Navy coveralls are pretty thin. Submariners (except especially hot watchstanders like engineroom upper level) wear non-uniform sweaters and survival jackets because of how cold it can get due to heat loss to deep cold water. When submarines are in warm water, it’s not nearly as bad.
There is climate control and small heaters, but a submarine is not going to be designed with massive heaters in the HVAC system because it’s a waste of power, space, and a fire hazard. It’s safer and more efficient for people to wear jackets.
Under some conditions, ventilation needs to be secured. There are quite a lot of sources of water in the boat, and humidity and temperature can rise quickly when the fans go off. I remember it being annoyingly uncomfortable to sleep in port and at sea with the fans off.
The green coveralls worn by the guy going into the tube are heavier fabric and only worn when doing heavy cleaning, busting barnacles, painting, etc.
I've read a little bit about life on ships during the age of sail.
One common theme is that the enlisted men's lives are basically thought of much like the wooden planks: Not at all, and if so, only when it's affected the mission, in which case it's beaten back into shape. The sleeping quarters and conditions, the rations, the toilets, etc, all just terrible. Officers had it a smidge better at that time.
Navies are very traditional things. They do things like they always have. Mostly that's because the sea is so dangerous and these methods are tried and tested. But also, that's kinda just the way they are.
So, my null hypothesis is that modern navies, being very traditional, just don't really care all that much about enlisted men.
I would love to be told off here so I can update my priors. If any servicepersons are on HN and would liek to rip me a new one about life aboard a ship, please do!
I've been on modern sailships as well, and also read a bit about 17th and 18th century ships. My impressions are that (excluding galleys) life conditions on board had to be "good enough" and sailors (and soldiers) would openly complain when the small privileges of their category were not upheld, like bigger rations for gunners, alcohol distribution etc.
On a sailship where everything is ruled and organized, you can be okay with very little comfort. Of course modern ships are much better in terms of facilities (the privy's not much different sometimes but there are showers, clean bedding, better food - sometimes - etc), but a hammock with a rug in a room with 20 to 100 other people nearby, above and below must have felt pretty much the same.
There were also vast cultural differences between nations. The Royal Navy was known for the iron discipline and punishments partly because it was very easy to recruit sailors. Nations where Navy service was voluntary, or tied to a social corps were probably different.
Today, in an enduring peace context, there is a great focus on living conditions. Though it has gotten better for enlisted men (notably because automation means more space on a ship for bathrooms, larger rooms with less people etc), some regret the living conditions on older ships with more collective life. 50-men rooms were no strange thing on some big ships in the 2000s, I guess there are still ships like that (I've never been on a ship with a crew bigger than 250). Technology (cameras, alarms, fire detectors etc) also means there is less need for watch duty both at sea and in harbour. I've been sometimes among the ones arguing officers care too much for what the enlisted crew says, especially regarding their "generational need" for social media and hourly Internet access. After a week without smartphones nobody complains about Snapchat anymore.
You're right that there is less concern for enlisted crews. I'd say the points of scrutiny are their psychological well-being (they're often new in this, so more vulnerable to depression, bullying, excesses of various kinds etc), and of course identifying potential and convincing the most talented ones to stay and progress. The reasons for this realtive lack of concern can be:
- They're young, more adventurous and adaptable.
- They have it good: the pay is generous, especially for 18-year-olds (sometimes younger) with little to no qualifications. They have a lot of opportunities, being stationed on the other side of the world, going out in strange places and harbours (except for the US Navy, you have to get two truckloads of Marines to guard the place before you can order a drink at an African bar), and get to learn the job as they progress, especially for the technical ones.
- They can leave very quickly if they want. Petty officers, CPOs and offcers are held by longer contracts, that are often very hard to break unilaterally because of legal provisions specific to the military.
- The focus is on the Petty Officers. Petty Officers have qualifications (highschool, vocational school, sometimes college), and you invest a lot in them. They learn very technical, irreplaceable skills, they manage small teams from a very young age, and you want them to stay and progress. It can take up to 20 years to make a combat management system expert, a military SATCOM specialist. You can't get experienced ones on the job market (cruise missile specialists, ship turbine experts, etc) and you're often unable to compete on salary alone (IT and data specialists, nuclear technicians etc). Not to mention you really need them on the ships...
- There are less and less enlisted crews onboard. The ships are getting more technical, meaning the bulk of the crew is made of petty officers. The US Navy counts POs in the enlisted statistics, so I don't have the exact numbers.
I went as a contractor (fixing a port from PDP 11/44 -> SUN 5/110) on-board a UK nuclear sub back in the 90s, and had a contractor berth in the 'bomb shop'. I slept underneath the Tigerfish MK24 torpedoes, smelly and greasy, but i don't remember it being cold !!
Yes, it can be that hot; I cuddled nude with a TLAM in the Carribbean to stay cool. I think UK boats were built for colder waters; the ventilation couldn't keep up on the deck in the shallow, warm waters.
Things are certainly not made for comfort. In cool waters my blanket wasn't wide enough to protect me from accidentally touching the weapon in my sleep. They're a great heat sink and suck the heat out of you, whether you want it or not.
I'd guess possibly there are times (perhaps many hours at a time) when they have to "run silent" and turn off ventilation fans and heat pumps and keep other mechanical noise to an absolute minimum.
Is it that hot in the submarine that you have to sleep naked and hug torpedoes to stay cool while you sleep? Is there no form of climate control?
On US submarines it must be much cooler as everyone is wearing thick overalls[1] and even winter clothing in the torpedo bay.
[1] https://youtu.be/UYEyhB0AGlw?si=XfZjsJdPCGMBYyhY&t=369