCULATION OF THE OUTPUTS. (2) OTHERWISE, THE OUTPUTS CAN BE
041537,000028: # CALCULATED USING PREVIOUSLY COMPUTED BREAKPOINT VALUES AND DERIVATIVES.
041538,000029:
041539,000030: # CALLING SEQUENCES
041540,000031:
041541,000032: # IF LEM MASS OR CONFIGURATION HAS BEEN UPDATED, TRANSFER TO MASSPROP, OTHERWISE TRANSFER TO FIXCW.
041542,000033: # L TC BANKCALL OR IBNKCALL
041543,000034: # L+1 CADR MASSPROP
041544,000035: # OR
041545,000036: # L+1 CADR FIXCW
041546,000037: # L+2 RETURNS VIA Q
041547,000038:
041548,000039: # CALLED IN PARTICULAR BY DONOUN47 (JOB) AND TVCEXECUTIVE (TASK)
041549,000040:
041550,000041: # JOBS OR TASKS INITIATED - NONE
041551,000042:
041552,000043: # SUBROUTINES CALLED - NONE
041553,000044:
041554,000045: # ERASABLE INITIALIZATION REQUIRED
041555,000046:
041556,000047: # LEMMASS MUST CONTAIN LEM MASS SCALED AT B+16 IN KILOGRAMS
041557,000048: # CSMMASS MUST CONTAIN CSM MASS SCALED AT B+16 IN KILOGRAMS
041558,000049: # DAPDATR1 MUST BE SET TO INDICATE VEHICLE CONFIGURATION.
041559,000050: # BITS (15,14,13) = ( 0 , 0 , 1 ) LEM OFF
041560,000051: # ( 0 , 1 , 0 ) LEM ON (ASCNT,DSCNT)
041561,000052: # ( 1 , 1 , 0 ) LEM ON (ASCNT ONLY)
041562,000053:
041563,000054: # ALARMS - NONE
041564,000055:
041565,000056: # EXIT - TC Q
041566,000057:
041567,000058: # OUTPUTS:
041568,000059:
041569,000060: # (1) IXX, SINGLE PRECISION SCALED AT B+20 IN KG-M SQ.
041570,000061: # (2) IAVG, SINGLE PRECISION SCALED AT B+20 IN KG-M SQ.
041571,000062: # (3) IAVG/TLX, SINGLE PRECISION, SCALED AT B+2 SEC-SQD
041572,000063: #
041573,000064: # THEY ARE STORED IN CONSECUTIVE REGISTERS IXX0, IXX1, IXX2
041574,000065: # CONVERSION FACTOR: (SLUG-FTSQ) = 0.737562 (KG-MSQ)
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Page 952
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041576,000067:
041577,000068: # OUTPUTS ARE CALCULATED AS FOLLOWS:
041578,000069:
041579,000070: # (1) IF LEM DOCKED, LEMMASS IS FIRST ELIMINATED AS A PARAMETER
041580,000071:
041581,000072: # VARST0 = INTVALUE0 + LEMMASS(SLOPEVAL0) IXX BREAKPOINT VALUE
041582,000073: # VARST1 = INTVALUE1 + LEMMASS(SLOPEVAL1) IAVG BREAKPOINT VALUE
041583,000074: # VARST2 = INTVALUE2 + LEMMASS(SLOPEVAL2) IAVG/TLX BREAKPOINT VALUE
041584,000075:
041585,000076: # VARST3 = INTVALUE3 + LEMMASS(SLOPEVAL3) IAVG/TLX SLOPE FOR CSMMASS > 33956 LBS (SPS > 10000 LBS)
041586,000077: # VARST4 = INTVALUE4 + LEMMASS(SLOPEVAL4) IAVG SLOPE FOR CSMMASS > 33956 LBS (SPS > 10000 LBS)
041587,000078:
041588,000079: # VARST5 = INTVALUE5 + LEMMASS(SLOPEVAL5) IXX SLOPE FOR ALL VALUES OF CSMMASS
041589,000080:
041590,000081: # VARST6 = INTVALUE6 + LEMMASS(SLOPEVAL6) IAVG SLOPE FOR CSMMASS < 33956 LBS (SPS < 10000 LBS)
041591,000082: # VARST7 = INTVALUE7 + LEMMASS(SLOPEVAL7) IAVG/TLX SLOPE FOR CSMMASS < 33956 LBS (SPS < 10000 LBS)
041592,000083:
041593,000084: # VARST8 = INTVALUE8 + LEMMASS(SLOPEVAL8) IAVG DECREMENT TO BRKPT VALUE WHEN LEM DSCNT STAGE OFF
041594,000085: # VARST9 = INTVALUE9 + LEMMASS(SLOPEVAL9) IAVG/TLX DECREMENT TO BRKPT VALUE WHEN LEM DSCNT STAGE OFF
041595,000086:
041596,000087: # (2) IF LEM NOT DOCKED
041597,000088:
041598,000089: # VARST0 = NOLEMVAL0 WHERE THE MEANING AND SCALING OF VARST0
041599,000090: # . . TO VARST9 ARE THE SAME AS GIVEN ABOVE
041600,000091: # . .
