Source Code
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This is the source-code for the Apollo 9 Command Module's Guidance Computer.
These files were derived originally from the scan from MIT's Dibner Institute's
now-discontinued website titled "History of Recent Science and Technology", which
in turn was originally created by Gary Neff, though his high-quality scans were
unfortunately reduced in legibility when presented online.
The markings on the front of the
printout imply that it was the original AGC developer Norm Brodeur's copy.
A scan by Ron Burkey has superceded it, made from a more-legible copy from the collection of original
AGC developer Fred Martin. The source code was transcribed from
those images by Ron Burkey. Note that the page images
presented online are of reduced quality, and that higher-quality images
are available. Report any conversion errors or legibility
problems in page images to info@sandroid.org.
Notations on the program listing read, in part:ASSEMBLE REVISION 249 OF AGC PROGRAM COLOSSUS BY NASA 2021111-041 20'35 OCT. 28,1968Note that the date is the date of the printout, not the date of the program revision. |
035330,000002: ## Copyright: Public domain.
035331,000003: ## Filename: ENTRY_LEXICON.agc
035332,000004: ## Purpose: Part of the source code for Colossus, build 249.
035333,000005: ## It is part of the source code for the Command Module's (CM)
035334,000006: ## Apollo Guidance Computer (AGC), for Apollo 9.
035335,000007: ## Assembler: yaYUL
035336,000008: ## Reference: pp. 791-797.
035337,000009: ## Contact: Ron Burkey <info@sandroid.org>.
035338,000010: ## Website: www.ibiblio.org/apollo.
035339,000011: ## Mod history: 08/19/04 RSB. Transcribed .
035340,000012: ## 2017-01-06 RSB Page numbers now agree with those on the
035341,000013: ## original harcopy, as opposed to the PDF page
035342,000014: ## numbers in 1701.pdf.
035343,000015: ## 2017-01-07 RSB Cross-diff'd comment text (not whitespace)
035344,000016: ## vs the already-proofed corresponding Colossus
035345,000017: ## 237 and Comanche 55 source-code files
035346,000018: ## and corrected errors found.
035347,000019: ## 2017-01-22 RSB Back-ported comment error fixes detected in diff'ing
035348,000020: ## Artemis 72 vs Comanche 55.
035349,000021: ##
035350,000022: ## The contents of the "Colossus249" files, in general, are transcribed
035351,000023: ## from a scanned copy of the program listing. Notations on this
035352,000024: ## document read, in part:
035353,000025: ##
035354,000026: ## Assemble revision 249 of AGC program Colossus by NASA
035355,000027: ## 2021111-041. October 28, 1968.
035356,000028: ##
035357,000029: ## This AGC program shall also be referred to as
035358,000030: ## Colossus 1A
035359,000031: ##
035360,000032: ## Prepared by
035361,000033: ## Massachusetts Institute of Technology
035362,000034: ## 75 Cambridge Parkway
035363,000035: ## Cambridge, Massachusetts
035364,000036: ## under NASA contract NAS 9-4065.
035365,000037: ##
035366,000038: ## Refer directly to the online document mentioned above for further information.
035367,000039: ## Please report any errors (relative to the scanned pages) to info@sandroid.org.
035368,000040: ##
035369,000041: ## In some cases, where the source code for Luminary 131 overlaps that of
035370,000042: ## Colossus 249, this code is instead copied from the corresponding Luminary 131
035371,000043: ## source file, and then is proofed to incorporate any changes.
