15 ms·

Source code for the Apollo 11 Guidance Computer

311 points by carljoseph 12y ago

spingsprong 12y ago
http://www.ibiblio.org/apollo/assembly_language_manual.html http://www.ibiblio.org/apollo/assembly_language_manual.html Descriptions of instructions, opcodes, number encoding, etc
drinchev 12y ago
I'm interested what computer languages do they use today for space vehicles? I place my bet on static-type :D ( joke )
- valevk 12y ago
  https://news.ycombinator.com/item?id=4339999 https://news.ycombinator.com/item?id=4339999
  - vans 12y ago
    WOW ! << Do not use direct or indirect recursion. Do not use dynamic memory allocation after task initialization. >> I think they should use COBOL, it's built in :)
    - Jtsummers 12y ago
      Those are standard restrictions for embedded real-time systems, especially if the language itself doesn't offer guarantees on tail-call optimization (like the ML family, Erlang and others do). You have to guarantee the behavior of the program, and recursion (especially unbounded memory usage as in many C implementations) can royally screw things up. You may still have infinite loops because of an error in a for loop's terminating condition, but without dynamic memory and exploding stack usage you'll at least have enough memory left to deal with it when the watchdog timer kicks in.
onion2k 12y ago
I'm surprised to see that it was written in HTML. ;)
deleted 12y ago
[deleted]
DanBC 12y ago
Not quite sure why this links to the code, and not the top level which has a lot more useful information (such as the simulator needed to run the code). http://www.ibiblio.org/apollo/ http://www.ibiblio.org/apollo/ There's some more information here: http://googlecode.blogspot.co.uk/2009/07/apollo-11-missions-40th-anniversary-one.html http://googlecode.blogspot.co.uk/2009/07/apollo-11-missions-...
- bjackman 12y ago
  That's great - I actually came here to say "this is cool in an abstract way but what the fuck am I looking at? I'd love to learn a little bit more about the system". Turns out space folks are great at sharing knowledge! By the way, last night I read the radio transcript from the time Neil and Buzz exited the lunar module: http://www.hq.nasa.gov/alsj/a11/a11.step.html http://www.hq.nasa.gov/alsj/a11/a11.step.html (that site has loads of other Apollo transcripts too). It's annotated and has links to pics and videos. Fascinating.
  - mason240 12y ago
    >Turns out space folks are great at sharing knowledge! I've read that one of the problems a new moon-or-beyond space program would have is that we are so far removed from the Apollo program that all institutional knowledge that was gained is gone because most of the engineers on those projects have passed away.
    - dalke 12y ago
      On the other hand, how much of that institutional knowledge is still useful? Certainly some of it is, but I think experience with the F1-B shows that new knowledge, like 3-D printing, means that parts of the old knowledge aren't needed.
      - NextPerception 12y ago
        I am a mechanical designer by profession and just want to point out that even I who use a 3D printer on a daily basis can't think of any other manufacturing method it has made completely obsolete. It is more like just another tool in my tool belt that adds another way to make something. As with any tool it has it's advantages and it's drawbacks and will only make sense to use it in certain scenarios.
spain 12y ago
http://www.ibiblio.org/apollo/listings/Comanche055/PINBALL_GAME_BUTTONS_AND_LIGHTS.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/PINBALL_G... >Filename: PINBALL_GAME_BUTTONS_AND_LIGHTS.agc Can someone explain what this is? I doubt they had an actual game of pinball in their guidance computer.
- egoebelbecker 12y ago
  It appears to be the code for the controls: # THE KEYBOARD AND DISPLAY SYSTEM PROGRAM OPERATES UNDER EXECUTIVE # CONTROL AND PROCESSES INFORMATION EXCHANGED BETWEEN THE AGC AND THE # COMPUTER OPERATOR. THE INPUTS TO THE PROGRAM ARE FROM THE KEYBOARD, # FROM INTERNAL PROGRAM, AND FROM THE UPLINK. I think it's just someone with a sense of humor.
  - spain 12y ago
    >I think it's just someone with a sense of humor. Yeah I think that's the only explanation for it literally saying "GAME".
  - yellowapple 12y ago
    A rather dark one if "PINBALL GAME" could be interpreted as describing the expected outcome of a lunar landing ;)
  - joezydeco 12y ago
