11 HN users recommended this lecture11 months2021–2026score 14
Years with an HN recommendation, 2007–2026
HN calls it mandatory viewing on the AGC, praising the speaker's enthusiasm and the clear account of restartable, robust software design.
Robert Wills of TNMoC explains the Apollo Guidance Computer hardware and software, then walks through the Apollo 11 landing procedure step by step, including the 1202 alarms.
“The guy is really, really into it and it just makes the presentation amazing.” (HN, 2022)
I suggest watching this excellent presentation: [this video] . He goes in to great depth in explaining how the LEM was in fact capable of landing itself. Automation was widespread in the development and execution of the Apollo program.
Yeah, a great example is this presentation[1] about the Apollo guidance computer. The guy is really, really into it and it just makes the presentation amazing. [1] [this video]
That reminds me of the Apollo guidance computer talk (available on youtube [this video] ). "Everyone" might have seen this one, but if one hasn't, it's a gem.
I can't recommend a book, but I watched this video a while ago, and I found it riveting: "Light Years Ahead | The 1969 Apollo Guidance Computer" [0] > Robert Wills introduces the amazing hardware and software that made up the Apollo Guidance Computer, walks you through the landing procedure step-by-step, and talks about the pioneering design principles that were used to make the landing software robust against any failure. [0] [this video]
Walks through landing procedure and robust software design.
A bit offtopic but I recently saw a surprisingly interesting talk about the Apollo board computer[0], and it's incredible how carefully they engineered the whole thing. Software hardcoded in the wiring, error correction for every memory access, ability to restart the whole system in any situation without losing state...this thing might have been rudimentary in today's standards, but the quality of the software was a different beast. [0] [this video]
Apollo computer's careful engineering: wired software, error correction, restartability.
The AGC is a fascinating device. It used 60% of the ICs produced in the United States in 1963. If you are interested in the AGC I suggest this excellent video: [this video] .
Here's another lecture I really enjoyed walking through the operation of the guidance computer and the events that lead to the 1202 error, which the speaker sums up as an "out of memory" error resulting in an automatic reboot. He says the cause was a hardware bug taxing the machine with empty status updates, combined with Buzz typing "verb 16 noun 68" to have the display auto-update some stats - he was crashing the machine but didn't put together why it was happening because it never crashed the machine in simulation. [this video]
Walkthrough of operation and cause of the 1202 error.
Theres a great video of a talk on the AGC from Robert Wills at England's The National Museum of Computing [this video] More info and links to other videos on [link]
> Apollo 11 had problems with the LM guidance computer, but was saved by Neil Armstrong's piloting skill. This is a common misconception but mixes up at least three things. 1) Yes, Eagle was long, but not because of a software bug. The exact reason is unclear and there may have been multiple factors. 2) Yes, there were unexpected computer alarms but these were caused by a hardware bug that manifested because a switch was in an unexpected position. The software handled this appropriately. Margaret Hamilton said: “To blame the computer for the Apollo 11 problems is like blaming the person who spots a fire and calls the fire department. Actually, the computer was programmed to do more than recognize error conditions. A complete set of recovery programs was incorporated into the software. The software's action, in this case, was to eliminate lower priority tasks and re-establish the more important ones. The computer, rather than almost forcing an abort, prevented an abort. If the computer hadn't recognized this problem and taken recovery action, I doubt if Apollo 11 would have been the successful Moon landing it was.” 3) Neil Armstrong did adjust the landing point late in the descent after noticing rough terrain. He utilized semi-automatic control to do this. Essentially adjusting the target point for the autopilot. Eagle wasn’t directly flown like an aircraft. [link] A great video on the AGC and Apollo 11 landing: [this video]
I love the calm communications. The feeling of everything possible thought out. Regarding moon landing videos, I also enjoyed the "story" of the computer on board which is told in this great presentation [1]: Light Years Ahead | The 1969 Apollo Guidance Computer by Robert Wills. Definitely worth a watch if you fancy the moon landing. [1]: [this video]
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