035372,000044:
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Page 791 |
035374,000046: # VARIABLE DESCRIPTION MAXIMUM VALUE * COMPUTER NAME
035375,000047: # -------- ----------- ------- ----- -------- ----
035376,000048: # -
035377,000049: # URT0 INITIAL TARGET VECTOR 2 (UNIT VECTOR) = RTINIT
035378,000050: # -
035379,000051: # UZ UNIT VECTOR NORTH 1 = UNITW
035380,000052: # -
035381,000053: # V VELOCITY VECTOR 2 VSAT = VEL
035382,000054: # -
035383,000055: # R POSITION VECTOR 2 EXP 29 METERS = RN
035384,000056: # -
035385,000057: # VI INERTIAL VELOCITY 128 M/CENTISEC = VN
035386,000058: # -
035387,000059: # RTE VECTOR EAST AT INITIAL TARGET 2 = RTEAST
035388,000060: # -
035389,000061: # UTR NORMAL TO RTE AND UZ 2 = RTNORM
035390,000062: # -
035391,000063: # URT TARGET VECTOR 2 = RT
035392,000064: # -
035393,000065: # UNI UNIT NORMAL TO TRAJECTORY PLANE 2
035394,000066: # -
035395,000067: # DELV INTEGRATED ACCEL. FROM PIPAS 5.85 16384 CM/S
035396,000068: # -
035397,000069: # G GRAVITY VECTOR 128 M/CENTISEC = GDT/2
035398,000070:
035399,000071: # A0 INITIAL DRAG FOR UPCONTRL 805 FPSS FPSS=FT/SEC/SEC
035400,000072:
035401,000073: # AHOOKDV TERM IN GAMMAL CALC. = AHOOK DVL 16
035402,000074:
035403,000075: # A1 DRAG VALUE IN FACTOR CALCULATION 805 FPSS
035404,000076:
035405,000077: # ALP CONST FOR UPCONTRL 1
035406,000078:
035407,000079: # ASKEP KEPLER RANGE 21600 NM NM = NAUTICAL MILE
035408,000080:
035409,000081: # ASP1 FINAL PHASE RANGE 21600 NM
035410,000082:
035411,000083: # ASPUP UP-RANGE 21600 NM
035412,000084:
035413,000085: # ASP3 GAMMA CORRECTION 21600 NM
035414,000086:
035415,000087: # ASPDWN RANGE DOWN TO PULL-UP 21600 NM
035416,000088:
035417,000089: # ASP PREDICTED RANGE 21600 NM NOT STORED
035418,000090:
035419,000091: # COSG COSINE(GAMMAL) 2 = COSG/2
035420,000092:
035421,000093: # C/D0 RECIPROCAL DRAG, -4/D0 B-8 64/FPSS
035422,000094:
035423,000095: # D TOTAL ACCELERATION 805 FPSS
035424,000096:
035425,000097: # D0 CONTROLLED CONSTANT D 805 FPSS
035426,000098:
035427,000099: # DHOOK TERM IN GAMMAL COMPUTATION 805 FPSS
035428,000100:
035429,000101: # DIFF THETNM-ASP (RANGE DIFFERENCE) 21600 NM
035430,000102:
035431,000103: # DIFFOLD PREVIOUS VALUE OF DIFF 21600 NM
035432,000104:
035433,000105: # DLEWD CHANGE IN LEWD 1
035434,000106:
035435,000107: # DR REFERENCE DRAG FOR DOWNCONTROL 805 FPSS NOT STORED
035436,000108:
035437,000109: # DREFR REFERENCE DRAG 805 FPSS NOT STORED
035438,000110:
035439,000111: # DVL VS1-VL 2 VSAT
035440,000112:
035441,000113: # E ECCENTRICITY 4 NOT STORED
035442,000114:
035443,000115: # F1 DRANGE/D DRAG (FINAL PHASE) 2700/805 = FX +5
035444,000116:
035445,000117: # F2 DRANGE/D RDOT (FINAL PHASE) 2700/2VS NM/FPS = FX +4
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Page 792 |
035447,000119:
035448,000120: # F3 DRANGE/D (L/D) 2700 NM = FX
035449,000121:
035450,000122: # FACT1 CONST FOR UPCONTRL 805 FPSS
035451,000123:
035452,000124: # FACT2 CONST FOR UPCONTRL 1/805 FPSS
035453,000125:
035454,000126: # FACTOR USED IN UPCONTRL 1 * MAXIMUM VALUE DENOTES UNSCALED
035455,000127: #
035456,000128: # GAMMAL FLIGHT PATH ANGLE AT VL 1 RADIAN VARIABLE VALUE WHEN SCALED
035457,000129:
035458,000130: # GAMMAL1 SIMPLE FORM OF GAMMAL 1 RADIAN VARIABLE HAS MAXIMUM VALUE OF ONE.
