Source Code

These source-code files are part of a reconstructed copy of Comanche 45, the second release, though not the final mission release, of the Apollo 10 Command Module (CM) Apollo Guidance Computer (AGC) software. Comanche 45 was preceded by Comanche 44 and followed by Comanche 45/2 (the flown release). The reconstruction is believed to be exactly accurate, but in the absence of an actual Apollo-era listing of Comanche 45, some explanation of the reconstruction process is needed to insure confidence in that accuracy.

The starting point was the source code of Comanche 44 (itself previously accurately reconstructed). Comanche 44 source code was then modified by incorporating changes known from contemporary documentation to have been made between revisions 44 and 45. The now-reconstructed Comanche 45 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 tend to match those in the Comanche 55, the most-similar revision of Comanche for which we have access to an actual non-reconstructed hardcopy; the source code would likely have different page numbers in a contemporary Comanche 45 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 44. Here's a guide to the Apollo documentation referenced in those annotations:
There is also a detailed commentary about the reconstruction process.

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.

057673,000002:                                                                                                  ## Copyright:   Public domain.
057674,000003:                                                                                                  ## Filename:    INFLIGHT_ALIGNMENT_ROUTINES.agc
057675,000004:                                                                                                  ## Purpose:     A section of Comanche revision 045.
057676,000005:                                                                                                  ##              It is part of the reconstructed source code for the
057677,000006:                                                                                                  ##              second release of the flight software for the Command
057678,000007:                                                                                                  ##              Module's (CM) Apollo Guidance Computer (AGC) for Apollo 10.
057679,000008:                                                                                                  ##              The code has been recreated from a copy of Comanche 055. It
057680,000009:                                                                                                  ##              has been adapted such that the resulting bugger words
057681,000010:                                                                                                  ##              exactly match those specified for Comanche 45 in NASA drawing
057682,000011:                                                                                                  ##              2021153D, which gives relatively high confidence that the
057683,000012:                                                                                                  ##              reconstruction is correct.
057684,000013:                                                                                                  ## Assembler:   yaYUL
057685,000014:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
057686,000015:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
057687,000016:                                                                                                  ## Mod history: 2020-12-06 MAS  Created from Comanche 44.
057688,000017: 

Page 1355

057690,000019: 22,3510                                           BANK     22                                    
057691,000020: 23,2000                                           SETLOC   INFLIGHT                              
057692,000021: 23,2000                                           BANK                                           
057693,000022: 
057694,000023: 23,3205  E5,1671                                  EBANK=   XSM                                   
057695,000024: 
057696,000025:                                                                                                  #  CALCGTA COMPUTES THE GYRO TORQUE ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
057697,000026: 
057698,000027:                                                                                                  #  THE INPUT IS THE DESIRED STABLE MEMBER COORDINATES REFERRED TO PRESENT STABLE MEMBER COORDINATES.  THE THREE
057699,000028:                                                                                                  #  HALF-UNIT VECTORS ARE STORED AT XDC, YDC, AND ZDC.
057700,000029: 
057701,000030:                                                                                                  #  THE OUTPUTS ARE THE THREE GYRO TORQUING ANGLES TO BE APPLIED TO THE Y, Z, AND X GYROS AND ARE STORED DP AT IGC,
057702,000031:                                                                                                  #  MGC, AND OGC RESPECTIVELY.
057703,000032: 
057704,000033: 23,3205                                           COUNT    23/INFLT                              
057705,000034: 
057706,000035: 23,3205           71220        CALCGTA            ITA      DLOAD                                 #  PUSHDOWN 00-03, 16D-27D, 34D-37D
057707,000036: 23,3206           00051                                    S2                                    #  XDC = (XD1 XD2 XD3)
057708,000037: 23,3207           02714                                    XDC                                   #  YDC = (YD1 YD2 YD3)
057709,000038: 23,3210           65325                           PDDL     PDDL                                  #  ZDC = (ZD1 ZD2 ZD3)
057710,000039: 23,3211           15335                                    HI6ZEROS                              
057711,000040: 23,3212           02720                                    XDC        +4                         
057712,000041: 23,3213           55476                           DCOMP    VDEF                                  
057713,000042: 23,3214           77656                           UNIT                                           
057714,000043: 23,3215           14027                           STODL    ZPRIME                                #  ZP = UNIT(-XD3 0 XD1) = (ZP1 ZP2 ZP3)
057715,000044: 23,3216           00027                                    ZPRIME                                
057716,000045: 
057717,000046: 23,3217           77742                           SR1                                            
057718,000047: 23,3220           14023                           STODL    SINTH                                 #  SIN(IGC) = ZP1
057719,000048: 23,3221           00033                                    ZPRIME     +4                         
057720,000049: 23,3222           77742                           SR1                                            
057721,000050: 23,3223           34021                           STCALL   COSTH                                 #  COS(IGC) = ZP3
057722,000051: 23,3224           47256                                    ARCTRIG                               
057723,000052: 
057724,000053: 23,3225           16762                           STODL    IGC                                   #  Y GYRO TORQUING ANGLE   FRACTION OF REV.
057725,000054: 23,3226           02716                                    XDC        +2                         
057726,000055: 23,3227           77742                           SR1                                            
057727,000056: 23,3230           14023                           STODL    SINTH                                 #  SIN(MGC) = XD2
057728,000057: 23,3231           00027                                    ZPRIME                                
057729,000058: 
057730,000059: 23,3232           65205                           DMP      PDDL                                  
057731,000060: 23,3233           02720                                    XDC        +4                         #  PD00 = (ZP1)(XD3)
057732,000061: 23,3234           00033                                    ZPRIME     +4                         
057733,000062: 
057734,000063: 23,3235           45205                           DMP      DSU                                   
057735,000064: 23,3236           02714                                    XDC                                   #  MPAC = (ZP3)(XD1)
057736,000065: 23,3237           77626                           STADR                                          
057737,000066: 23,3240           43756                           STCALL   COSTH                                 #  COS(MGC) = MPAC - PD00
057738,000067: 23,3241           47256                                    ARCTRIG                               

