Source Code
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These source-code files were transcribed from scans made from Don Eyles's personal
copy of BURST120 (SUNBURST 120). They were scanned at archive.org's Boston
facility, and the scanning was sponsored by Mike Stewart. The code was transcribed
from these scans by a team of volunteers who are referenced in the program
comments. Comments from the original source code are in ALL-CAPS, whereas
comments added later in transcription are in Mixed-Case. In some cases, where
similar code blocks exist in previously-transcribed AGC programs (primarily
Luminary 99, from Apollo 11) those code blocks were used as a starting point and
then corrected to agree with the BURST120 scans. The full scans are available
at the Virtual AGC
project's collection at archive.org, while more-convenient reduced-size (but reduced-quality)
images are available at
the main Virtual AGC website. Report any errors noted by creating an
issue report at the Virtual AGC
project's GitHub repository. Notations on the program listing read, in part:YUL SYSTEM FOR AGC: REVISION 0 OF PROGRAM BURST120 BY NASA 2021106-031 DEC 7, 1967 THIS LISTING IS A COPY OF A VERSION OF THE PROGRAM INTENDED FOR USE IN THE ON-BOARD PRIMARY GUIDANCE COMPUTER IN THE UNMANNED FLIGHT OF APOLLO LUNAR MODULE 1 --- THE AS206 MISSION.Note that the date is the date of the printout, not the date of the program revision. |
036059,000002: ## Copyright: Public domain.
036060,000003: ## Filename: MASS_CALCULATOR.agc
036061,000004: ## Purpose: A module for revision 0 of BURST120 (Sunburst). It
036062,000005: ## is part of the source code for the Lunar Module's
036063,000006: ## (LM) Apollo Guidance Computer (AGC) for Apollo 5.
036064,000007: ## Assembler: yaYUL
036065,000008: ## Contact: Ron Burkey <info@sandroid.org>.
036066,000009: ## Website: www.ibiblio.org/apollo/index.html
036067,000010: ## Mod history: 2016-09-30 RSB Created draft version.
036068,000011: ## 2016-10-30 MAS Transcribed.
036069,000012: ## 2016-12-06 RSB Comment-proofing via octopus/ProoferComments;
036070,000013: ## changes were made.
036071,000014:
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036073,000016: 30,3206 BANK 30
036074,000017: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
036075,000018:
036076,000019: # THE MASS UPDATE ROUTINE EXTENDS FROM APPROXIMATELY HERE TO THE NEXT
036077,000020: # ROW OF ASTERISKS. COMPUTATIONS ARE AS FOLLOWS:-
036078,000021: # (1) /AF/ = MAGNITUDE DV/DT, SCALED IN UNITS OF 2(-5) M/CS/CS.
036079,000022: # (2) PREFORCE = /AF/ MASS, APPROXIMATE PRESENT THRUST, SCALED AT
036080,000023: # SOME 3.3 POUNDS PER BIT; PREFORCE LATER BECOMES PREFORCE/2FMAX.
036081,000024: # (3) NOMINAL EXHAUST VELOCITY, VEXNOM = VEXSTEP + (PREFORCE-FSTEP)
036082,000025: # SLOPE, WHERE VEXSTEP, FSTEP, AND SLOPE ARE SELECTED FROM THE
036083,000026: # 'VEXTABLE' BY THE ROUTINE BEGINNING AT VEXFINDD; THE FSTEPS
036084,000027: # AND VXSTEPS DEFINE CERTAIN DISCRETE POINTS ON THE CURVE OF
036085,000028: # EXHAUST VELOCITY VERSUS THRUST; THE ASSOCIATED SLOPE IS ALWAYS
036086,000029: # THAT FOR THE SEGMENT JUST PRECEEDING THOSE POINTS. (UNITS
036087,000030: # FOR VEXNOM, AS FOR NEGVEX, ARE 2(6) M/CS.)