    PINBALL (something flashy with buttons) was a demo. And that demo got us to the moon: "Apparently, nobody had yet arrived at any kind of software requirements for the AGC's user interface when the desire arose within the Instrumentation Laboratory to set up a demo guidance-computer unit with which to impress visitors to the lab. Of course, this demo would have to do something, if it was going to be at all impressive, and to do something it would need some software. In short order, some of the coders threw together a demo program, inventing and using the verb/noun user-interface concept, but without any idea that the verb/noun concept would somehow survive into the flight software. As time passed, and more and more people became familiar with the demo, nobody got around to inventing an improvement for the user interface, so the coders simply built it into the flight software without any specific requirements to do so."[1] [1] http://www.ibiblio.org/apollo/ForDummies.html http://www.ibiblio.org/apollo/ForDummies.html
stuartk 12y ago
In MAIN.agc there is a list of bugger words. Not that I know assembly in any meaningful way, but I've never come across this term before. On Googling, it seems to be something to do with a checksum value?
- sternenseemann 12y ago
  yep, checksums
AmVess 12y ago
Reading the comments is fun...and a bit scary: TC BANKCALL # TEMPORARY, I HOPE HOPE HOPE CADR STOPRATE # TEMPORARY, I HOPE HOPE HOPE
rejectedstone 12y ago
Nice Documentation. I liked this line: 058113,000352: 11,3037 77656 UNIT #PROBABLY UNNECESSARY.
- morsch 12y ago
  Plus ca change... https://github.com/search?l=c&q=%22PROBABLY+UNNECESSARY%22&ref=searchresults&type=Code https://github.com/search?l=c&q=%22PROBABLY+UNNECESSARY%22&r...
Graham24 12y ago
what are bugger codes? http://www.ibiblio.org/apollo/listings/Comanche055/MAIN.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/MAIN.agc....
- sternenseemann 12y ago
  bugger codes is the AGC term for checksums. (see "Playing with Colossus" on this page: http://www.ibiblio.org/apollo/ http://www.ibiblio.org/apollo/)
mrweasel 12y ago
It's of cause fun to have this code to look at, but is it really useful? I don't mean it in a condescending way, but is this actually someone at, say SpaceX, looks at and goes: "Oh so that's how they did that"?
- purringmeow 12y ago
  I don't think so. I believe that code is really tightly coupled with the hardware and at least some part of it covers unique cases. However, these LoC have been written almost 50 years ago! That's truly fascinating.
- mason240 12y ago
  It would be cool to frame and display one them, like one for Automatic Maneuvers. http://www.ibiblio.org/apollo/listings/Comanche055/AUTOMATIC_MANEUVERS.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/AUTOMATIC...
- raverbashing 12y ago
  Probably not. Why? - Today's processors and capabilities run circles around those of the Apollo. It might be interesting to know how they calculate a square root, not today. - They have more sensors and inputs and have to think of new and advanced ways of making it all work together
- jedberg 12y ago
  It's useful in the same way that a historical text is useful -- to see where we came from.
- RogerL 12y ago
  It's achingly beautiful to the pocket protector set (me!). This source code, for example, contains the very first Kalman filter ever used - Kalman was invited over to Moffett field to give talks about his paper, which led to his theory was used in LM code. But I think everyone is very aware of the state of the art at the time, and things have advanced a lot since then. It is impressive to see them cramming that into such a limited processor. But, 'whatever' as to that aspect of it. This is a historical artifact of an amazing feat based on cutting edge research in mathematics/control theory.
NietTim 12y ago
What would it take to make a working simulator from this? Except a whole lot of hardware of course
- burkaman 12y ago
  http://www.ibiblio.org/apollo/index.html http://www.ibiblio.org/apollo/index.html
- argaldo 12y ago
  Ron Burkey has a great simulator that uses the actual code ... http://ibiblio.org/apollo/index.html http://ibiblio.org/apollo/index.html .... here you have an unfinished port of his simulator ( although functional ) for iOS devices ... https://github.com/argaldo/iAGC https://github.com/argaldo/iAGC ... which all of you are greately encouraged to contribute patches .. ;-)
deleted 12y ago
[deleted]
cramerica 12y ago
