alt Hacker News> Conversely, entire branches of knowledge can be lost if not enough people are working in the area to maintain a common ground of understanding.
Especially if the work is classified.
The manufacture of FOGBANK, a key material for a thermonuclear weapon's interstage, was lost by 2000 because so few people were involved with its manufacture and the ones who knew retired or moved on. It's thought to be an aerogel-like substance.
5 years and millions in expensive reverse engineering was required to figure it out again.
I'm guessing they documented it this time.
My favorite part about the FOGBANK story is that once they figured out how to manufacture it again, the new version of the material was more chemically pure than the old version, but this actually made the material LESS effective, so they had to add spcific impruities back into it to make it work correctly.
[0] https://www.twz.com/32867/fogbank-is-mysterious-material-use...