036088,000031: # (4) AREARATE, A MODERATELY ABSTRUSE (NOT TO SAY ABSURD) FUNCTION
036089,000032: # OF DELAREA (EROSION) AND PREFORCE. (THE AREA IN QUESTION IS
036090,000033: # THAT OF THE THROAT OF THE ENGINE.)
036091,000034: # (5) DELAREA = DELAREA + AREARATE DELTAT, SCALED IN UNITS OF 2(7) %
036092,000035: # (6) NEGVEX = -(VEXNOM - CVEX5 DELAREA).
036093,000036: # (7) MASS = MASS + (/DELV//NEGVEX) MASS, SCALED IN UNITS OF 2(15)
036094,000037: # KILOGRAMS.
036095,000038:
036096,000039: # THE FOLLOWING INITIALIZATIONS MUST BE MADE BEFORE LAUNCH:
036097,000040: # C(MASS) = 0, C(LEMMASS1) = SCALED MASS OF LEM CUM DPS, C(LEMMASS2) =
036098,000041: # SCALED MASS OF LEM WITHOUT DPS. UPON LEM-SIVB SEPARATION MASS MUST
036099,000042: # BE REINITIALIZED USING LEMMASS1 AND DELAREA MUST BE SET TO DP ZERO.
036100,000043: # LATER, WHEN THE DPS PARTS COMPANY, MASS MUST BE INITIALIZED STILL
036101,000044: # AGAIN USING LEMMASS2.
036102,000045:
036103,000046: # THE FOLLOWING IS AN INELEGANT SUPERFLUITY:- INPUTS: MASS, DELAREA,
036104,000047: # DELV, DELTAT, EMANATIONS FROM THE VEXTABLE, A TABLESPOON OF SALT AND
036105,000048: # SEVEN BYZANTINE DODO EGGS. OUTPUTS: /AF/ AND MASS. DEBRIS: PREFORCE,
036106,000049: # NEGVEX, AND AREARATE (TO LEARN MORE ABOUT THESE GEMS, SEE ABOVE).
036107,000050: # SUBROUTINES CALLED: MASSMULT (A PART OF THROTTLE CONTROL) AND THE
036108,000051: # INTERPRETER. ERASABLES: BANK 5 AT PRESENT. EYLES WROTE THIS STUFF;
036109,000052: # HIS LAST MODIFICATION THEREOF (NUMBER N+2) WENT INTO AGC REVISION 20.
036110,000053:
036111,000054: 30,3206 43145 MASSMON DLOAD BOFF
036112,000055: 30,3207 01321 MASS
036113,000056: 30,3210 00753 SIVBGONE
036114,000057: 30,3211 61373 NOMASS
036115,000058: 30,3212 74375 VLOAD VXSC
036116,000059: 30,3213 00404 DELV # DV = DELV*KPIP SCALED AT 2(+4) M/CS
036117,000060: 30,3214 21163 KPIP
036118,000061: 30,3215 51406 PUSH ABVAL # DV IN PDL
036119,000062: 30,3216 03624 STORE ABDVCONV
036120,000063: 30,3217 56206 PUSH DDV
036121,000064: 30,3220 21400 2SEC(9)
036122,000065: 30,3221 01325 STORE /AF/ # /AF/ = MAGNITUDE DV/DT
036123,000066:
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036125,000068: 30,3222 77776 EXIT
036126,000069:
036127,000070: 30,3223 33444 CA ETHROTL
036128,000071: 30,3224 54003 TS EBANK # JUST TO INSURE HAVING THE PROPER EBANK
036129,000072: 30,3225 E5,1565 EBANK= ETHROT
036130,000073:
036131,000074: 30,3225 00006 EXTEND
036132,000075: 30,3226 31325 DCA /AF/
036133,000076: 30,3227 03445 TC MASSMULT # WHICH PRODUCES DP FORCE IN A AND L
036134,000077: 30,3230 53546 DXCH PREFORCE
036135,000078:
036136,000079: 30,3231 41545 CHOICE1 CS PREFORCE # TEST PREFORCE TO SEE IF
036137,000080: 30,3232 63401 AD LOWFCRIT # EITHER BIG ENGINE IS ON
036138,000081: 30,3233 00006 EXTEND
036139,000082: 30,3234 63241 BZMF CHOICE2 # BRANCH IF PREFORCE > LOWFCRIT = 720 LBS.
