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Perhaps of relevance to Hacker News: Four minutes before the moon landing, the Apollo Guidance Computer began throwing 1202 and 1201 alarms - indicating that i
by trothamel 12y ago
Perhaps of relevance to Hacker News:
Four minutes before the moon landing, the Apollo Guidance Computer began throwing 1202 and 1201 alarms - indicating that it wasn't completing its processing loop in time.
Here's the audio from the flight director and guidance loops, as they troubleshooted the problem in real time, clearing Apollo 11 to land.
http://forum.nasaspaceflight.com/index.php?topic=35230.0 http://forum.nasaspaceflight.com/index.php?topic=35230.0
- daigoba66 12y agoAnd I thought zero-downtime web app deployments were stressful... this really puts stuff into perspective.
- ProAm 12y agoIt's embarrassing that web apps have has much downtime as they do given the processing power they are given.
- davidw 12y agoIt actually makes sense given the economics of the situation: time invested in high availability is a poorer use of resources than, say, adding features for most web sites. We can make web sites that stay up, always. It's just that it costs a lot more and / or they do less.
- thezach 12y agoOddly enough Google is throwing an error on that file.... to many people downloading the file recently.
- trothamel 12y agoI've rehosted it here: http://share.rothamel.us/Apollo_11_Landing.mp3 http://share.rothamel.us/Apollo_11_Landing.mp3
- ryangee 12y agoThis is definitely the best way to listen to the audio: http://www.firstmenonthemoon.com/ http://www.firstmenonthemoon.com/
- helicon 12y agothis is amazing
- deleted 12y ago[deleted]
- ArkyBeagle 12y agoBecause there was no text chat then. BBN was contracted to build the first four IMP machines in 1969.
- dm2 12y agoWe put someone on the moon before we invented text-chat? Wow.
- thefreeman 12y agoSeeing as the computers were spitting error numbers instead of error messages, I am guessing that wasn't an option at that time with the hardware they had.
- ArkyBeagle 12y agoJack Garman had hand-written down all the trouble codes on a "cheat sheet". He's the one who called "go". I am not even sure if the MIT software team knew what 1201 and 1202 were. The AGC was one of the first to use priority multitasking. The 1201 and 1201 faults were indication that lower priority tasks were getting yanked. See "Moon Machines". Seriously.
- dm2 12y agoWhat would be an example of a lower-priority task in this situation? A couple of links to the videos you mentioned: http://www.sciencechannel.com/video-topics/space-videos/moon-machines.htm http://www.sciencechannel.com/video-topics/space-videos/moon... The above is probably one of the most informative 2 minute videos I've ever seen. https://www.youtube.com/watch?v=DWcITjqZtpU&list=PL7E69228169F0FA1B https://www.youtube.com/watch?v=DWcITjqZtpU&list=PL7E6922816... "there were no specs, we made it up" "if you screwed up you got a stack of papers that was 2 feet thick" "the overall memory for the Apollo guidance computer was 72 kilobytes" https://www.youtube.com/channel/UClDdlBdSzrWIUijnnUDXobw https://www.youtube.com/channel/UClDdlBdSzrWIUijnnUDXobw https://www.youtube.com/channel/UCNpdHqZ5OmFOnICpZz4Mflw https://www.youtube.com/channel/UCNpdHqZ5OmFOnICpZz4Mflw
- ArkyBeagle 12y agoOops - display and keypad. See above :)
- XorNot 12y agoClicked into the first one and got a thing about the insulation between the tanks - the 3rd video in the playlist was about them hiring surfboard makers to do the honeycomb insulation between the fuel tanks, since they had more experience working with the materials in the heat conditions. Just another kind of "the space program was amazing" thing - the sheer diversity of people who got hired on to contribute is continually surprising. An amazing tribute to the pragmatism of NASA under the conditions.
- ArkyBeagle 12y agoDisplay and keypad as I recall. The problem was actually a deployment problem. The checklist for configuring the computer left a diagnostic mode on that sucked up a lot of CPU.
- timothya 12y agoSome more information on the 1202 and 1201 alarms: http://www.hq.nasa.gov/alsj/a11/a11.1201-pa.html http://www.hq.nasa.gov/alsj/a11/a11.1201-pa.html tl;dr: Some misconfigured switches meant that rendezvous radar jobs kept being erroneously scheduled, which used up available memory. Whenever there was no more memory available, the alarm would fire and the computer was rebooted. It would immediately restart (resuming from near where they left off) all the high priority jobs (while not restarting the radar jobs), meaning that it could still land safely.