Original Apollo 11 guidance computer (AGC) source code

[pgp_protector]

Came through my work feed today, Thought I'd share for those that like the History of the Apollo Launches.

http://www.ibiblio.org/apollo/

Git Hub link -> https://github.com/chrislgarry/Apollo-11

 

[timewerx]

Came through my work feed today, Thought I'd share for those that like the History of the Apollo Launches.

http://www.ibiblio.org/apollo/

Git Hub link -> https://github.com/chrislgarry/Apollo-11

I like the Apollo Launches but Assembly code, ugghh!

The time I "author" assembly codes is the time I succeeded in making an AI that can code in assembly!

 

[FrumiousBandersnatch]

Came through my work feed today, Thought I'd share for those that like the History of the Apollo Launches.

http://www.ibiblio.org/apollo/

Git Hub link -> https://github.com/chrislgarry/Apollo-11

Thanks for that, fascinating - I remember reading about the Apollo guidance computers and software (IIRC the first multi-tasking time-sharing OS?) and the LEM guidance computer that threw up those 1202 task-dump errors because the other radar had been left on during the descent.

Interesting to see early assembler code again - the last serious assembler coding I did was a hand port of the Sargon Chess program from 6502 assembler to Z80 (for my NASCOM II). Took me days...

 

[Chesterton]

Would the Apollo missions have been possible without a computer? Did AGC make things a lot easier, or was it absolutely essential?

 

[timewerx]

Would the Apollo missions have been possible without a computer? Did AGC make things a lot easier, or was it absolutely essential?

I think it was Buzz Aldrin who said that they were "essentially passengers" and the Apollo Flight was being flown by the computer most of the time.

From the Apollo 13 film, and watching many Apollo missions footage on youtube, it would seem that under an accident-free mission, the astronauts only managed the main engines (basically when to turn on and off the main engines), manually flew the Command and Service (C&S) modules when docking to the Lunar Excursion Module (LEM), Manually flown the touchdown of the LEM, and finally, the initial stages of reentry.

They seem to be flipping switches a lot more than joystick-banging.... It's the same thing you do if you're operating a computer...

Thus, it seems the computer is in control most of the time. If that's not enough, the astronauts also depended on the computer's calculations to help them fly the machine.

Unmanned Surveyor space probes which preceded the Apollo moon missions made the entire flight to a soft landing on the moon under computer control.

It is absolutely essential. A lot of things could go wrong in a manned space flight. It would certainly be wise to reduce pilot error by reducing the workload of the pilot (Even jet airliners are flown by the computer most of the time!)

NASA simply did it for national pride, vanity, morale, etc. For the Cold War....

If it weren't for this pride contest with the USSR, or simply the pride of sending people to space, robotic probes could have done the job way more efficiently even for the purpose of delivering moon rocks to Earth. Lots of money that could be saved for bigger space projects later on. Sigh....

 

[Eudaimonist]

I used to program in Assembler. Some in 6502, and some in 80286.

Fun, fun, but only for Real Programmers.


eudaimonia,

Mark

 

[Chesterton]

It is absolutely essential. A lot of things could go wrong in a manned space flight. It would certainly be wise to reduce pilot error by reducing the workload of the pilot (Even jet airliners are flown by the computer most of the time!)

I agree of course, but I'm asking would it actually be at all humanly possible to do it without a computer?

I'm thinking of this incident on Apollo 8, and it's really interesting that they used stars for navigation as a sea sailing ship would have thousands of years before:

Later, Lovell used some otherwise idle time to do some navigational sightings, maneuvering the module to view various stars by using the computer keyboard. However, he accidentally erased some of the computer's memory, which caused the Inertial Measurement Unit (IMU) to think the module was in the same relative position it had been in before lift-off and fire the thrusters to "correct" the module's attitude.

Once the crew realized why the computer had changed the module's attitude, they realized they would have to re-enter data that would tell the computer its real position. It took Lovell ten minutes to figure out the right numbers, using the thrusters to get the stars Rigel and Sirius aligned, and another 15 minutes to enter the corrected data into the computer.
​

- from Wiki

 

[rockytopva]

Apollo 11 Launch!

 

[timewerx]

I agree of course, but I'm asking would it actually be at all humanly possible to do it without a computer?

The Apollo 13 crew did it with course corrections on the return trip. They had to turn off the computer to save electricity, calculate the course corrections literally on paper, and fly the ship manually to make the course corrections.

Manual flight in space is humanly possible with adequate instrumentation, but you'll be taking a huge amount of risk, especially with a tiny margin of error. In addition, you'd be wasting precious fuel.

Every attitude changes you make in space, every course correction uses fuel. It is extremely difficult to keep a rocket firmly pointed in one direction without any computerized stabilization.

You can try but the computer will always make precise corrections, thus, far fewer corrections required - which saves fuel.

And finally, the computer automating many aspects of space flight help reduce crew fatigue - a LOT!

The Apollo project pushed the limits of electronic computing at that time and for very good reasons.

Once the crew realized why the computer had changed the module's attitude, they realized they would have to re-enter data that would tell the computer its real position. It took Lovell ten minutes to figure out the right numbers, using the thrusters to get the stars Rigel and Sirius aligned, and another 15 minutes to enter the corrected data into the computer.

Sweet! But if such mistake happened prior to re-entry, they would have to abort but if they didn't have enough fuel to abort, they would have likely ended up in million pieces over the Pacific.

Such is the importance of computers and automation of space flight that even the world's finest prefer to be flying with it.

 

[Oafman]

There are some easter eggs in the code, which people have noticed since it was released:

Don't let anybody tell you that programmers don't know how to have fun......

 

[timewerx]

Don't let anybody tell you that programmers don't know how to have fun......

Ironically, I did something quite like that in my programming days. Shortly after, I was taken from development. Might as well sabotaged my career.

Btw, those messages won't appear in the computer. Only visible in the source code and the astronauts would never have seen those messages.

 

[FrumiousBandersnatch]

There are some easter eggs in the code, which people have noticed since it was released:

Don't let anybody tell you that programmers don't know how to have fun......

Note the change log says Apollo software engineer Don Eyles named the function - here's an article about the LEM source code (and those notorious 1201 & 1202 errors), with a video of Don running through his paper copy