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Comment by geenew | Hacker News Reader

I once encountered a situation with a very expensive field laser. At one point, measurements started showing an increasing amount of offset.

Over a period of days, the error became increasingly, comically bad, until finally the system refused to boot.

A technician was called, and after hearing about the behaviour, the first request was that a photo of the laser light exit port be taken.

It was obvious why it wouldn’t boot: a mirror in the light path had fallen off.

The worst part was, the mirror had been held on by glue, and had been slowly slipping out of place. The hot climate was probably a factor.

They really should have had someone to say ‘you can’t ship that’ when the topic of glue to hold mirrors came up.

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This exact problem happened with an optic in my lab in graduate school. For two years the senior grad student and postdoc blamed each other over the entire apparatus becoming misaligned every couple of days. (It was a really toxic environment.) Eventually, they both left, I was the only one there, and it still became misaligned. In one day I tracked it down to a prism from Thorlabs whose glue had gone bad positioned at the very beginning of the laser line- it was sliding in its mount.

I wish I had pushed more strongly about it. We spent probably a full person-day of work every week on that.

Oh man, this one hurts to read a little bit. It's crazy how people cooperating poorly can eat up that much working effort.

Reminds me of that giant pager outage ~ 20 years back. I remember one of the stories mentioned a woman who was going to leave her husband because he wasn't answering her page.

Well that's just abusive, really (to threaten to leave someone for not being in minute by minute contact with them/clear signs of an abuser power tripping).

Later in my career, I worked for a company whose principal technical strength was that they knew how to glue optics together in such a way that they NEVER moved, either thermally, or from shock. Detachment? The optic would break in an area besides the glue joint first. And the solution had little to do with the nature of which glue, which however was also optimized. These assemblies were flown in space, landed on the moon, and were in all U.S attack helicopters.

>They really should have had someone to say ‘you can’t ship that’ when the topic of glue to hold mirrors came up.

I work in product at a hardware company and have a lot of domain experience which came from spending years in the (literal) field. There's been many times where I write a product spec and the engineers are incredulous. "Really? It gets THAT hot?" or "Do we really need to provide a bonding/grounding lug on the case?"

It's not uncommon to find engineering teams with deep domain experience in one area, but completely lacking in others. Ignoring domain experience, there should have been rigorous product testing during design that would have weeded out the glue issue.

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