036140,000083:
036141,000084: 30,3235 00006 VEXFINDR EXTEND # OTHERWISE, USE RCSVEX
036142,000085: 30,3236 43404 DCS RCSVEX
036143,000086: 30,3237 53556 DXCH NEGVEX
036144,000087: 30,3240 13252 TCF MININIT
036145,000088: 30,3241 00006 CHOICE2 EXTEND
036146,000089: 30,3242 00030 READ 30
036147,000090: 30,3243 40000 COM
036148,000091: 30,3244 77762 MASK BIT2
036149,000092: 30,3245 00006 EXTEND
036150,000093: 30,3246 13256 BZF VEXFINDD
036151,000094: 30,3247 00006 VEXFINDA EXTEND # OTHERWISE, USE APSVEX
036152,000095: 30,3250 43406 DCS APSVEX
036153,000096: 30,3251 53556 DXCH NEGVEX
036154,000097: 30,3252 00006 MININIT EXTEND
036155,000098: 30,3253 33415 DCA MINMASSA
036156,000099: 30,3254 53564 DXCH MINIMASS
036157,000100: 30,3255 13351 TCF ENDVEX
036158,000101:
036159,000102: 30,3256 00006 VEXFINDD EXTEND
036160,000103: 30,3257 33417 DCA MINMASSD
036161,000104: 30,3260 53564 DXCH MINIMASS
036162,000105:
036163,000106: 30,3261 37767 CA ZERO
036164,000107: 30,3262 55544 TS VEXDEX
036165,000108: 30,3263 37761 VEXLOOP CA FOUR
036166,000109: 30,3264 27544 ADS VEXDEX # INCREMENTING VEXDEX BY FOUR
036167,000110: 30,3265 41545 CS PREFORCE
036168,000111: 30,3266 51544 INDEX VEXDEX
036169,000112: 30,3267 63414 AD FSTEP # FSTEP - PREFORCE IN A AND L
036170,000113: 30,3270 00006 EXTEND
036171,000114: 30,3271 63263 BZMF VEXLOOP # BRANCH IF PREFORCE > OR = FSTEP. EMERGE
036172,000115: # FROM LOOP WITH INDEX PROPERLY SET AS
036173,000116: # SOON AS FSTEP > PREFORCE.
036174,000117: 30,3272 40000 COM # PREFORCE-FSTEP (ALWAYS MINUS) IN A AND L
036175,000118:
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036177,000120: 30,3273 00006 EXTEND
036178,000121: 30,3274 51544 INDEX VEXDEX
036179,000122: 30,3275 73415 MP SLOPE
036180,000123: 30,3276 53550 DXCH VEXNOM
036181,000124: 30,3277 00006 EXTEND
036182,000125: 30,3300 51544 INDEX VEXDEX
036183,000126: 30,3301 33417 DCA VEXSTEP
036184,000127: 30,3302 21550 DAS VEXNOM # VEXNOM = VEXSTEP + (PREFORCE-FSTEP)SLOPE
036185,000128:
036186,000129: 30,3303 43700 CS -FMAX
036187,000130: 30,3304 60000 DOUBLE
036188,000131: 30,3305 56002 XCH Q
036189,000132: 30,3306 00006 EXTEND
036190,000133: 30,3307 31546 DCA PREFORCE
036191,000134: 30,3310 00006 EXTEND
036192,000135: 30,3311 10002 DV Q
036193,000136: 30,3312 55545 TS PREFORCE # PREFORCE = PREFORCE/2FMAX
036194,000137:
036195,000138: 30,3313 33412 CA CVEX4
036196,000139: 30,3314 00006 EXTEND
036197,000140: 30,3315 71551 MP DELAREA
036198,000141: 30,3316 63411 AD CVEX3
036199,000142: 30,3317 00006 EXTEND
036200,000143: 30,3320 71545 MP PREFORCE
036201,000144: 30,3321 00006 EXTEND # MUMBO