There are some pretty great comments in here: ALARM_AND_ABORT.agc - http://www.ibiblio.org/apollo/listings/Comanche055/ALARM_AND_ABORT.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/ALARM_AND... TC WHIMPER -1 # YES. DON'T DO POODOO. DO BAILOUT. From the Guidance Computer Data Cards -http://www.ibiblio.org/apollo/CMC_data_cards_15_Fabrizio_Bernardini.pdf http://www.ibiblio.org/apollo/CMC_data_cards_15_Fabrizio_Ber... "POODOO abort, does software restart (ENEMA) and "GO TO POOH" (flashing Verb 37) unless "AVERAGE G" is running then only software restart" From THE_LUNAR_LANDING.agc - http://www.ibiblio.org/apollo/listings/Luminary099/THE_LUNAR_LANDING.agc.html http://www.ibiblio.org/apollo/listings/Luminary099/THE_LUNAR... 033911,000064: 32,3017 06037 FLAGORGY TC INTPRET # DIONYSIAN FLAG WAVING 034090,000243: 32,3241 13247 BZF P63SPOT4 # BRANCH IF ANTENNA ALREADY IN POSITION 1 034091,000244: 034092,000245: 32,3242 33254 CAF CODE500 # ASTRONAUT: PLEASE CRANK THE 034093,000246: 32,3243 04616 TC BANKCALL # SILLY THING AROUND 034094,000247: 32,3244 20623 CADR GOPERF1 034095,000248: 32,3245 16001 TCF GOTOP00H # TERMINATE 034096,000249: 32,3246 13235 TCF P63SPOT3 # PROCEED SEE IF HE'S LYING 034101,000254: 32,3251 04635 TC POSTJUMP # OFF TO SEE THE WIZARD ... 034102,000255: 32,3252 74126 CADR BURNBABY
- JVIDEL 12y ago
  P68 Landing Confirmation section of coding asks the astronaut to load V06N43 (verb/noun) with a great comment of " Astronaut: Now look where you ended up"
- daveslash 12y ago
  I like the note at the top of http://www.ibiblio.org/apollo/listings/Luminary099/BURN_BABY_BURN--MASTER_IGNITION_ROUTINE.agc.html http://www.ibiblio.org/apollo/listings/Luminary099/BURN_BABY... At the get-together of the AGC developers celebrating the 40th anniversary of the first moonwalk, Don Eyles (one of the authors of this routine along with Peter Adler) has related to us a little interesting history behind the naming of the routine. It traces back to 1965 and the Los Angeles riots, and was inspired by disc jockey extraordinaire and radio station owner Magnificent Montague. Magnificent Montague used the phrase "Burn, baby! BURN!" when spinning the hottest new records. Magnificent Montague was the charismatic voice of soul music in Chicago, New York, and Los Angeles from the mid-1950s to the mid-1960s.
EnochSquareRoot 12y ago
OMG. Where's the test coverage?
restlessmedia 12y ago
Tut, where are the supporting unit tests.
hyperliner 12y ago
Wow. This is really impressive: assembler, real-time systems in space, mission-critical equipment, software that protects lives, etc. Maybe that is too much, causing those writing the next "date finding" app to feel incompetent after reading this. But at least we will know we are standing on shoulders of giants.
nsxwolf 12y ago
Do the famous 1201 and 1202 error codes make an appearance here? My assembly skills aren't good enough to find them, I'm afraid.
- thewonderidiot 12y ago
  They do! They're in EXECUTIVE.agc (search for OCT 1201 and OCT 1202). Those error codes mean "No VAC Areas" and "No Core Sets", respectively. Core sets were the basic task control blocks, including each task's entry point, priority, flags, some memory for temporary variables, and a few other things. VAC (Vector Accumulator) areas were a bit more interesting. Most of the real guidance code was not actually written in AGC assembly because it was so primitive and limiting. So, they created the "Interpreter" (INTERPRETER.agc) that's essentially a little virtual machine, that had its own assembly language (complete with mathematical and vector operations). Interpreted tasks needed more than the 7 words of temporary variables provided by the core sets, so they also allocated these VAC areas for more storage. Those error codes showed up on Apollo 11 because of a weird electrical power phasing bug, essentially causing the radar to generate thousands of "interrupts" (actually cycle stealing operations) every second. With all of this additional work, the AGC didn't have enough time to finish its low priority tasks. And since those tasks hadn't exited by the time they were expected to, when the executive attempted to kick off new tasks, it found that no core sets or VAC areas were available, and sounded those program alarms.
- b_emery 12y ago
  Hadn't heard about this but found this link. Great story: http://www.dailykos.com/story/2012/08/25/1124164/-Neil-Armstrong-the-1201-alarm-and-what-it-means-to-be-great http://www.dailykos.com/story/2012/08/25/1124164/-Neil-Armst...
- thret 12y ago
  # Page 1220 # IDLING AND COMPUTER ACTIVITY (GREEN) LIGHT MAINTENANCE. THE IDLING ROUTIEN IS NOT A JOB IN ITSELF, # BUT RATHER A SUBROUTINE OF THE EXECUTIVE. I'm cursed to see spelling errors immediately, and obvious bugs only after hours of frustration.
ghaff 12y ago
