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> Apollo 11 spacecraft contains 4 computers Analog computers don't get the respect they deserve. There's one more computer, the FCC. The Flight Control Comput
by kens 3y ago
> Apollo 11 spacecraft contains 4 computers
Analog computers don't get the respect they deserve. There's one more computer, the FCC. The Flight Control Computer is an analog computer in the Saturn V that controlled the rocket gimbals. It's a two-foot cylinder weighing almost 100 pounds.
- nothercastle 3y agoExactly this. A lot of the systems had built in analog computers. It’s a lot cheaper to build then now with electronics but you need more computing power to do things that were previously done mechanically
- hinkley 3y agoAnalog computers have to be rebuilt if it turns out the program is wrong though, don’t they?
- nothercastle 3y agoYes though they tend to be mechanically tuned. So like a pneumatic computer or will get tuned to operate into some range of inputs and you probably bench prototype it before you mass produce it
- coder543 3y agoIn the context of this thread, I believe even a digital computer would have to be rebuilt if the program is wrong... :P Unless you typically salvage digital computers from the wreckage of a failed rocket test and stick it in the next prototype. If the FCC is wrong, kaboom.
- scaredginger 3y agoI'm pretty sure you can perform tests and find defects without actually flying the rocket
- deleted 3y ago[deleted]
- Tommstein 3y agoPresumably they meant a program being discovered to be wrong before the computer was actually launched. And meant literally building a whole new computer, not just recompiling a program.
- hinkley 3y agoYeah, though to be fair, some of the programs Apollo ran were on hand woven ROMs, so I may be making too fine a distinction. The program itself was built, not compiled. It if we are comparing with today, it would just be installed, not constructed.
- KMag 3y agoFor the Apollo Guidance Computer, changing the program meant manually re-weaving wires through or around tiny magnet rings. A good part of the cost of the computer was the time spent painstakingly weaving the wires to store the program.
- neodypsis 3y agoThere's a very nice video about the assembly lines MIT made just for building the Apollo computer [0]. 0. https://www.youtube.com/watch?v=ndvmFlg1WmE https://www.youtube.com/watch?v=ndvmFlg1WmE
- denton-scratch 3y agoPardon me, but why would you have to re-weave wires around magnetic rings? The magnetic rings are for storing data; the whole point is that you can change the data without rewiring the memory. If you have to re-wire permanent storage (e.g. program storage), that's equivalent to creating a mask ROM, which is basically just two funny-shaped sheets of conductor. There's no need for magnetic rings.
- KMag 3y agoNo, I'm not talking about magnetic core memory. Core rope memory also used little magnetic rings. https://en.wikipedia.org/wiki/Core_rope_memory https://en.wikipedia.org/wiki/Core_rope_memory input wires were energized, and they were coupled (or not) to the output wires depending on if they shared a magnetic ring (or not).
- nothercastle 3y agoI had assumed it meant more simple things like balanced balancing pneumatic or mechanical components that always put you at the the correct ratio sort of like a carburetor vs fuel injection.
- gumby 3y agoTypically they were reprogrammed by changing the jumpers. The analogous digital change would be replacing the band of cards in a jaquard loom. Much less than “rebuilding”. There have been some hybrids too.
- KRAKRISMOTT 3y agoYou forgot the most important one, the human computers at ground control. Who said women can't do math? https://www.smithsonianmag.com/science-nature/history-human-computers-180972202/ https://www.smithsonianmag.com/science-nature/history-human-...
- mulmen 3y ago> Who said women can't do math? The straw man?
- legostormtroopr 3y agoStraw person?
- canadianfella 3y ago[dead]
- asylteltine 3y ago> Who said women can't do math? Nobody
- shermantanktop 3y agoA quick search will show you many many examples that say otherwise. https://www.dailymail.co.uk/news/article-524390/The-women-admit--We-just-figure-sums.html https://www.dailymail.co.uk/news/article-524390/The-women-ad... Granted, that same search will show you many examples of content accusing unnamed other people of having this attitude. https://www.science.org/content/article/both-genders-think-women-are-bad-basic-math https://www.science.org/content/article/both-genders-think-w... It’s an antiquated notion in my mind, but I don’t think it is a thing of the past.
