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Exactly 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
by nothercastle 3y ago
Exactly 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).
- denton-scratch 3y ago
- 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.