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Page 793 |
035460,000132: # VARIABLE DESCRIPTION MAXIMUM VALUE COMPUTER NAME
035461,000133: # -------- ----------- ------- ----- -------- ----
035462,000134:
035463,000135: # HEADSUP INDICATOR FOR INITIAL ROLL 1
035464,000136:
035465,000137: # KA DRAG TO LIFT UP IF DOWN 805 FPSS = KAT
035466,000138:
035467,000139: # KLAT LATERAL SWITCH GAIN 1 (NOM = .0125)
035468,000140:
035469,000141: # K2ROLL INDICATOR FOR ROLL SWITCH
035470,000142:
035471,000143: # LAD MAX L/D (MIN ACTUAL VEHICLE L/D) 1
035472,000144:
035473,000145: # LADPAD NOMINAL VEHICLE L/D, SP PAD LOAD 1 (NOM = 0.3)
035474,000146:
035475,000147: # LATANG LATERAL RANGE 4 RADIANS
035476,000148:
035477,000149: # LEQ EXCESS C.F. OVER GRAV=(VSQ-1)GS 128.8 FPSS
035478,000150:
035479,000151: # LEWD UPCONTROL REFERENCE L/D 1
035480,000152:
035481,000153: # LOD FINAL PHASE L/D 1 (NOM = 0.18)
035482,000154:
035483,000155: # LODPAD FINAL PHASE L/D, SP PAD LOAD 1
035484,000156:
035485,000157: # L/D DESIRED LIFT TO DRAG RATIO 1
035486,000158: # (VERTICAL PLANE)
035487,000159: #
035488,000160: # L/D1 TEMP STORAGE FOR L/D IN LATERAL 1
035489,000161:
035490,000162: # L/DCMINR LAD COS(15DEG) 1 (NOM = 0.2895)
035491,000163:
035492,000164: # PREDANGL PREDICTED RANGE (FINAL PHASE) 2700 NM = PREDANG
035493,000165:
035494,000166: # Q2 FINAL PHASE RANGE -23500 Q3 21600 NM
035495,000167: # Q2 = FCN(LAD)
035496,000168:
035497,000169: # Q7 MINIMUM DRAG FOR UPCONTROL 805FPSS
035498,000170:
035499,000171: # RDOT ALTITUDE RATE 2 VSAT
035500,000172:
035501,000173: # RDOTREF REFERENCE RDOT FOR UPCONTROL 2 VSAT
035502,000174:
035503,000175: # RDTR REFERENCE RDOT FOR DOWNCONT 2 VSAT NOT SAVED
035504,000176:
035505,000177: # ROLLC ROLL COMMAND 1 REVOLUTION
035506,000178:
035507,000179: # RTOGO RANGE TO GO (FINAL PHASE) 2700 NM = FX +2
035508,000180:
035509,000181: # SL SINE OF LATITUDE 1 NOT SAVED
035510,000182:
035511,000183: # T TIME B 28 CENTISEC = TIME2,TIME1
035512,000184:
035513,000185: # THETA DESIRED RANGE (RADIANS) 2 PI RADIANS = THETAH
035514,000186:
035515,000187: # THETNM DESIRED RANGE (NM) 21600 NM NON EXISTENT
035516,000188:
035517,000189: # V VELOCITY MAGNITUDE 2 VSAT
035518,000190: #
035519,000191: # V1 INITIAL VELOCITY FOR UPCONTROL 2 VSAT
035520,000192:
035521,000193: # VL EXIT VELOCITY FOR UPCONTROL 2 VSAT
035522,000194:
035523,000195: # VREF REFERENCE VELOCITY FOR UPCONTROL 2 VSAT
035524,000196:
035525,000197: # VS1 VSAT OR V1, WHICHEVER IS SMALLER 2 VSAT
035526,000198: # 2 2
035527,000199: # VBARS VL /VSAT 4
035528,000200: # 2 2
035529,000201: # VSQ NORMALISED VEL. SQUARED = V /VSAT 4 = VSQUARE
035530,000202:
035531,000203: # WT EARTH RATE TIMES TIME 1 REVOLUTION NOT SAVED
035532,000204: # = WIE (DTEAROT)
035533,000205: # X INTERMEDIATE VARIABLE IN G-LIMITER 2 VSAT NOT SAVED
035534,000206:
035535,000207: # Y LATERAL MISS LIMIT 4 RADIANS NOT SAVED
035536,000208:
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Page 794 |
035538,000210: # EXTRA COMPUTER ERASABLE LOCATIONS NOT SHOWN ON FLOW CHARTS
035539,000211: # -----------------------------------------------------------
035540,000212:
