3 ms·
It's worth noting that the software, while only 36k machine words long, and the hardware, which was very slow even by the standards of other computers of the 60
by spectre256 13y ago
It's worth noting that the software, while only 36k machine words long, and the hardware, which was very slow even by the standards of other computers of the 60s, were remarkable works created in only a couple years by huge teams (peak of 800 people working on hardware and 400 on software IIRC).
Its popular to dismiss the AGC as simple and uninteresting, but it was a challenging engineering task, and it never once had a failure in flight.
There's lots of resources on the internet to read more. A great book on the topic is Digital Apollo by David Mindell
- NAFV_P 13y ago> Its popular to dismiss the AGC as simple and uninteresting, but it was a challenging engineering task, and it never once had a failure in flight. Stating it never failed in flight is jumping the gun a bit, it didn't fly enough times to get a reliable statistic.
- talmand 13y agoI would think it's accurate to state that the system never had a failure in flight if it never had a failure in flight, despite how many times it flew. If you were to compare it to something else, then how many times it flew becomes important. For example, you can't necessarily say that a 100% success rate over 5 attempts is better than a 95% success rate over 100 attempts.
- spectre256 13y agoRight. I think I remember Digital Apollo quoting an engineer who estimated, based on their extensive ground testing, that the AGC had a MTBF of about 50,000 hours. That's not particularly good, but considering all the Apollo missions spent only about 1000 hours in space total, it was apparently good enough.
- TallGuyShort 13y agoIt never once had a failure in flight, except for the short in Apollo 14, which they managed to hack around mid-flight. Cool story: http://www.ibiblio.org/apollo/#Final_exam_for_the_advanced_student_ http://www.ibiblio.org/apollo/#Final_exam_for_the_advanced_s...
- spectre256 13y agoThat was caused by an actual physical short (in space, conductive bits, usually soldier balls, floating around and shorting things was a big problem), which happened somewhat commonly. I think Apollo 12 nearly aborted the launch because the display was showing all 8s briefly, also caused by a short. However there truly was never an unknown software bug discovered in flight. Lots of known software bugs had workarounds, partially because there was a hard deadline of about 4 months where the software couldn't be changed before the launch. Pretty amazing.
- jfthiigsegbje 13y agoDigital Apollo is a great read.