Also a lot of of good information in this document: http://www.ibiblio.org/apollo/hrst/archive/1029.pdf http://www.ibiblio.org/apollo/hrst/archive/1029.pdf (Much of the Apollo Guidance Computer and software was developed by the MIT Instrumentation Lab, the predecessor to Draper Lab.)
dmd 12y ago
"arranged for by Deborah Douglas of the MIT Museum" That's my wife's boss; the source material is still sitting on my wife's desk!
rwinn 12y ago
Project Apollo features a near-full implementation of the control panels in the Command Module and Lunar Module, and an increasingly accurate simulation of the internal systems (e.g. electrical distribution, fuel cells). Also the Virtual AGC software is supported, which allows you to run precisely the same on-board guidance software as used by the real Apollo Guidance Computer http://nassp.sourceforge.net/wiki/Main_Page http://nassp.sourceforge.net/wiki/Main_Page
hcrisp 12y ago
Isn't it true that the AGC was initially designed to be the sole navigation computer, but when the implementation did not meet the requirements for accuracy (due to accelerometer and gyroscope drift), they switched to a ground-based radar system? This meant the AGC became the back-up in case the communications system failed. Does anyone know if the AGC was ever used to make a mission-critical decision in the absence of the ground-based radar system? Edit: I think it was actually the PGNCS that was made back-up [1]. Sorry the comment about Kalman filter had me confused. Apparently PGNCS was still used for maintaining orientation, controlling rockets, and navigation during planned outages. 1: http://en.wikipedia.org/wiki/Apollo_PGNCS http://en.wikipedia.org/wiki/Apollo_PGNCS
dang 12y ago
The source code is here: http://www.ibiblio.org/apollo/listings/Comanche055/ http://www.ibiblio.org/apollo/listings/Comanche055/. We changed the url to the top-level page which provides an overview. Edit: see subthread below.
- raldi 12y ago
  Hmm. To me, the appeal of the original link was that, with one click, I could see the entire annotated-with-original-comments source of any part of the AGC. That was really exciting. A simulator (to me at least) is a lot less interesting ... and it's certainly an objectively very different kind of thing. (I for one wouldn't have even bothered clicking the current headline if I hadn't been looking for the original post's comments, which I had seen earlier.) I'm not against curation in general -- it's a crucial aspect of HN, perhaps the crucial aspect. But I do think this particular case was a bit odd.
  - dang 12y ago
    Ok, that's pretty persuasive, especially since most of the comments here are about the code. We changed it back.
kghose 12y ago
If you are into such things, do take a look at the orbiter project (http://orbit.medphys.ucl.ac.uk/ http://orbit.medphys.ucl.ac.uk/) and the NASSP add-on (http://nassp.sourceforge.net/wiki/Main_Page http://nassp.sourceforge.net/wiki/Main_Page). I spent many an after-school night flying to the moon by punching codes on a keyboard. It was amazing. edit: Here's a video https://www.youtube.com/watch?v=7VDV6Gdxakc https://www.youtube.com/watch?v=7VDV6Gdxakc
davegauer 12y ago
For anyone interesting in learning more about this computer system, I highly recommend _Digital Apollo: Human and Machine in Spaceflight_ by David A. Mindell. The hardware limitations! The incredibly low bug count! The memory hand-woven by ladies in a factory! I was blown away by the capabilities of the Apollo computer systems. The craft could have been practically unmanned. Even more impressive, the computers could fly the craft while ALSO being interrupted by and adjusting to human intervention at nearly every step of the process. The pilots and the engineers practically battled over who would be in control of the craft. Fascinating stuff!
analog31 12y ago
I don't know why, but I'm amused by the fact that there's no disclaimer about warranties, express or implied.
vrybas1 12y ago
Story behind the code: TALES FROM THE LUNAR MODULE GUIDANCE COMPUTER http://www.doneyles.com/LM/Tales.html http://www.doneyles.com/LM/Tales.html
marclave 12y ago
This is awesome!
MrBuddyCasino 12y ago
previously: https://news.ycombinator.com/item?id=3888638 https://news.ycombinator.com/item?id=3888638 related: https://news.ycombinator.com/item?id=3336584 https://news.ycombinator.com/item?id=3336584 https://news.ycombinator.com/item?id=6071825 https://news.ycombinator.com/item?id=6071825
Oculus 12y ago
The entire source code was actually woven by wire into memory for the Apollo missions: https://www.youtube.com/watch?v=P12r8DKHsak https://www.youtube.com/watch?v=P12r8DKHsak