Page 1356

057740,000069: 23,3242           26764                           STOVL    MGC                                   #  Z GYRO TORQUING ANGLE   FRACTION OF REV.
057741,000070: 23,3243           00027                                    ZPRIME                                
057742,000071: 23,3244           77641                           DOT                                            
057743,000072: 23,3245           02730                                    ZDC                                   
057744,000073: 23,3246           24021                           STOVL    COSTH                                 #  COS(OGC) = ZP . ZDC
057745,000074: 23,3247           00027                                    ZPRIME                                
057746,000075: 23,3250           77641                           DOT                                            
057747,000076: 23,3251           02722                                    YDC                                   
057748,000077: 23,3252           34023                           STCALL   SINTH                                 #  SIN(OGC) = ZP . YDC
057749,000078: 23,3253           47256                                    ARCTRIG                               
057750,000079: 
057751,000080: 23,3254           36760                           STCALL   OGC                                   #  X GYRO TORQUING ANGLE   FRACTION OF REV.
057752,000081: 23,3255           00051                                    S2                                    
057753,000082: 

Page 1357

057755,000084:                                                                                                  #  ARCTRIG COMPUTES AN ANGLE GIVEN THE SINE AND COSINE OF THIS ANGLE.
057756,000085: 
057757,000086:                                                                                                  #  THE INPUTS ARE SIN/4 AND COS/4 STORED DP AT SINTH AND COSTH.
057758,000087: 
057759,000088:                                                                                                  #  THE OUTPUT IS THE CALCULATED ANGLE BETWEEN +.5 AND -.5 REVOLUTIONS AND STORED AT THETA.  THE OUTPUT IS ALSO
057760,000089:                                                                                                  #  AVAILABLE AT MPAC.
057761,000090: 
057762,000091: 23,3256           51545        ARCTRIG            DLOAD    ABS                                   #  PUSHDOWN  16D-21D
057763,000092: 23,3257           00023                                    SINTH                                 
057764,000093: 23,3260           50025                           DSU      BMN                                   
057765,000094: 23,3261           07474                                    QTSN45                                #  ABS(SIN/4) - SIN(45)/4
057766,000095: 23,3262           47271                                    TRIG1                                 #  IF (-45,45) OR (135,-135)
057767,000096: 
057768,000097: 23,3263           72545                           DLOAD    SL1                                   #  (45,135) OR (-135,-45)
057769,000098: 23,3264           00021                                    COSTH                                 
057770,000099: 23,3265           75326                           ACOS     SIGN                                  
057771,000100: 23,3266           00023                                    SINTH                                 
057772,000101: 23,3267           00025                           STORE    THETA                                 #  X = ARCCOS(COS) WITH SIGN(SIN)
057773,000102: 23,3270           77616                           RVQ                                            
057774,000103: 
057775,000104: 23,3271           72545        TRIG1              DLOAD    SL1                                   #  (-45,45) OR (135,-135)
057776,000105: 23,3272           00023                                    SINTH                                 
057777,000106: 23,3273           77736                           ASIN                                           
057778,000107: 23,3274           14025                           STODL    THETA                                 #  X = ARCSIN(SIN) WITH SIGN(SIN)
057779,000108: 23,3275           00021                                    COSTH                                 
057780,000109: 23,3276           77640                           BMN                                            
057781,000110: 23,3277           47302                                    TRIG2                                 #  IF (135,-135)
057782,000111: 
057783,000112: 23,3300           43545                           DLOAD    RVQ                                   
057784,000113: 23,3301           00025                                    THETA                                 #  X = ARCSIN(SIN)   (-45,45)
057785,000114: 
057786,000115: 23,3302           75345        TRIG2              DLOAD    SIGN                                  #  (135,-135)
057787,000116: 23,3303           15333                                    HIDPHALF                              
057788,000117: 23,3304           00023                                    SINTH                                 
057789,000118: 23,3305           77625                           DSU                                            
057790,000119: 23,3306           00025                                    THETA                                 
057791,000120: 23,3307           00025                           STORE    THETA                                 #  X = .5 WITH SIGN(SIN) - ARCSIN(SIN)
057792,000121: 23,3310           77616                           RVQ                                            #        (+) - (+) OR (-) - (-)
057793,000122: 

