Probably more along the lines of a ship requires X number of crew working 24 hours a day to run properly and the ship can only hold a crew of less than 3X (8 hours shifts, 7 days a week). It's not going to be a simple 9-5 job for everyone on the ship but there should at least be some scientific justification behind whatever shift scheduling the Navy decides on. Do people work better when doing long shifts with long breaks in between or short shifts with short breaks? Can people doing day shifts work longer than people doing night shifts? Do people work better with regular shifts or with ones in different lengths? It's obviously going to be different for every position, anyone making critical decisions shouldn't be overworked but the guy cleaning toilets isn't going to do too much damage being tired. It all boils down to how much can you work someone until it becomes an issue.

Not all crew jobs have to be performed continuously, 24 hours per day.

Obviously, someone has to be in command on the bridge at all times, but it does not have to be the captain the whole time. That's what watch commanders are for, right? The guy cleaning toilets does not need two more guys backing him up for the 2nd and 3rd shift. Dirty toilets wait until he rolls out of his bunk, or until the captain eats a volatile burrito, and someone wakes the toilets guy up to deal with that specific problem outside of regular duty hours.

Command staff already needs to have enough redundancy to operate the ship if an unlucky hit takes out the entire regular command, just as a requirement of being a war vessel. In theory, that Junior 2nd Lt. should be able to limp back in to port after everyone else in the chain of command is killed, so the Navy can send it back out with a fresh crew.

Surely, there's a person whose function is to alert person X when situation Y happens, so that person X is not expected to be awake and alert and staring at green lights for N continuous hours, and then exhausted or asleep when one of them turns red?

> "The guy cleaning toilets does not need two more guys backing him up for the 2nd and 3rd shift. Dirty toilets wait until he rolls out of his bunk, or until the captain eats a volatile burrito, and someone wakes the toilets guy up to deal with that specific problem outside of regular duty hours."

That isn't how it works.

So there are all kinds of functional roles in the Navy (and I'm going off of submarines since that it was my experience was in), roles having to do with operating the sonar equipment, IT/comms equipment, torpedoes, and the engine room. So these people will be on watch (hourly logs, monitoring system conditions, etc.) and then after they are relieved they'll do whatever maintenance and cleaning they are assigned to. There is not a "clean-the-toilets" job role.

I know that's not how it works in practice on a naval vessel, but that's how it works in abstract economics world.

In AEW, specialization rules everything, so the toilets are cleaned only by a specialist toilet cleaner, and specialist toilet cleaners only clean toilets. If you try to shoehorn AEW onto a ship, you only need one toilets guy, because having clean toilets is important, but not so important that it has to be done 24-7.

It is an open question whether it would be more efficient to have 3 radio operators providing 24-7 coverage on the radios during their duty hours and doing other jobs when they are off watch, thus giving them 16-hour workdays divided up into 8-hours of "important" work and 8-hours of "grunt/scut" work, or to have 2 radio operators on watch 12 hours each, and one specialist cleaner taking up that extra 8 hours in that bunk, cleaning toilets 12 hours a day. Is that last 4 hours of work squeezed into the day okay if it requires no dedication or focus?

I too was in subs, the problem here is that you will not always have enough people to man a three section rotation. People cycle on and off the boat very frequently I spent 4 years on the same boat with a crew of on average 160 people. In my time probably 300+ people rotated through, routinely many divisions would have only 2 qualified individuals for a watch station putting them on 12 hour shifts with having to get up in your off time to give a food and bathroom break. The issue is the military goes through periods where a certain rating is undermanned so they encourage the recruiters to take as many people for that rate as possible. Since recruiters have quotas they must fill they take people who are quite frankly useless. Those people end up not able to advance due to several factors and the Navy can only have so many people in a rate at the same pay grade so they either don't let them re-enlist or if they want to stay make them change rates to an under-manned rate. Now not all those who re-enlist will advance due to the same issue so often they just cut there looses and move or they reach higher tenure and can't re-enlist leaving an under-manned rate and the cycle repeats itself.

Most watch stations take months of training to not only get qualified but also for the command to have enough confidence in you to stand the watch. I myself stood a regular 12 hour rotation during times we where on the surface because we had only 2 qualified operators and the rate that actually owned the equipment was undermanned so they could not provide bodies. There are very rarely extra people to do grunt work you do that in your off watch time when you are not studying, qualifying, or doing maintenance. Very frequently commands will care about filling the watch bill over a person not just being qualified but also competent enough to stand a watch, thus accidents happen due to negligence and ineptitude.

When I was in, we had a 6-on 12-off schedule to allow for 24hr coverage with only three watches. Effectively, each of our "days" was an 18hr day, with 6 being on-watch, 6 being used for maintenance/drills/training, and 6 being for sleep. Rarely did we get a full 6hrs of sleep per 18hr "day."

That sounds like the worst possible compromise between 16+8, which gives you a normal "on" work shift and a normal sleep period, and 8+4, which could give you biphasic sleep, or triphasic with 4 hours base sleep and 2 x 2-hour naps.

Even so, it's still 8 hours of sleep per 24 hours, which is adequate, even when only being able to take 6 at a time makes it somehow seem worse. And I have a sneaking suspicion that it only exists because the Navy found that sailors were useless after the 12th hour of working, so decided to set the workday to 12 hours, and just make the whole duty cycle 18 hours. I'm guessing that people on that schedule stop being very effective after just 9 hours of wakefulness. But I'm no somnologist.

The 12-on is composed of a 6-hour operator shift, followed by 6 hours of maintenance and training. I think the 12+6 is based on maintaining full awareness over a 6 hour period, and in that sense it basically works. If you eat when you wake up, and after your operator shift, then that also works out to two meals per 18-hour day, and gives you a normal-ish 12 hour gap between your last meal and waking up.

That is correct. The 6 hour on-watch period is based on maintaining full awareness. With a 3 watch-section crew and "18hr days," you'll have round the clock coverage for all watch stations. Like you said, we'd wake up, eat, go on watch for 6hrs, get relieved by the next watch section, eat, do maintenance/training/etc. for the next 6hrs, and then sleep for the final 3rd of our "day."