311 points by carljoseph 12y ago

http://www.ibiblio.org/apollo/assembly_language_manual.html http://www.ibiblio.org/apollo/assembly_language_manual.html Descriptions of instructions, opcodes, number encoding, etc

drinchev 12y ago

I'm interested what computer languages do they use today for space vehicles? I place my bet on static-type :D ( joke )

valevk 12y ago
https://news.ycombinator.com/item?id=4339999 https://news.ycombinator.com/item?id=4339999
- vans 12y ago
  WOW ! << Do not use direct or indirect recursion. Do not use dynamic memory allocation after task initialization. >> I think they should use COBOL, it's built in :)
  - Jtsummers 12y ago
    Those are standard restrictions for embedded real-time systems, especially if the language itself doesn't offer guarantees on tail-call optimization (like the ML family, Erlang and others do). You have to guarantee the behavior of the program, and recursion (especially unbounded memory usage as in many C implementations) can royally screw things up. You may still have infinite loops because of an error in a for loop's terminating condition, but without dynamic memory and exploding stack usage you'll at least have enough memory left to deal with it when the watchdog timer kicks in.

onion2k 12y ago

I'm surprised to see that it was written in HTML. ;)

deleted 12y ago

[deleted]

DanBC 12y ago

Not quite sure why this links to the code, and not the top level which has a lot more useful information (such as the simulator needed to run the code). http://www.ibiblio.org/apollo/ http://www.ibiblio.org/apollo/ There's some more information here: http://googlecode.blogspot.co.uk/2009/07/apollo-11-missions-40th-anniversary-one.html http://googlecode.blogspot.co.uk/2009/07/apollo-11-missions-...

bjackman 12y ago
That's great - I actually came here to say "this is cool in an abstract way but what the fuck am I looking at? I'd love to learn a little bit more about the system". Turns out space folks are great at sharing knowledge! By the way, last night I read the radio transcript from the time Neil and Buzz exited the lunar module: http://www.hq.nasa.gov/alsj/a11/a11.step.html http://www.hq.nasa.gov/alsj/a11/a11.step.html (that site has loads of other Apollo transcripts too). It's annotated and has links to pics and videos. Fascinating.
- mason240 12y ago
  >Turns out space folks are great at sharing knowledge! I've read that one of the problems a new moon-or-beyond space program would have is that we are so far removed from the Apollo program that all institutional knowledge that was gained is gone because most of the engineers on those projects have passed away.
  - dalke 12y ago
    On the other hand, how much of that institutional knowledge is still useful? Certainly some of it is, but I think experience with the F1-B shows that new knowledge, like 3-D printing, means that parts of the old knowledge aren't needed.
    - NextPerception 12y ago
      I am a mechanical designer by profession and just want to point out that even I who use a 3D printer on a daily basis can't think of any other manufacturing method it has made completely obsolete. It is more like just another tool in my tool belt that adds another way to make something. As with any tool it has it's advantages and it's drawbacks and will only make sense to use it in certain scenarios.

spain 12y ago

http://www.ibiblio.org/apollo/listings/Comanche055/PINBALL_GAME_BUTTONS_AND_LIGHTS.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/PINBALL_G... >Filename: PINBALL_GAME_BUTTONS_AND_LIGHTS.agc Can someone explain what this is? I doubt they had an actual game of pinball in their guidance computer.

egoebelbecker 12y ago
It appears to be the code for the controls: # THE KEYBOARD AND DISPLAY SYSTEM PROGRAM OPERATES UNDER EXECUTIVE # CONTROL AND PROCESSES INFORMATION EXCHANGED BETWEEN THE AGC AND THE # COMPUTER OPERATOR. THE INPUTS TO THE PROGRAM ARE FROM THE KEYBOARD, # FROM INTERNAL PROGRAM, AND FROM THE UPLINK. I think it's just someone with a sense of humor.
- spain 12y ago
  >I think it's just someone with a sense of humor. Yeah I think that's the only explanation for it literally saying "GAME".
- yellowapple 12y ago
  A rather dark one if "PINBALL GAME" could be interpreted as describing the expected outcome of a lunar landing ;)
- joezydeco 12y ago
  PINBALL (something flashy with buttons) was a demo. And that demo got us to the moon: "Apparently, nobody had yet arrived at any kind of software requirements for the AGC's user interface when the desire arose within the Instrumentation Laboratory to set up a demo guidance-computer unit with which to impress visitors to the lab. Of course, this demo would have to do something, if it was going to be at all impressive, and to do something it would need some software. In short order, some of the coders threw together a demo program, inventing and using the verb/noun user-interface concept, but without any idea that the verb/noun concept would somehow survive into the flight software. As time passed, and more and more people became familiar with the demo, nobody got around to inventing an improvement for the user interface, so the coders simply built it into the flight software without any specific requirements to do so."[1] [1] http://www.ibiblio.org/apollo/ForDummies.html http://www.ibiblio.org/apollo/ForDummies.html