Page 1358

057795,000124:                                                                                                  #  SMNB, NBSM, AND AXISROT, WHICH USED TO APPEAR HERE, HAVE BEEN
057796,000125:                                                                                                  #  COMBINED IN A ROUTINE CALLED AX*SR*T, WHICH APPEARS AMONG THE POWERED
057797,000126:                                                                                                  #  FLIGHT SUBROUTINES.
057798,000127: 

Page 1359

057800,000129:                                                                                                  #  CALCGA COMPUTES THE CDU DRIVING ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
057801,000130: 
057802,000131:                                                                                                  #  THE INPUTS ARE  1) THE NAVIGATION BASE COORDINATES REFERRED TO ANY COORDINATE SYSTEM.  THE THREE HALF-UNIT
057803,000132:                                                                                                  #  VECTORS ARE STORED AT XNB, YNB, AND ZNB.  2) THE DESIRED STABLE MEMBER COORDINATES REFERRED TO THE SAME
057804,000133:                                                                                                  #  COORDINATE SYSTEM ARE STORED AT XSM, YSM, AND ZSM.
057805,000134: 
057806,000135:                                                                                                  #  THE OUTPUTS ARE THE THREE CDU DRIVING ANGLES AND ARE STORED SP AT THETAD, THETAD +1, AND THETAD +2.
057807,000136: 
057808,000137: 23,3311           77601        CALCGA             SETPD                                          #  PUSHDOWN 00-05, 16D-21D, 34D-37D
057809,000138: 23,3312           00001                                    0                                     
057810,000139: 23,3313           47375                           VLOAD    VXV                                   
057811,000140: 23,3314           02714                                    XNB                                   #  XNB = OGA (OUTER GIMBAL AXIS)
057812,000141: 23,3315           02700                                    YSM                                   #  YSM = IGA (INNER GIMBAL AXIS)
057813,000142: 23,3316           41456                           UNIT     PUSH                                  #  PD0 = UNIT(OGA X IGA) = MGA
057814,000143: 
057815,000144: 23,3317           44041                           DOT      ITA                                   
057816,000145: 23,3320           02730                                    ZNB                                   
057817,000146: 23,3321           00051                                    S2                                    
057818,000147: 23,3322           24021                           STOVL    COSTH                                 #  COS(OG) = MGA . ZNB
057819,000148: 23,3323           00001                                    0                                     
057820,000149: 23,3324           77641                           DOT                                            
057821,000150: 23,3325           02722                                    YNB                                   
057822,000151: 23,3326           34023                           STCALL   SINTH                                 #  SIN(OG) = MGA . YNB
057823,000152: 23,3327           47256                                    ARCTRIG                               
057824,000153: 23,3330           26760                           STOVL    OGC                                   
057825,000154: 23,3331           00001                                    0                                     
057826,000155: 
057827,000156: 23,3332           50235                           VXV      DOT                                   #  PROVISION FOR MG ANGLE OF 90 DEGREES
057828,000157: 23,3333           02714                                    XNB                                   
057829,000158: 23,3334           02700                                    YSM                                   
057830,000159: 23,3335           77752                           SL1                                            
057831,000160: 23,3336           24021                           STOVL    COSTH                                 #  COS(MG) = IGA . (MGA X OGA)
057832,000161: 23,3337           02700                                    YSM                                   
057833,000162: 23,3340           77641                           DOT                                            
057834,000163: 23,3341           02714                                    XNB                                   
057835,000164: 23,3342           34023                           STCALL   SINTH                                 #  SIN(MG) = IGA . OGA
057836,000165: 23,3343           47256                                    ARCTRIG                               
057837,000166: 23,3344           02764                           STORE    MGC                                   
057838,000167: 
057839,000168: 23,3345           45246                           ABS      DSU                                   
057840,000169: 23,3346           07476                                    .166...                               
057841,000170: 23,3347           77644                           BPL                                            
057842,000171: 23,3350           47371                                    GIMLOCK1                              #  IF ANGLE GREATER THAN 60 DEGREES
057843,000172: 
057844,000173: 23,3351           50375        CALCGA1            VLOAD    DOT                                   
057845,000174: 23,3352           02706                                    ZSM                                   
057846,000175: 23,3353           00001                                    0                                     
057847,000176: 23,3354           24021                           STOVL    COSTH                                 #  COS(IG) = ZSM . MGA
057848,000177: 23,3355           02672                                    XSM                                   