041601,000092: # . . NOTE... FOR THIS CASE, VARST8,9 HAVE NO
041602,000093: # VARST9 = NOLEMVAL9 MEANING (THEY ARE COMPUTED BUT NOT USED)
041603,000094:
041604,000095: # (3) THE FINAL OUTPUT CALCULATIONS ARE THEN DONE
041605,000096:
041606,000097: # IXX0 = VARST0 + (CSMMASS + NEGBPW)VARST5 IXX
041607,000098:
041608,000099: # IXX1 = VARST1 + (CSMMASS + NEGBPW)VARST(4 OR 6) IAVG
041609,000100:
041610,000101: # IXX2 = VARST2 + (CSMMASS + NEGBPW)VARST(3 OR 7) IAVG/TLX
041611,000102:
041612,000103: # THE DATA USED CAME FROM CSM/LM SPACECRAFT OPERATIONAL DATA BOOK.
041613,000104: # VOL. 3, NASA DOCUMENT SNA-8-D-027 (MARCH 1968)
041614,000105:
041615,000106: # PERTINENT MASS DATA: CSM WEIGHT (FULL) 64100 LBS
041616,000107: # (EMPTY) 23956 LBS
041617,000108: # LEM WEIGHT (FULL) 32000 LBS
041618,000109: # (EMPTY) 14116 LBS
041619,000110:
041620,000111: # (WEIGHTS ARE FROM AMENDMENT #1 (APRIL 24, 1968) TO ABOVE DATA BOOK)
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Page 953
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041622,000113:
041623,000114: 25,3774 BANK 25
041624,000115: 05,2000 SETLOC DAPMASS
041625,000116: 05,2000 BANK
041626,000117: 05,3366 E6,1702 EBANK= BZERO
041627,000118: 05,3366 COUNT* $$/MASP
041628,000119:
041629,000120: 05,3366 34334 MASSPROP CAF NINE # MASSPROP USES TVC/RCS INTERUPT TEMPS
041630,000121: 05,3367 55506 TS PHI333 # SET UP TEN PASSES
041631,000122:
041632,000123: 05,3370 31466 LEMTEST CAE DAPDATR1 # DETERMINE LEM STATUS
041633,000124: 05,3371 75003 MASK BIT13
041634,000125: 05,3372 00006 EXTEND
041635,000126: 05,3373 13377 BZF LEMYES
041636,000127:
041637,000128: 05,3374 51506 LEMNO INDEX PHI333 # LEM NOT ATTACHED
041638,000129: 05,3375 33463 CAF NOLEMVAL
041639,000130: 05,3376 13407 TCF STOINST
041640,000131:
041641,000132: 05,3377 31473 LEMYES CAE LEMMASS # LEM IS ATTACHED
041642,000133: 05,3400 60000 DOUBLE
041643,000134: 05,3401 00006 EXTEND
041644,000135: 05,3402 51506 INDEX PHI333
041645,000136: 05,3403 73505 MP SLOPEVAL
041646,000137: 05,3404 20001 DDOUBL
041647,000138: 05,3405 51506 INDEX PHI333
041648,000139: 05,3406 63473 AD INTVALUE
041649,000140:
041650,000141: 05,3407 51506 STOINST INDEX PHI333 # STORAGE INST BEGIN HERE
041651,000142: 05,3410 55511 TS VARST0
041652,000143: 05,3411 11506 CCS PHI333 # ARE ALL TEN PASSES COMPLETED
041653,000144: 05,3412 13367 TCF MASSPROP +1 # NO - GO DECREMENT PHI333
041654,000145:
041655,000146: 05,3413 11466 DXTEST CCS DAPDATR1 # IF NEG, BIT15 IS 1, LEM DSCNT STAGE OFF
041656,000147: 05,3414 13422 TCF FIXCW
041657,000148: 05,3415 13422 TCF FIXCW
041658,000149: 05,3416 53522 DXCH VARST0 +8D
041659,000150: 05,3417 21513 DAS VARST0 +1
041660,000151: 05,3420 33520 CA DXITFIX
041661,000152: 05,3421 27520 ADS VARST0 +7
041662,000153:
041663,000154: 05,3422 35016 FIXCW CAF BIT2 # COMPUTATION PHASE BEGINS HERE. SET UP
041664,000155: 05,3423 55506 TS PHI333 # THREE PASSES
041665,000156: 05,3424 55507 TS PSI333
041666,000157:
041667,000158: 05,3425 31474 CAE CSMMASS # GET DELTA CSM WEIGHT - SIGN DETERMINES
041668,000159: 05,3426 63517 AD NEGBPW # SLOPE LOCATIONS.
