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This is why I cleverly have no RAM
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this post was submitted on 02 Oct 2023
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People also forget that most of the actual calculations were done on paper first; the computers were basically just executing precalculated instructions.
This is the stack of code used for the navigation software for the Apollo program.
(Fun fact: standing next to it is Margaret Hamilton, director of NASA's Software Engineering Division & the lead of the team who wrote that code.)
Additional fun fact: Margaret Hamilton is the person who coined the term "software engineering"
Ooh, I didn't know that. That is a fun fact! 😁
These are multiple printouts of the code. The computer did not only execute precalculated instruction. (This would be a sequencer BTW.). Try it yourself AGC.
That is pretty cool. I might try it tonight since I'm at work right now. Thanks!
Though, to be fair, I did say that most of the code was precalculated.
I'm not quite sure if even that is correct. The AGC, as far as I understand it, did do quite a bit of calculation on the fly and was essentially the first digital fly by wire system. It did rely on input from the crew and ground control for eg correcting its state vector etc etc, but it even has dedicated vector instructions if I recall correctly. Can't really precompute all that much when you can't be sure things will go to plan and you're dealing with huge distances. It did have eg separate programs for different phases of the flight but they weren't really precalculated as such, more like different modes that eg read input from different sensors etc etc.
The US space program was pretty big on having a human in the loop though, much more so than the Soviet one which relied more on automation and the pilot was more of a passenger in a sense, sort of a failsafe for the automatic systems.
The book Digital Apollo goes into all this this in more detail, I can highly recommend it if you're a ginormous nerd like I am and think that computers we've shot into space are endlessly fascinating
I didn't know that. Thanks for telling me! I'll have to check out that book. It sounds fascinating. :)