- wongarsu 3y ago“women can't do basic math" being an antiquated notion is even weirder. As GP pointed out, companies used to employ lots of predominantly female computers. As a consequence, the first programmers and operators of digital computers were also predominantly women, even if the engineers building them were mostly men. Women being bad at advanced math would make sense as an antiquated notion, but those in charge of hiring decisions until about 50 years ago evidently thought women were great at basic math. The study you linked showing that women lag behind men in math to a degree proportional to some gender disparity metric is also interesting, but doesn't really tell us how we got here.
- kragen 3y agoi think it's (unintentionally) misleading to describe analog 'computers' as 'computers'. what distinguishes digital computers from other digital hardware is that they're turing-complete (if given access to enough memory), and there isn't any similar notion in the analog domain the only reason they have the same name is that they were both originally built to replace people cranking out calculations on mechanical desk calculators, who were also called 'computers' the flight control 'computer' has more in common with an analog synthesizer module than it does with a cray-1, the agc, an arduino, this laptop, or these chargers, which are by comparison almost indistinguishable
- ezconnect 3y agoThey both do the same thing compute an output from given inputs. So they are properly distinguished from each other on how they do the computing. They both deserve the name 'computer'.
- kragen 3y agoonly in the same sense that a machinist's micrometer, an optical telescope, an analog television set, an acoustic guitar, a letterpress printing press, a car's manual transmission, a fountain pen, a nomogram, and a transistor also 'compute an output from given inputs' do you want to call them all 'computers' now?
- justinjlynn 3y agoWhat's wrong with that? They are. We can always make the finer distinction of "Von Neumann architecture inspired digital electronic computer" if you wish to exclude the examples you've given. After all, anything which transforms a particular input to a particular output in a consistent fashion could be considered a computer which implements a particular function. I would say - don't confuse the word's meaning with the object's function and simply choose a context in which a word refers to a particular meaning, adapt to others contexts and translate, and simply deal with the fact that there is no firm division between computer and not-computer out in the word somewhere apart from people and their context-rich communications. If the context in which you're operating with an interlocutor is clear enough for you to jump to a correction of usage ... simply don't; beyond verifying your translation is correct, of course. As you're already doing this - likely without realising it - by taking care in doing so consciously you're likely to find your communications more efficient, congenial, and illuminating than they otherwise would be.
- creatonez 3y agoSome info about the Flight Control Computer: > The Flight Control Computer (FCC) was an entirely analog signal processing device, using relays controlled by the Saturn V Switch Selector Unit to manage internal redundancy and filter bank selection. The FCC contained multiple redundant signal processing paths in a triplex configuration that could switch to a standby channel in the event of a primary channel comparison failure. The flight control computer implemented basic proportional-derivative feedback for thrust vector control during powered flight, and also contained phase plane logic for control of the S-IVB auxiliary propulsion system (APS). > For powered flight, the FCC implemented the control law $ \beta_c = a_0 H_0(s) \theta_e + a_1 H_1(s) \dot{\theta} $ where $ a_0 $ and $ a_1 $ are the proportional and derivative gains, and $ H_0(s) $ are the continuous-time transfer functions of the attitude and attitude rate channel structural bending filters, respectively. In the Saturn V configuration, the gains $ a_0 $ and $ a_1 $ were not scheduled; a discrete gain switch occurred. The Saturn V FCC also implemented an electronic thrust vector cant functionality using a ramp generator that vectored the S-IC engines outboard approximately 2 degrees beginning at 20 seconds following liftoff, in order to mitigate thrust vector misalignment sensitivity. https://ntrs.nasa.gov/api/citations/20200002830/downloads/20200002830.pdf https://ntrs.nasa.gov/api/citations/20200002830/downloads/20...
- dmvdoug 3y agoAnd here[1][2] are a couple of pictures from the Saturn V they have (in the appropriately named Saturn V Hall) at the U.S. Space and Rocket Center in Huntsville, AL. [1] https://imgur.com/qscoWrR https://imgur.com/qscoWrR [2] https://imgur.com/HHg5ohS https://imgur.com/HHg5ohS