Page 1360

057850,000179: 23,3356           45441                           DOT      STADR                                 
057851,000180: 23,3357           43754                           STCALL   SINTH                                 #  SIN(IG) = XSM . MGA
057852,000181: 23,3360           47256                                    ARCTRIG                               
057853,000182: 
057854,000183: 23,3361           26762                           STOVL    IGC                                   
057855,000184: 23,3362           02760                                    OGC                                   
057856,000185: 23,3363           43034                           RTB      BONCLR                                
057857,000186: 23,3364           45552                                    V1STO2S                               
057858,000187: 23,3365           00200                                    CPHIFLAG                              
057859,000188: 23,3366           00051                                    S2                                    
057860,000189: 23,3367           35156                           STCALL   THETAD                                
057861,000190: 23,3370           00051                                    S2                                    
057862,000191: 
057863,000192: 23,3371           77776        GIMLOCK1           EXIT                                           
057864,000193: 23,3372           05650                           TC       ALARM                                 
057865,000194: 23,3373           00401                           OCT      00401                                 
057866,000195: 23,3374           05546                           TC       UPFLAG                                #  GIMBAL LOCK HAS OCCURED
057867,000196: 23,3375           00056                           ADRES    GLOKFAIL                              
057868,000197: 
057869,000198: 23,3376           06006                           TC       INTPRET                               
057870,000199: 23,3377           77650                           GOTO                                           
057871,000200: 23,3400           47351                                    CALCGA1                               
057872,000201: 

Page 1361

057874,000203:                                                                                                  #  AXISGEN COMPUTES THE COORDINATES OF ONE COORDINATE SYSTEM REFERRED TO ANOTHER COORDINATE SYSTEM.
057875,000204: 
057876,000205:                                                                                                  #  THE INPUTS ARE  1) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM A STORED AT STARAD.  2) THE STAR2 VECTOR
057877,000206:                                                                                                  #  REFERRED TO COORDINATE SYSTEM A STORED AT STARAD +6.  3) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM B STORED
057878,000207:                                                                                                  #  AT LOCATION 6 OF THE VAC AREA.  4) THE STAR2 VECTOR REFERRED TO COORDINATE SYSTEM B STORED AT LOCATION 12D OF
057879,000208:                                                                                                  #  THE VAC AREA.
057880,000209: 
057881,000210:                                                                                                  #  THE OUTPUT DEFINES COORDINATE SYSTEM A REFERRED TO COORDINATE SYSTEM B.  THE THREE HALF-UNIT VECTORS ARE STORED
057882,000211:                                                                                                  #  AT LOCATIONS XDC, XDC +6, XDC +12D, AND STARAD, STARAD +6, STARAD +12D.
057883,000212: 
057884,000213: 23,3401           66370        AXISGEN            AXT,1    SSP                                   #  PUSHDOWN 00-30D, 34D-37D
057885,000214: 23,3402           02743                                    STARAD     +6                         
057886,000215: 23,3403           00051                                    S1                                    
057887,000216: 23,3404           02727                                    STARAD     -6                         
057888,000217: 
057889,000218: 23,3405           77601                           SETPD                                          
057890,000219: 23,3406           00001                                    0                                     
057891,000220: 23,3407           46773        AXISGEN1           VLOAD*   VXV*                                  #  06D   UA = S1
057892,000221: 23,3410           02752                                    STARAD     +12D,1                     #        STARAD +00D     UB = S1
057893,000222: 23,3411           02760                                    STARAD     +18D,1                     
057894,000223: 23,3412           77656                           UNIT                                           #  12D   VA = UNIT(S1 X S2)
057895,000224: 23,3413           06760                           STORE    STARAD     +18D,1                     #        STARAD +06D     VB = UNIT(S1 X S2)
057896,000225: 23,3414           77773                           VLOAD*                                         
057897,000226: 23,3415           02752                                    STARAD     +12D,1                     
057898,000227: 
057899,000228: 23,3416           76433                           VXV*     VSL1                                  
057900,000229: 23,3417           02760                                    STARAD     +18D,1                     #  18D   WA = UA X VA
057901,000230: 23,3420           06766                           STORE    STARAD     +24D,1                     #        STARAD +12D     WB = UB X VB
057902,000231: 
057903,000232: 23,3421           77700                           TIX,1                                          
057904,000233: 23,3422           47407                                    AXISGEN1                              
057905,000234: 
057906,000235: 23,3423           66160                           AXC,1    SXA,1                                 
057907,000236: 23,3424           00006                                    6                                     
057908,000237: 23,3425           00036                                    30D                                   
057909,000238: 
057910,000239: 23,3426           66370                           AXT,1    SSP                                   
057911,000240: 23,3427           00022                                    18D                                   
057912,000241: 23,3430           00051                                    S1                                    
057913,000242: 23,3431           00006                                    6                                     
057914,000243: 
057915,000244: 23,3432           66374                           AXT,2    SSP                                   
057916,000245: 23,3433           00006                                    6                                     
057917,000246: 23,3434           00052                                    S2                                    
057918,000247: 23,3435           00002                                    2                                     
057919,000248: 
057920,000249: 23,3436           76720        AXISGEN2           XCHX,1   VLOAD*                                
057921,000250: 23,3437           00036                                    30D                                   #  X1=-6 X2=+6   X1=-6 X2=+4     X1=-6 X2=+2
057922,000251: 23,3440           00001                                    0,1                                   
057923,000252: 