035541,000213: # VARIABLE DESCRIPTION MAXIMUM VALUE
035542,000214: # -------- ----------- ------- -----
035543,000215:
035544,000216: # GOTOADDR ADDRESS SELECTED BY SEQUENCER
035545,000217:
035546,000218: # XPIPBUF BUFFER TO STORE X PIPA COUNTS
035547,000219:
035548,000220: # YPIPBUF BUFFER TO STORE Y PIPA COUNTS
035549,000221:
035550,000222: # ZPIPBUF BUFFER TO STORE Z PIPA COUNTS
035551,000223:
035552,000224: # PIPCTR COUNTS PASSES THRU PIPA READ ROUTINE
035553,000225:
035554,000226: # JJ INDEX IN FINAL PHASE TABLE LOOK-UP
035555,000227:
035556,000228: # MM INDEX IN FINAL PHASE TABLE LOOK-UP
035557,000229:
035558,000230: # GRAD INTERPOLATION FACTOR IN FINAL PHASE
035559,000231:
035560,000232: # FX DRANGE/D L/D = F3 2700 NM
035561,000233:
035562,000234: # FX +1 AREF 805 FPSS
035563,000235:
035564,000236: # FX +2 RTOGO 2700 NM
035565,000237:
035566,000238: # FX +3 RDOTREF VSAT/4
035567,000239:
035568,000240: # FX +4 DRANGE/D RDOT = F2 21600/2VS NM/FPS
035569,000241:
035570,000242: # FX +5 DRANGE/D DRAG = F1 2700/805 NM/FPSS
035571,000243:
035572,000244: # TEM1B TEMPORARY LOCATION
035573,000245:
035574,000246: # TIME/RTO TIME OF INITIAL TARGET RTINIT B 28 CENTISEC
035575,000247:
035576,000248: # DTEAROT EST TIME BETWEEN RTINIT AND RT B 28 CENTISEC
035577,000249: # -
035578,000250: # UNITV UNIT V VECTOR 2
035579,000251: # -
035580,000252: # UNITR UNIT R VECTOR 2
035581,000253: # -
035582,000254: # -VREL NEGATIVE VELOCITY REL TO ATMOSP 2 VSAT
035583,000255:
035584,000256: # COMPUTER SWITCHES INITIAL STATE CM/FLAGS = STATE +6
035585,000257: # -------- -------- ------------- -------------------
035586,000258:
035587,000259: # ENTRYDSP DO ENTRY DISPLAY, IF SET NON-BRANCH (1) 92D, BIT 13
035588,000260: # GONEPAST INDICATES OVERSHOOT OF TARGET NON-BRANCH (0) 95D, BIT 10
035589,000261: # RELVELSW RELATIVE VELOCITY SWITCH NON-BRANCH (0) 96D, BIT 9
035590,000262: # EGSW FINAL PHASE SWITCH NON-BRANCH (0) 97D, BIT 8
035591,000263: # FIRSTPAS INITIAL PASS THRU HUNTEST NON-BRANCH (0) 98D, BIT 7
035592,000264: # HIND INDICATES ITERATION IN HUNTEST NON-BRANCH (0) 99D, BIT 6
035593,000265: # INRLSW INDICATES INIT ROLL ATTITUDE SET NON-BRANCH (0) 100D, BIT 5
035594,000266: # LATSW INHIBIT DOWNLIFT SWITCH IF NOT SET BRANCH (1) 101D, BIT 4
035595,000267: # .05GSW INDICATES DRAG EXCEEDS .05 GS BRANCH (0) 102D, BIT 3
035596,000268:
035597,000269: # GONEBY INDICATES GONE PAST TARGET (SET) SELF-INITIALZNG 112D, BIT 8
035598,000270:
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Page 795 |
035600,000272: # CONSTANTS AND GAINS VALUE
035601,000273: # ------------------- -----
035602,000274:
035603,000275: # C1 FACTOR IN ALP COMPUTATION 1.25
035604,000276: # C16 CONSTD GAIN ON DRAG .01
035605,000277: # C17 CONSTD GAIN ON RDOT .001
035606,000278: # C18 BIAS VEL. FOR FINAL PHASE START 500 FPS
035607,000279: # C20 MAX DRAG FOR DOWN-LIFT 175 FPSS
035608,000280: # CHOOK FACTOR IN AHOOK COMPUTATION .25
035609,000281: # CH1 FACTOR IN GAMMAL COMPUTATION 1.0
035610,000282: # COS15 COS( 15 DEG ) .965
035611,000283: # DLEWD0 INITIAL VARIATION IN LEWD -.05
035612,000284: # D2 DRAG TO CHANGE LEWD 175 FPSS
035613,000285: # DT COMPUTATION CYCLE TIME INTERVAL 2 SEC.