stuartk 12y ago

In MAIN.agc there is a list of bugger words. Not that I know assembly in any meaningful way, but I've never come across this term before. On Googling, it seems to be something to do with a checksum value?

sternenseemann 12y ago
yep, checksums

AmVess 12y ago

Reading the comments is fun...and a bit scary: TC BANKCALL # TEMPORARY, I HOPE HOPE HOPE CADR STOPRATE # TEMPORARY, I HOPE HOPE HOPE

rejectedstone 12y ago

Nice Documentation. I liked this line: 058113,000352: 11,3037 77656 UNIT #PROBABLY UNNECESSARY.

morsch 12y ago
Plus ca change... https://github.com/search?l=c&q=%22PROBABLY+UNNECESSARY%22&ref=searchresults&type=Code https://github.com/search?l=c&q=%22PROBABLY+UNNECESSARY%22&r...

Graham24 12y ago

what are bugger codes? http://www.ibiblio.org/apollo/listings/Comanche055/MAIN.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/MAIN.agc....

sternenseemann 12y ago
bugger codes is the AGC term for checksums. (see "Playing with Colossus" on this page: http://www.ibiblio.org/apollo/ http://www.ibiblio.org/apollo/)

mrweasel 12y ago

It's of cause fun to have this code to look at, but is it really useful? I don't mean it in a condescending way, but is this actually someone at, say SpaceX, looks at and goes: "Oh so that's how they did that"?

purringmeow 12y ago
I don't think so. I believe that code is really tightly coupled with the hardware and at least some part of it covers unique cases. However, these LoC have been written almost 50 years ago! That's truly fascinating.
mason240 12y ago
It would be cool to frame and display one them, like one for Automatic Maneuvers. http://www.ibiblio.org/apollo/listings/Comanche055/AUTOMATIC_MANEUVERS.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/AUTOMATIC...
raverbashing 12y ago
Probably not. Why? - Today's processors and capabilities run circles around those of the Apollo. It might be interesting to know how they calculate a square root, not today. - They have more sensors and inputs and have to think of new and advanced ways of making it all work together
jedberg 12y ago
It's useful in the same way that a historical text is useful -- to see where we came from.
RogerL 12y ago
It's achingly beautiful to the pocket protector set (me!). This source code, for example, contains the very first Kalman filter ever used - Kalman was invited over to Moffett field to give talks about his paper, which led to his theory was used in LM code. But I think everyone is very aware of the state of the art at the time, and things have advanced a lot since then. It is impressive to see them cramming that into such a limited processor. But, 'whatever' as to that aspect of it. This is a historical artifact of an amazing feat based on cutting edge research in mathematics/control theory.

NietTim 12y ago

What would it take to make a working simulator from this? Except a whole lot of hardware of course

burkaman 12y ago
http://www.ibiblio.org/apollo/index.html http://www.ibiblio.org/apollo/index.html
argaldo 12y ago
Ron Burkey has a great simulator that uses the actual code ... http://ibiblio.org/apollo/index.html http://ibiblio.org/apollo/index.html .... here you have an unfinished port of his simulator ( although functional ) for iOS devices ... https://github.com/argaldo/iAGC https://github.com/argaldo/iAGC ... which all of you are greately encouraged to contribute patches .. ;-)

deleted 12y ago

[deleted]

