https://github.com/virtualagc/virtualagc
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Tip revision: 0cfe36b
GIMBAL_LOCK_AVOIDANCE.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: GIMBAL_LOCK_AVOIDANCE.agc
## Purpose: Part of the source code for Luminary 1A build 099.
## It is part of the source code for the Lunar Module's (LM)
## Apollo Guidance Computer (AGC), for Apollo 11.
## Assembler: yaYUL
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo.
## Pages: 364
## Mod history: 2009-05-17 RSB Adapted from the corresponding
## Luminary131 file, using page
## images from Luminary 1A.
## 2010-12-31 JL Fixed page number comment.
## 2016-12-14 RSB Proofed text comments with octopus/ProoferComments
## but no errors found.
## 2017-08-22 RSB Fixed comment-text typo identified in ZERLINA 56.
##
## This source code has been transcribed or otherwise adapted from
## digitized images of a hardcopy from the MIT Museum. The digitization
## was performed by Paul Fjeld, and arranged for by Deborah Douglas of
## the Museum. Many thanks to both. The images (with suitable reduction
## in storage size and consequent reduction in image quality as well) are
## available online at www.ibiblio.org/apollo. If for some reason you
## find that the images are illegible, contact me at info@sandroid.org
## about getting access to the (much) higher-quality images which Paul
## actually created.
##
## Notations on the hardcopy document read, in part:
##
## Assemble revision 001 of AGC program LMY99 by NASA 2021112-61
## 16:27 JULY 14, 1969
## Page 364
BANK 15
SETLOC KALCMON1
BANK
# DETECTING GIMBAL LOCK
LOCSKIRT EQUALS NOGIMLOC
NOGIMLOC SET
CALCMAN3
WCALC LXC,1 DLOAD*
RATEINDX # CHOOSE THE DESIRED MANEUVER RATE
ARATE,1 # FROM A LIST OF FOUR
SR4 CALL # COMPUTE THE INCREMENTAL ROTATION MATRIX
DELCOMP # DEL CORRESPONDING TO A 1 SEC ROTATION
# ABOUT COF
DLOAD* VXSC
ARATE,1
COF
STODL BRATE # COMPONENT MANEUVER RATES 45 DEG/SEC
AM
DMP DDV*
ANGLTIME
ARATE,1
SR
5
STORE TM # MANEUVER EXECUTION TIME SCALED AS T2
SETGO
CALCMAN2 # 0(OFF) = CONTINUE MANEUVER
NEWANGL +1 # 1(ON) = START MANEUVER
# THE FOUR SELECTABLE FREE FALL MANEUVER RATES SELECTED BY
# LOADING RATEINDX WITH 0, 2, 4, 6, RESPECTIVELY
ARATE 2DEC .0088888888 # = 0.2 DEG/SEC $ 22.5 DEG/SEC
2DEC .0222222222 # = 0.5 DEG/SEC $ 22.5 DEG/SEC
2DEC .0888888888 # = 2.0 DEG/SEC $ 22.5 DEG/SEC
2DEC .4444444444 # = 10.0 DEG/SEC $ 22.5 DEG/SEC
ANGLTIME 2DEC .0001907349 # = 100B-19 FUDGE FACTOR TO CONVERT
# MANEUVER ANGLE TO MANEUVER TIME