035614,000286: # GMAX MAXIMUM ACCELERATION 257.6 FPSS (8 G-S)
035615,000287: # KA1 FACTOR IN KA CALC 1.3 GS
035616,000288: # KA2 FACTOR IN KA CALC .2 GS
035617,000289: # KA3 FACTOR IN D0 CALC 90 FPSS
035618,000290: # KA4 FACTOR IN D0 CALC 40 FPSS
035619,000291: # KB1 OPTIMIZED UPCONTROL GAIN 3.4
035620,000292: # KB2 OPTIMIZED UPCONTROL GAIN .0034
035621,000293: # KDMIN INCREMENT ON Q7 TO DETECT END OF KEPLER PHASE .5 FPSS
035622,000294: # KTETA TIME OF FLIGHT CONSTANT 1000
035623,000295: # KLAT1 FACTOR IN KLAT CALC 1/24
035624,000296: # K44 GAIN USED IN INITIAL ROLL SECTION 19749550 FPS
035625,000297: # LATBIAS LATERAL SWITCH BIAS TERM .41252961 NM
035626,000298: # LEWD1 NOMINAL UPCONTROL L/D .15
035627,000299: # POINT1 FACTOR TO REDUCE UPCONTROL GAIN .1
035628,000300: # Q2 FINAL PHASE RANGE - 23500 Q3 -1002 NM
035629,000301: # Q3 FINAL PHASE DRANGE/D V .07 NM/FPS
035630,000302: # Q5 FINAL PHASE DRANGE/D GAMMA 7050 NM/RAD
035631,000303: # Q6 FINAL PHASE INITIAL FLIGHT PATH ANGLE .0349 RAD
035632,000304: # Q7F MIN DRAG FOR UPCONTROL 6 FPSS
035633,000305: # Q7MIN MIN VALUE FOR Q7 IN FACTOR CALCULATION 40 FPSS
035634,000306: # Q19 FACTOR IN GAMMAL1 CALCULATION .5
035635,000307: # Q21 FACTOR IN Q2 CALCULATION. 1000 NM
035636,000308: # Q22 FACTOR IN Q2 CALCULATION. -1302 NM
035637,000309: # VFINAL1 VELOCITY TO START FINAL PHASE ON INITIAL ENTRY 27000 FPS
035638,000310: # VFINAL FACTOR IN INITIAL UP-DOWN CALC 26600 FPS
035639,000311: # VLMIN MINIMUM VL 18000 FPS
035640,000312: # VMIN VELOCITY TO SWITCH TO RELATIVE VEL VSAT/2
035641,000313: # VRCONTRL RDOT TO START INTO HUNTEST 700 FPS
035642,000314: # VRCONT=COMPUTER NAME
035643,000315: # 25NM TOLERANCE TO STOP RANGE ITERATION 25 NM
035644,000316: # VQUIT VELOCITY TO STOP STEERING 1000 FPS
035645,000317:
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Page 796 |
035647,000319: # CONVERSION FACTORS AND SCALING CONSTANTS
035648,000320: # ---------- ------- --- ------- ---------
035649,000321:
035650,000322: # ATK ANGLE IN RAD TO NM 3437.7468 NM/RAD
035651,000323: # GS NOMINAL G VALUE FOR SCALING 32.2 FPSS
035652,000324: # HS ATMOSPHERE SCALE HEIGHT 28500 FT
035653,000325: # J GRAVITY HARMONIC COEFFICIENT .00162346
035654,000326: # KWE EQUATORIAL EARTH RATE 1546.70168 FPS
035655,000327: # MUE EARTH GRAVITATIONAL CONSTANT 3.986032233 E14 CUBIC M/ SEC SEC
035656,000328: # RE EARTH RADIUS 21202900 FT
035657,000329: # REQ EARTH EQUATORIAL RADIUS 20925738.2 FT
035658,000330: # VSAT SATELLITE VELOCITY AT RE 25766.1973 FPS
035659,000331: # WIE EARTH RATE .0000729211505 RAD/SEC
035660,000332:
035661,000333: # (END GSOP AS-278, VOL 1, FIG. 5.6-3 CONSTANTS, GAINS, ETC.)
