They would need all kinds of license's and regular inspection from the BATFE and shit.
I was interested in doing some hobby and research chemistry sorta like a combination of the precision projects I see from
https://www.youtube.com/channel/UC8i-4EpLBXMzekETNXwcZjA
https://www.youtube.com/channel/UC06HVrkOL33D5lLnCPjr6NQ
And more focused on the energetics stuff combines with just technology and research.
Well I did some digging and the ATF is regulated the industry to hell and back. And while I can recognise the importance of safety, I think that it also creates more additional barriers to entry. Especially considering this would a been a weekend hobby if it would have been possible.
TLDR: a lot of people talk about the logistics or the funds to start doing something like artillery production or silicon chip fabrication....and yes I agree but I think the regulation of everything has created so many barriers....you can't experiment in the backyard like you could in the 90's.
Were the 90's safe? No. But we also didn't know the real risks back then when it came to certain chemicals. Also, the growing population makes it more and more hard to have land where you can safely do things....in the north east coast its hard to find and long gun ranges, some states basically banned all the good fireworks, and all this regulation means having just more and more money to figure out how to navigate this issue....which means its not a hobby but a job.
I see plenty of cool things on YouTube from chemistry to engineering and part of me is not sure if the feds are just ignoring what these people do....because it dosnt seem legal, or if they are just lucky that they live somewhere with loosed regulations.