cramerica 12y ago

There are some pretty great comments in here: ALARM_AND_ABORT.agc - http://www.ibiblio.org/apollo/listings/Comanche055/ALARM_AND_ABORT.agc.html http://www.ibiblio.org/apollo/listings/Comanche055/ALARM_AND... TC WHIMPER -1 # YES. DON'T DO POODOO. DO BAILOUT. From the Guidance Computer Data Cards -http://www.ibiblio.org/apollo/CMC_data_cards_15_Fabrizio_Bernardini.pdf http://www.ibiblio.org/apollo/CMC_data_cards_15_Fabrizio_Ber... "POODOO abort, does software restart (ENEMA) and "GO TO POOH" (flashing Verb 37) unless "AVERAGE G" is running then only software restart" From THE_LUNAR_LANDING.agc - http://www.ibiblio.org/apollo/listings/Luminary099/THE_LUNAR_LANDING.agc.html http://www.ibiblio.org/apollo/listings/Luminary099/THE_LUNAR... 033911,000064: 32,3017 06037 FLAGORGY TC INTPRET # DIONYSIAN FLAG WAVING 034090,000243: 32,3241 13247 BZF P63SPOT4 # BRANCH IF ANTENNA ALREADY IN POSITION 1 034091,000244: 034092,000245: 32,3242 33254 CAF CODE500 # ASTRONAUT: PLEASE CRANK THE 034093,000246: 32,3243 04616 TC BANKCALL # SILLY THING AROUND 034094,000247: 32,3244 20623 CADR GOPERF1 034095,000248: 32,3245 16001 TCF GOTOP00H # TERMINATE 034096,000249: 32,3246 13235 TCF P63SPOT3 # PROCEED SEE IF HE'S LYING 034101,000254: 32,3251 04635 TC POSTJUMP # OFF TO SEE THE WIZARD ... 034102,000255: 32,3252 74126 CADR BURNBABY

JVIDEL 12y ago
P68 Landing Confirmation section of coding asks the astronaut to load V06N43 (verb/noun) with a great comment of " Astronaut: Now look where you ended up"
daveslash 12y ago
I like the note at the top of http://www.ibiblio.org/apollo/listings/Luminary099/BURN_BABY_BURN--MASTER_IGNITION_ROUTINE.agc.html http://www.ibiblio.org/apollo/listings/Luminary099/BURN_BABY... At the get-together of the AGC developers celebrating the 40th anniversary of the first moonwalk, Don Eyles (one of the authors of this routine along with Peter Adler) has related to us a little interesting history behind the naming of the routine. It traces back to 1965 and the Los Angeles riots, and was inspired by disc jockey extraordinaire and radio station owner Magnificent Montague. Magnificent Montague used the phrase "Burn, baby! BURN!" when spinning the hottest new records. Magnificent Montague was the charismatic voice of soul music in Chicago, New York, and Los Angeles from the mid-1950s to the mid-1960s.

EnochSquareRoot 12y ago

OMG. Where's the test coverage?

restlessmedia 12y ago

Tut, where are the supporting unit tests.

hyperliner 12y ago

Wow. This is really impressive: assembler, real-time systems in space, mission-critical equipment, software that protects lives, etc. Maybe that is too much, causing those writing the next "date finding" app to feel incompetent after reading this. But at least we will know we are standing on shoulders of giants.

nsxwolf 12y ago

Do the famous 1201 and 1202 error codes make an appearance here? My assembly skills aren't good enough to find them, I'm afraid.

thewonderidiot 12y ago
They do! They're in EXECUTIVE.agc (search for OCT 1201 and OCT 1202). Those error codes mean "No VAC Areas" and "No Core Sets", respectively. Core sets were the basic task control blocks, including each task's entry point, priority, flags, some memory for temporary variables, and a few other things. VAC (Vector Accumulator) areas were a bit more interesting. Most of the real guidance code was not actually written in AGC assembly because it was so primitive and limiting. So, they created the "Interpreter" (INTERPRETER.agc) that's essentially a little virtual machine, that had its own assembly language (complete with mathematical and vector operations). Interpreted tasks needed more than the 7 words of temporary variables provided by the core sets, so they also allocated these VAC areas for more storage. Those error codes showed up on Apollo 11 because of a weird electrical power phasing bug, essentially causing the radar to generate thousands of "interrupts" (actually cycle stealing operations) every second. With all of this additional work, the AGC didn't have enough time to finish its low priority tasks. And since those tasks hadn't exited by the time they were expected to, when the executive attempted to kick off new tasks, it found that no core sets or VAC areas were available, and sounded those program alarms.
b_emery 12y ago
Hadn't heard about this but found this link. Great story: http://www.dailykos.com/story/2012/08/25/1124164/-Neil-Armstrong-the-1201-alarm-and-what-it-means-to-be-great http://www.dailykos.com/story/2012/08/25/1124164/-Neil-Armst...
thret 12y ago
# Page 1220 # IDLING AND COMPUTER ACTIVITY (GREEN) LIGHT MAINTENANCE. THE IDLING ROUTIEN IS NOT A JOB IN ITSELF, # BUT RATHER A SUBROUTINE OF THE EXECUTIVE. I'm cursed to see spelling errors immediately, and obvious bugs only after hours of frustration.

