LGC Simulator


In the workshop (April 2005):  The Lunar Module Systems simulator.  Will provide a detailed, flyable, system level simulation of all LM systems and panels.  Currently comprises LGC, AGS (inc. DEDA and AEA), EPS, EDS, Lighting, some DPS, some telemetry, some RCS.  I probably won't release this publicly until most of the work has been completed, email me for further information or if you would like to be emailed when the public release is available.

Some images (approx 200Kb each) are available (note that some instruments on panels 1 and 2 still just have placeholding graphics) :

Panels 1, 2 and 3

DSKY and part of Panel 3

DEDA (displaying time in 1/10th minutes) and part of Panel 12

ORDEAL, explosive devices etc.

Currently in flight (Sept 2004):

After several months of work a simulation of a Block II Apollo Guidance Computer running the original Luminary 1C program is now available.  You can download it here (approx. 6Mb).  The current readme file is shown below.

This version was presented at the MAPLD 2004 conference in Washington DC Sept 8-10, 2004, as part of a day-long series of talks by AGC engineers and managers and current researchers and historians.

Apollo Guidance Computer (Block II) Simulator

Version 1.2.2 - Sep 2004

Simulates Block II Apollo Guidance Computer 46 (C-30) and Luminary 1C (131) approximately as used on Lunar Module 7 (Apollo 13)

Copyright (c) 2004/5 University of the West of England, Bristol

This software is freely available for educational use, but please contact me and let me know what you intend using it for!

Author: Julian Webb - julian2.webb@uwe.ac.uk

Website: http://www.cems.uwe.ac.uk/~jtwebb/agc


- Windows XP
- Approx. 1.5Mb free disk space
- Almost any processor/memory should be capable of running the simulation, though best results are obtained with  >1GHz clock speed
- NB - See JOYSTICK section below for notes on using a joystick with the simulator


This software is currently under development and you use it at your own risk. Though not aware of any problems, the author takes no responsibility for any problems it may cause to your computer hardware or software.


1. Unzip AGC.zip distribution files to a temporary folder
2. Run setup.exe from AGC setup folder
3. Follow usual installation prompts
4. Default installation is to c:\Program Files\AGC
5. To start simulator execute "runagc.exe" (NOT "agc.exe" - this is the computer itself)
6. The application should start - numerous forms (detailed below) will appear and minimise and the DSKY should appear
7. If a screen labelled "RCS" appears see the JOYSTICK section below for help
8. After a few seconds a command prompt window will appear on the Windows Start Bar - it should be explained that the AGC loads (after allowing 5 secs after starting) a pad file (pad0.txt) that loads certain values into erasable memory.
9. If the yellow "PROG" warning light appears on the DSKY, press the RSET key (the reason for this is that the simulator starts with an empty memory. On startup, the LUminary program checks to see if this is a restart from a previous shutdown. It does this by summing two memory locations that are complements of each other. If the result is not -0 (the AGC uses modified one-complement arithmetic), it assumes the memory has been corrupted and generates error 1107, resulting in the PROG light)
10.The simulator adapts its speed to your processor within 5 seconds and then monitors the AGC throughput every 10 seconds
11.Click on DSKY keys to press them. Some of the switches and circuit breakers are operational - click them to alter.
12.To exit the simulator, close the main application window - this also unloads the AGC command window



Apollo Optical Telescope - used for fine-aligning the IMU. Current simulation includes rotatable reticle (click on top or bottom of the vertical edge-on knob (clicking on the end of the knob rotates the reticle by 10 degrees, clicking closer to the centre by 1 deg). The amount of reticle rotation is recorded in the AOT counter. The red dots are reticle faults. The three pushbuttons (Mark X, Mark Y and REJECT) are operational but not tested yet.
Currently, detent positions are not operational. Starfields are not yet implemented.


Runs demonstration scripts. Select the desired script form the selection list and click START. Demos repeat when they reach the end. Use STOP to pause the demo. Deselecting the auto-run option displays a prompt after each demo step, rather than using the built-in waits.

New demos (and new versions of the simulator) will be available via the AGC website (see above).

The scripting language used is self-explanatory. If you write any demo scripts yourself, I'd appreciate a copy!


The top, white, box shows the 200 word telemetry downlink frame. The lower, green-text, section shows some of the more useful details, including the downlinked DSKY display.


In two parts. The main DSKY display and keyboard is self-explanatory. One point to note is that the PRO(ceed) key, unlike all the other keys, sends a discrete signal to the AGC. Therefore it is necessary to hold down PRO for an appreciable length of time (c. 1s).

To the right are various switches and circuit breakers. Some of these work and some are just placeholders for future development. The most important is the IMU OPR cb that starts the ISS/IMU. No attempt has been made to simulate the actual LM cockpit environment, though groups of switches are the same as in the original.


Some simple fault-generating options - this form is under development at present (Aug 2004)


Also under development, this form displays the internal status of the IMU. Currently displayed are the gyro speeds and the CDU angles. The IMU supports startup (i.e. depressing the IMU OPR CB) and shutdown, IMU Coarse Align and Zero CDU Angles. Further functionality will be added as required.


Displays the list of jobs scheduled by the executive and the waitlist (used for short functions).


Appears automatically when any RCS jets are firing and displays a graphic LM ascent stage to show firing of the jets. This can be demonstrated (without a joystick) by closing the ATT DIR CONT circuit breaker and pressing the +X TRANSL button on the DSKY form.


Intended for my use! Dumps some internal, shared, data in top field. Lower field shows (rather more usefully) the settings of most AGC channels, updated every 1ms.


Currently two options:
By instruction(default) : Displays graphical representation of either instruction count or machine cycle times (MCT) for each instruction, sorted by count. Display can be halted/restarted and the count reset to zero.
By section: As above but displays instructions/MCT by each logical program section

NB: displayed X-axis text indicates that a non-zero count exists for that item.


Very limited support for joysticks is provided. The LM had two three-axis controllers - so it is not that easy to duplicate this in a convenient, transportable way, with off-the-shelf hardware. The system is set up to use a Saitek P880 gamepad (I don't suggest you get one of these as the current functionality is quite restricted). If you have problems with the RCS form appearing, you can just rename the "joystick.def" file - this will inhibit any joystick checking on the part of the simulator. If you want to know about using other joysticks, email me!

Later versions of the simulator will include a full simulation of the RCS control systems.


1. The standby program P06 causes the AGC program to close after the PRO key is pressed after checklist is displayed.
2. A V36 restart causes the LM weight to be overwritten.


- (See 'In the workshop' at top of page)


Do you or your organisation have any (unpublished, non-confidential) information relating to early spacecraft inflight computers? Please email me if you would be prepared to have the material copied and made available to a wider research community. I am particularly interested in the AGC (of course!) and the AEA (the computer in the LM Abort Guidance Section).

Frank O'Brien for supplying copies of many interesting documents

Ron Burkey for allowing checking of the transcription of Luminary 1C and for publishing details of the hitherto little known AEA.  Visit his excellent Apollo site at: http://www.ibiblio.org/apollo/

Hugh Blair-Smith for interesting and illuminating discussions

Capt John Young for saying 'Well, I'll be...' when shown the simulator


  ( visitors to this page since 18 Feb 2004)

Page maintained by Julian Webb 2004 University of the West of England, Bristol