036202,000145: 30,3322 71545 MP PREFORCE # JUMBO
036203,000146: 30,3323 53554 DXCH AREARATE
036204,000147: 30,3324 33410 CA CVEX2
036205,000148: 30,3325 00006 EXTEND
036206,000149: 30,3326 71551 MP DELAREA
036207,000150: 30,3327 63407 AD CVEX1
036208,000151: 30,3330 00006 EXTEND
036209,000152: 30,3331 71545 MP PREFORCE
036210,000153: 30,3332 21554 DAS AREARATE # NOW SCALED IN UNITS OF 2(-2) PERCENT/CS
036211,000154: 30,3333 31553 CA AREARATE
036212,000155: 30,3334 00006 EXTEND
036213,000156: 30,3335 73377 MP 2SEC(9)
036214,000157: 30,3336 53560 DXCH DAREATMP
036215,000158: 30,3337 00006 EXTEND
036216,000159: 30,3340 31552 DCA DELAREA
036217,000160: 30,3341 21560 DAS DAREATMP # DAREATMP NOW CONTAINS NEW DELAREA
036218,000161: 30,3342 31557 CA DAREATMP
036219,000162: 30,3343 00006 EXTEND
036220,000163: 30,3344 73413 MP CVEX5
036221,000164: 30,3345 53556 DXCH NEGVEX # RESULT IS SCALED IN UNITS OF 2(6) M/CS
036222,000165: 30,3346 00006 EXTEND
036223,000166: 30,3347 41550 DCS VEXNOM
036224,000167: 30,3350 21556 DAS NEGVEX # NEGVEX NOW HOLDS THE GENUINE ARTICLE
036225,000168:
036226,000169: 30,3351 37767 ENDVEX CA ZERO # PRECAUTIONARY
036227,000170:
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036229,000172: 30,3352 54153 TS MODE
036230,000173: 30,3353 54111 TS OVFIND
036231,000174:
036232,000175: 30,3354 06112 TC INTPRET
036233,000176: 30,3355 60545 DLOAD SR2 # RESCALING /DELV/ TO 2(6) M/CS
036234,000177: 30,3356 41271 DDV DMP
036235,000178: 30,3357 02556 NEGVEX
036236,000179: 30,3360 01321 MASS
036237,000180: 30,3361 77615 DAD
036238,000181: 30,3362 01321 MASS
036239,000182: 30,3363 02562 STORE MASSTEMP
036240,000183: 30,3364 51025 DSU BPL # RETURN NOW IF MASS > MINIMASS
036241,000184: 30,3365 02564 MINIMASS
036242,000185: 30,3366 00052 QPRET
036243,000186: 30,3367 77745 DLOAD # OTHERWISE SET MASS = MINIMASS
036244,000187: 30,3370 02564 MINIMASS
036245,000188: 30,3371 02562 STORE MASSTEMP
036246,000189: 30,3372 77616 RVQ
036247,000190:
036248,000191: 30,3373 16562 NOMASS STODL MASSTEMP
036249,000192: 30,3374 26643 DP0
036250,000193: 30,3375 02560 STORE DAREATMP # DELAREA INITIALIZED UNTIL SIVB SEPARATES
036251,000194: 30,3376 77616 RVQ
036252,000195:
036253,000196: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
036254,000197: # * * * * * * * * * * * * * * * * * * * *
036255,000198:
036256,000199: # CONSTANTS FOR VEXFIND1
036257,000200:
036258,000201: 30,3377 14400 00000 2SEC(9) 2DEC 200 B-9 # CONSTANT GUIDANCE PERIOD, SUP70S5DLY
036259,000202:
036260,000203:
036261,000204:
036262,000205: 30,3401 00411 LOWFCRIT OCT 411 # ABOUT 720 POUNDS, SCALED