035662,000334:
035663,000335: # DISPLAY QUANTITIES
035664,000336: # ------------------
035665,000337:
035666,000338: # (SEE SECTION 4 OF THE GSOP FOR SIGN CONVENTIONS.)
035667,000339:
035668,000340: # VARIABLE DESCRIPTION MAXIMUM VALUE
035669,000341: # -------- ----------- ------- -----
035670,000342:
035671,000343: # QMAX PREDICTED MAXIMUM ENTRY ACCEL 163.84 GS N 60
035672,000344: # VPRED PREDICTED VELOCITY AT ALTITUDE 128 M/CENTISEC N 60
035673,000345: # 400K FT ABOVE FISCHER RADIUS.
035674,000346: # GAMMAEI PREDICTED GAMMA AT ALTITUDE 1 REVOLUTION N 60
035675,000347: # 400K FT ABOVE FISCHER RADIUS.
035676,000348: # D DRAG ACCELERATION 805 FPSS N 64
035677,000349: # VMAGI INERTIAL VELOCITY MAGNITUDE 128 M/CENTISEC N 64, N 68
035678,000350: # THETAH DESIRED RANGE ANGLE NM 1 REVOLUTION N 64, N 67
035679,000351: # LAT PRESENT LATITUDE 1 REVOLUTION N 67
035680,000352: # LONG PRESENT LONGITUDE 1 REVOLUTION N 67
035681,000353: # RTOGO RANGE ANGLE TO SPLASH FROM 1 REVOLUTION N 63
035682,000354: # EMSALT FT ABOVE FISCHER RADIUS. (IN NM)
035683,000355: # VIO PREDICTED VELOCITY AT ALTITUDE 128 M/CENTISEC N 63
035684,000356: # EMSALT FT ABOVE FISCHER RADIUS.
035685,000357: # TTE TIME OF FREE FALL TO ALT B 28 CENTISEC N 63
035686,000358: # EMSALT FT ABOVE FISCHER RADIUS.
035687,000359: # ROLLC ROLL COMMAND 1 REVOLUTION N 66, N 68, N 69
035688,000360: # LATANG CROSS-RANGE ERROR (XRNGERR) 4 RADIANS N 66
035689,000361: # DNRNGERR DOWN RANGE ERROR 1 REVOLUTION N 66
035690,000362: # (PREDANG - THETAH IN NM)
035691,000363: # HDOT ALTITUDE RATE 128 M/CENTISEC N 68
035692,000364: # Q7 MINIMUM DRAG FOR UPCONTROL 805 FPSS N 69
035693,000365: # VL EXIT VELOCITY FOR UP-CONTROL 2 VSAT N 69
035694,000366:
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Page 797 |
035696,000368: # BODY ATTITUDE QUANTITIES (CM/POSE)
035697,000369: # -----------------------------------
035698,000370:
035699,000371: # VARIABLE DESCRIPTION MAXIMUM VALUE
035700,000372: # -------- ----------- ------- -----
035701,000373: # -
035702,000374: # -VREL NEGATIVE VELOCITY REL TO ATMOS. 2 VSAT
035703,000375: # -
035704,000376: # OLDUYA USED FOR UYA BELOW 1000 FPS 2
035705,000377: # -
035706,000378: # UXA/2 UNIT VECTOR TRIAD 2
035707,000379: # -
035708,000380: # UYA/2 BASED ON 2
035709,000381: # -
035710,000382: # UZA/2 THE TRAJECTORY. 2
035711,000383: # -
035712,000384: # UBX/2 UNIT VECTOR 2
035713,000385: # -
035714,000386: # UBY/2 BODY TRIAD 2
035715,000387: # -
035716,000388: # UBZ/2 FOR CM. 2
035717,000389:
End of include-file ENTRY_LEXICON.agc. Parent file is MAIN.agc