ghaff 12y ago

Also a lot of of good information in this document: http://www.ibiblio.org/apollo/hrst/archive/1029.pdf http://www.ibiblio.org/apollo/hrst/archive/1029.pdf (Much of the Apollo Guidance Computer and software was developed by the MIT Instrumentation Lab, the predecessor to Draper Lab.)

dmd 12y ago

"arranged for by Deborah Douglas of the MIT Museum" That's my wife's boss; the source material is still sitting on my wife's desk!

rwinn 12y ago

Project Apollo features a near-full implementation of the control panels in the Command Module and Lunar Module, and an increasingly accurate simulation of the internal systems (e.g. electrical distribution, fuel cells). Also the Virtual AGC software is supported, which allows you to run precisely the same on-board guidance software as used by the real Apollo Guidance Computer http://nassp.sourceforge.net/wiki/Main_Page http://nassp.sourceforge.net/wiki/Main_Page

hcrisp 12y ago

Isn't it true that the AGC was initially designed to be the sole navigation computer, but when the implementation did not meet the requirements for accuracy (due to accelerometer and gyroscope drift), they switched to a ground-based radar system? This meant the AGC became the back-up in case the communications system failed. Does anyone know if the AGC was ever used to make a mission-critical decision in the absence of the ground-based radar system? Edit: I think it was actually the PGNCS that was made back-up [1]. Sorry the comment about Kalman filter had me confused. Apparently PGNCS was still used for maintaining orientation, controlling rockets, and navigation during planned outages. 1: http://en.wikipedia.org/wiki/Apollo_PGNCS http://en.wikipedia.org/wiki/Apollo_PGNCS

dang 12y ago

The source code is here: http://www.ibiblio.org/apollo/listings/Comanche055/ http://www.ibiblio.org/apollo/listings/Comanche055/. We changed the url to the top-level page which provides an overview. Edit: see subthread below.

raldi 12y ago
Hmm. To me, the appeal of the original link was that, with one click, I could see the entire annotated-with-original-comments source of any part of the AGC. That was really exciting. A simulator (to me at least) is a lot less interesting ... and it's certainly an objectively very different kind of thing. (I for one wouldn't have even bothered clicking the current headline if I hadn't been looking for the original post's comments, which I had seen earlier.) I'm not against curation in general -- it's a crucial aspect of HN, perhaps the crucial aspect. But I do think this particular case was a bit odd.
- dang 12y ago
  Ok, that's pretty persuasive, especially since most of the comments here are about the code. We changed it back.

kghose 12y ago

If you are into such things, do take a look at the orbiter project (http://orbit.medphys.ucl.ac.uk/ http://orbit.medphys.ucl.ac.uk/) and the NASSP add-on (http://nassp.sourceforge.net/wiki/Main_Page http://nassp.sourceforge.net/wiki/Main_Page). I spent many an after-school night flying to the moon by punching codes on a keyboard. It was amazing. edit: Here's a video https://www.youtube.com/watch?v=7VDV6Gdxakc https://www.youtube.com/watch?v=7VDV6Gdxakc

davegauer 12y ago

For anyone interesting in learning more about this computer system, I highly recommend _Digital Apollo: Human and Machine in Spaceflight_ by David A. Mindell. The hardware limitations! The incredibly low bug count! The memory hand-woven by ladies in a factory! I was blown away by the capabilities of the Apollo computer systems. The craft could have been practically unmanned. Even more impressive, the computers could fly the craft while ALSO being interrupted by and adjusting to human intervention at nearly every step of the process. The pilots and the engineers practically battled over who would be in control of the craft. Fascinating stuff!

analog31 12y ago

I don't know why, but I'm amused by the fact that there's no disclaimer about warranties, express or implied.

vrybas1 12y ago

Story behind the code: TALES FROM THE LUNAR MODULE GUIDANCE COMPUTER http://www.doneyles.com/LM/Tales.html http://www.doneyles.com/LM/Tales.html

marclave 12y ago

This is awesome!

MrBuddyCasino 12y ago

previously: https://news.ycombinator.com/item?id=3888638 https://news.ycombinator.com/item?id=3888638 related: https://news.ycombinator.com/item?id=3336584 https://news.ycombinator.com/item?id=3336584 https://news.ycombinator.com/item?id=6071825 https://news.ycombinator.com/item?id=6071825

Oculus 12y ago

The entire source code was actually woven by wire into memory for the Apollo missions: https://www.youtube.com/watch?v=P12r8DKHsak https://www.youtube.com/watch?v=P12r8DKHsak