036263,000206: 30,3402 05423 MASSCRIT DEC .173031964 # MASS OF LEM WITH DPS > MASSCRIT > MASS
036264,000207: # OF LEM WITHOUT DPS
036265,000208:
036266,000209: 30,3403 15165 30244 RCSVEX 2DEC .4134375 # EXHAUST VELOCITY FOR RCS JETS
036267,000210:
036268,000211: 30,3405 17114 33562 APSVEX 2DEC .473441550 # EXHAUST VELOCITY FOR ASCENT ENGINE
036269,000212:
036270,000213: 30,3407 00316 CVEX1 DEC +.012558840
036271,000214: 30,3410 76221 CVEX2 DEC -.053575066
036272,000215: 30,3411 77312 CVEX3 DEC -.018875329
036273,000216: 30,3412 02447 CVEX4 DEC +.080517427
036274,000217: 30,3413 01503 CVEX5 DEC +.05099460
036275,000218:
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036277,000220: 30,3414 02035 07567 MINMASSA 2DEC 2106.4833 B-15 # MASS OF APS EMPTY
036278,000221:
036279,000222: 30,3416 06062 20000 MINMASSD 2DEC 6245 B-15 # DESCENT WITH NO DPS FUEL AND 405 RCS
036280,000223:
036281,000224:
036282,000225: # ADDRESSES FOR ACCESSING VEXTABLE
036283,000226:
036284,000227: 30,3420 30,3414 FSTEP = FSTEP1 -4
036285,000228: 30,3420 30,3415 SLOPE = SLOPE1 -4
036286,000229: 30,3420 30,3416 VEXSTEP = VXSTEP1 -4
036287,000230:
036288,000231: # THE VEXTABLE
036289,000232:
036290,000233: 30,3420 01713 FSTEP1 DEC +.0592346907 # 25%
036291,000234: 30,3421 11736 SLOPE1 DEC +.3104172317
036292,000235: 30,3422 16445 06644 VXSTEP1 2DEC +.4553963093 # ABOUT 2914.53 M/S
036293,000236:
036294,000237:
036295,000238:
036296,000239: 30,3424 03625 FSTEP2 DEC +.1184693815 # 50%
036297,000240: 30,3425 76531 SLOPE2 DEC -.0413889642
036298,000241: 30,3426 16375 01343 VXSTEP2 2DEC +.4529446468 # ABOUT 2898.84 M/S
036299,000242:
036300,000243:
036301,000244:
036302,000245: 30,3430 06275 FSTEP3 DEC +.1990285610 # 84%
036303,000246: 30,3431 06741 SLOPE3 DEC +.2168355662
036304,000247: 30,3432 17033 07603 VXSTEP3 2DEC +.4704127421 # ABOUT 3010.64 M/S
036305,000248:
036306,000249:
036307,000250:
036308,000251: 30,3434 07100 FSTEP4 DEC +.2226276618 # 93%
036309,000252: 30,3435 76601 SLOPE4 DEC -.0389579859
036310,000253: 30,3436 17014 05573 VXSTEP4 2DEC +.4694933687 # ABOUT 3004.75 M/S
036311,000254:
036312,000255:
036313,000256:
036314,000257: 30,3440 37777 HIFSTEP DEC +.9999999999 # JUST IN CASE, ANOMALOUSLY,
036315,000258: 30,3441 00000 HISLOPE DEC +.0000000000 # PREFORCE APPEARS TO
036316,000259: 30,3442 17014 05573 HIVXSTEP 2DEC +.4694933687 # EXCEED 100%.
036317,000260: # * * * * * * * * * * * * * * * * * * * * *
036318,000261:
036319,000262: 30,3444 02565 ETHROTL ECADR ETHROT
End of include-file MASS_CALCULATOR.agc. Parent file is MAIN.agc