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The 555 timer is considered the most famous integrated circuit of all time and is also credited with a versatile use in space travel. Hans R. Camenzind (the designer of the 555 timer) said that this IC is used for spacecrafts. However, I can't find more on this. Therefore the question, what is the 555 timer used for in space travel?

Amor
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    I'm not familiar with any space use of the 555 but if it was, it would have to be post-Apollo since the 555 wasn't introduced until 1972. That would be long after all the Apollo electronics had been designed and built. It may have been used in Space Shuttle program or possibly in one of the many satellite designs. But without a specific reference from the place you found that quote, it's anyone's guess. – jwh20 Mar 13 '21 at 14:40
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    In the '80 the 555 was the monostable of choice for IC reset signals. But even if it was for blinking a warning light it would have been useful – Lorenzo Marcantonio Mar 13 '21 at 17:14
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    Hmm I don't know about opinion based. Maybe it is as it's a general application question. 555s have reliability advantages, not-awesome but not-horrible precision and accuracy, great versatility, higher voltage tolerance than many more modern replacements, larger package size than modern replacements, but smaller package size than individual components. Greater simplicity means larger circuits on the same size die and fewer potential failure points, external passives are accessible. Single unit size allows for redundancy. Where would *you* use it in space? – K H Mar 14 '21 at 03:38
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    The reason I ask is this sounds like a school related discussion question, which means you should show us some effort, even if it is on topic for other reasons(which I'm not sure of). One thing I've heard many times aside from the advantage of using components with more years of proven reliability is that more primitive chips are easier to radiation harden(which *still* costs a mint) in the first place as smaller structures with smaller currents and voltages are more susceptible. – K H Mar 14 '21 at 03:45

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It's used for the same sort of stuff you'd use it for on the ground. As a timer, as an oscillator, for pulse generation, as a watchdog timer... you have many of the same needs aboard a spacecraft as in any other type of electronic system.

For most space missions, designers will specify uprated, space-qualified versions of standard parts. TI sells one such variant for the 555 timer, the SE555 which is classified as QML V (ie: suitable for space): https://www.ti.com/product/SE555-SP.

You certainly pay a premium for space-qualified components, though: TI lists the SE555 as $165 each in quantities of 100, which is quite a price delta when you consider a jellybean 555 goes for less than $0.10 in similar quantity.

This price difference is one of the reasons that low-cost space missions such as CubeSats and SmallSats use commercial or automotive components instead of space-qualified ones. The relability is lower, but the mission cost constraints prevail.

The other reason is usually part availability: as a rule of thumb, radiation tolerant space qualified components lag 10-20 years behind the current state of the art. Many of the missions enabled by small satellites are only possible due to the small size and high level of integration afforded by cutting-edge microelectronics. So, they accept the risk of using new commercial components as it would be very difficult to build a mission in that mission class limited solely to a selection of (largely dated) space-grade parts.

Synchrondyne
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