I ran the nuclear power plant on the USS La Jolla (SSN-701) for five years. Per the Engineering Department Organization Manual, you're not allowed to do any operations in the power plant if you haven't gotten a certain number of hours of sleep in the past however many hours. This is the most laughably ignored rule on the ship. It's very normal to have people operating the power plant after being awake for 40 hours straight. (I still remember getting yelled at for falling asleep during training because I'd been awake for >24 hours, and the training was about the importance of being well rested and how the Department of Transportation developed its sleep requirements by studying railroad operations. Maximum irony.) Naval Reactors, the organization that supervises the whole navy nuclear program, knows this is the norm and helps hide it. I remember, during the briefing prior to every reactor startup, the engineering officer would say loud and proud "If you don't think you can perform your duties for whatever reason, any reason at all, if you're too tired, raise your hand." One time I had been awake for more than a day straight and I was suicidal, I had been scheduled for 12 hours on watch, 6 hours off watch for several days, so I said fuck it, and I raised my hand. "Per the EDOM, I am not allowed to stand watch because I've been awake for far too long." The engineer recommended me for Non-Judicial Punishment for 1) not being ready to stand watch and 2) having stood watch previously already too sleep deprived to stand watch. I wasn't actually punished because I threatened to call the DoD Inspector General. The whole system is rotten as fuck.