041669,000160: 05,3427 60000 DOUBLE
041670,000161: 05,3430 55510 TS TEMP333
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Page 954
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041672,000163: 05,3431 00006 EXTEND
041673,000164: 05,3432 63435 BZMF PEGGY # DETERMINE CORRECT SLOPE
041674,000165: 05,3433 37715 CAF NEG2
041675,000166: 05,3434 55506 TS PHI333
041676,000167:
041677,000168: 05,3435 51506 PEGGY INDEX PHI333 # ALL IS READY - CALCULATE OUTPUTS NOW
041678,000169: 05,3436 31516 CAE VARST5 # GET SLOPE
041679,000170: 05,3437 00006 EXTEND
041680,000171: 05,3440 71510 MP TEMP333 # MULT BY DELTA CSM WEIGHT
041681,000172: 05,3441 60000 DOUBLE
041682,000173: 05,3442 51507 INDEX PSI333
041683,000174: 05,3443 61511 AD VARST0 # ADD BREAKPOINT VALUE
041684,000175: 05,3444 51507 INDEX PSI333
041685,000176: 05,3445 55470 TS IXX # ****** OUTPUTS (IXX0, IXX1, IXX2) ******
041686,000177:
041687,000178: 05,3446 11507 CCS PSI333 # BOOKKEEPING - MASSPROP FINISHED OR NOT
041688,000179: 05,3447 13457 TCF BOKKEP2 # NO - GO TAKE CARE OF INDEXING REGISTERS
041689,000180:
041690,000181: 05,3450 31466 CAE DAPDATR1 # UPDATE WEIGHT/G
041691,000182: 05,3451 75002 MASK BIT14
041692,000183: 05,3452 10000 CCS A
041693,000184: 05,3453 31473 CA LEMMASS
041694,000185: 05,3454 61474 AD CSMMASS
041695,000186: 05,3455 55475 TS WEIGHT/G # SCALED AT B+16 IN KILOGRAMS
041696,000187: 05,3456 00002 ENDMASSP TC Q
041697,000188:
041698,000189: 05,3457 55507 BOKKEP2 TS PSI333 # REDUCE PSI BY ONE
041699,000190: 05,3460 00006 EXTEND
041700,000191: 05,3461 27506 DIM PHI333
041701,000192: 05,3462 13435 TCF PEGGY
041702,000193:
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Page 955
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041704,000195: 05,3463 00616 NOLEMVAL DEC 25445 B-20
041705,000196: 05,3464 02526 DEC 87450 B-20
041706,000197: 05,3465 02352 DEC .30715 B-2
041707,000198: 05,3466 01471 DEC 1.22877 E-5 B+12
041708,000199: 05,3467 00634 DEC 1.6096 B-6
041709,000200: 05,3470 00612 DEC 1.54 B-6
041710,000201: 05,3471 03706 DEC 7.77177 B-6
041711,000202: 05,3472 04425 DEC 3.46458 E-5 B+12
041712,000203:
041713,000204: 05,3473 00644 INTVALUE DEC 26850 B-20
041714,000205: 05,3474 03710 DEC 127518 B-20
041715,000206: 05,3475 04246 DEC .54059 B-2
041716,000207: 05,3476 02011 DEC .153964 E-4 B+12
041717,000208: 05,3477 77501 DEC -.742923 B-6
041718,000209: 05,3500 00612 DEC 1.5398 B-6
041719,000210: 05,3501 04656 DEC 9.68 B-6
041720,000211: 05,3502 10372 DEC .647625 E-4 B+12
041721,000212: 05,3503 77126 DEC -27228 B-20
041722,000213: 05,3504 76261 DEC -.206476 B-2
041723,000214:
041724,000215: 05,3505 00767 SLOPEVAL DEC 1.96307 B-6
041725,000216: 05,3506 15624 DEC 27.5774 B-6
041726,000217: 05,3507 03054 DEC 2.3548 E-5 B+12
041727,000218: 05,3510 04532 DEC 2.1777 E-9 B+26
041728,000219: 05,3511 10433 DEC 1.044 E-3 B+8
041729,000220: 05,3512 00000 DEC 0 B-14
041730,000221: 05,3513 22070 DEC 2.21068 E-3 B+8
041731,000222: 05,3514 03204 DEC 1.5166 E-9 B+26
041732,000223: 05,3515 77266 DEC -1.284 B-6
041733,000224: 05,3516 02476 DEC 2 E-5 B+12
041734,000225:
041735,000226: 05,3517 70364 NEGBPW DEC -15402.17 B-16
041736,000227: 05,3520 75420 DXITFIX DEC* -1.88275 E-5 B+12*
041737,000228:
End of include-file TVCMASSPROP.agc. Parent file is MAIN.agc