Page 1362

057925,000254: 23,3441           62757                           VXSC*    PDVL*                                 #  J=(UA)(UB1)   J=(UA)(UB2)     J=(UA)(UB3)
057926,000255: 23,3442           75033                                    STARAD     +6,2                       
057927,000256: 23,3443           00007                                    6,1                                   
057928,000257: 23,3444           77757                           VXSC*                                          
057929,000258: 23,3445           75025                                    STARAD     +12D,2                     
057930,000259: 23,3446           30031                           STOVL*   24D                                   #  K=(VA)(VB1)   J=(VA)(VB2)     J=(VA)(VB3)
057931,000260: 23,3447           00015                                    12D,1                                 
057932,000261: 
057933,000262: 23,3450           53357                           VXSC*    VAD                                   
057934,000263: 23,3451           75017                                    STARAD     +18D,2                     #  L=(WA)(WB1)   J=(WA)(WB2)     J=(WA)(WB3)
057935,000264: 23,3452           76455                           VAD      VSL1                                  
057936,000265: 23,3453           00031                                    24D                                   
057937,000266: 23,3454           53520                           XCHX,1   UNIT                                  
057938,000267: 23,3455           00036                                    30D                                   
057939,000268: 23,3456           06736                           STORE    XDC        +18D,1                     #  XDC = L+J+K   YDC = L+J+K     ZDC = L+J+K
057940,000269: 
057941,000270: 23,3457           77700                           TIX,1                                          
057942,000271: 23,3460           47461                                    AXISGEN3                              
057943,000272: 
057944,000273: 23,3461           77704        AXISGEN3           TIX,2                                          
057945,000274: 23,3462           47436                                    AXISGEN2                              
057946,000275: 
057947,000276: 23,3463           77775                           VLOAD                                          
057948,000277: 23,3464           02714                                    XDC                                   
057949,000278: 23,3465           26736                           STOVL    STARAD                                
057950,000279: 23,3466           02722                                    YDC                                   
057951,000280: 23,3467           26744                           STOVL    STARAD     +6                         
057952,000281: 23,3470           02730                                    ZDC                                   
057953,000282: 23,3471           02752                           STORE    STARAD     +12D                       
057954,000283: 
057955,000284: 23,3472           77616                           RVQ                                            
057956,000285: 

Page 1363

057958,000287: 23,3473           05520 26075  QTSN45             2DEC     .1768                                 
057959,000288: 23,3475           05252 25253  .166...            2DEC     .1666666667                            
057960,000289: 

Page 1364 This page is empty.

057963,000292: 
057964,000293: 
057965,000294: 

End of include-file INFLIGHT_ALIGNMENT_ROUTINES.agc.  Parent file is MAIN.agc