every submariner will say that, but they don't know

we need a real war to really answer that question

in my mind, the germans have the best submarine but it can stay underwater for only a week or two

https://en.wikipedia.org/wiki/Type_212_submarine

These boats use fuel cells to make electricity for the propulsion system. Fuel cells don't have any moving parts.

All of our boats are nuclear and with nukes you need to have a coolant pump to keep the reactor running. Coolant pumps make noise. Steam runs the propulsion turbines that turn the shaft thru a set of reduction gears. Steam also is needed to run the electric generators so you have electricity to run all the other equipment on the boat.

Nuclear boats have speed and they can stay at that speed indefinitally. The german boats in their elelement (the Baltic ocean) will rule supreme.

This particular submariner was one of the nuke engineers on the boat. I’m going to give him some credit for knowing what he’s talking about.

Pretty sure we have some submarines in our fleet that can operate at low speeds without a coolant pump running.

The subs today use natural circulation so the electric coolant pumps do not have to run. By this I mean when the reactor core gets the pressurized (2000 PSI or so) water hot it goes up to the steam generator where it makes 500 PSI water into steam and due to heat loss the reactor coolant then goes down to get reheated. The General Electric and early Westinghouse reactors used on the USS Enterprise and all the Cruisers were backwards, with hot water going down? Soooooo in the case of loss of power and no coolant pumps you had to get power back quickly to prevent core over heating!

Twice in the 20 years I spent as a nuclear machinist we lost all power twice on ships I was on and had trouble getting those big diesels started and would watch the core temperature meter like a hawk! At the D1G prototype training site in New York we did a test when core 3 was installed to see if natural circulation was possible.....it was not.
John

how do we combat modern submarines?
 

There's still plenty of other pumps besides the reactor cooling pumps. Maybe the new reactors can have the primary side run on natural convection at low power levels but there are pumps to get condensate from the main condensor back to the steam generators, main sea water pumps to cool the steam coming into the condesor into condensate, trim and drain pumps, auxillary seawater pumps....

I got out in 91 and I'm going off memory. I remember the engine room upper level watch wearing head phones. I'm a bit dubious as to how much submarines have improved in the last 30 years. The basic layout of our boats hasn't really changed. One pressurized water reactor running two turbine electric generators and two turbines running the reduction gears turning one screw. I'll never get a tour of a Virginia class engine room so I don't know whats different about them but I doubt they're any difference, just everything is a little bigger.

You can postulate how much submarines have improved by just looking how big they have grown. The easiest way to make a pump quieter is to make it bigger and have it run slower. And then you make the bends in the piping have bigger radii. This all requires a bigger hull to provide the extra room and more displacement needed.

Anyone can go on wikipedia and look up the progressing submarine classes from the Skate, Skipjack, Permit, Sturgeon, Los Angeles, Seawolf, Virginia and see how they've grown.

The newest Japanese boats are still diesel electric but they're using modern batteries with a lot better energy density compared to the old lead acid technology of our last diesel electric boats built in the 50s.

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Nuclear combat! Toe to toe!

Interesting backstory on the safety elements of that warhead. Enough so that I have a widget or two from that one, and one of its near relatives, on my desk - they're worthy of a look for our engineers today even if they are nearly 60 years old.

The info about all the other pumps besides reactor cooling pumps is pretty much true and most of those are run 98% of the time. Only on "silent running are all mechanical things shut down or turned off and in that case only the electric motor and it's shaft connected to the propeller running. Even the prop is shaped so there is no noise from cavitation or water noise. That is why in pictures of our subs in dry dock show a cover over the prop and in some cases are guarded. Surface ships also cover their sonar dome on the bow of the hull so it can't be seen?

One of the Spruance class destroyers hit a whale off the coast of Australia and put a long gash in their sonar dome. They limped back to San Diego, were put in the dry dock and a replacement dome sent by C5 Galaxy from the east coast. It landed at NAS North Island and immediately ran into a HUGE problem......seems the rubber/cloth/sealer the dome is made of is poison so those pesky sea creatures will not grow in it! Well San Diego would not give permission to cross the bridge, so the state gave permission to truck it down the "strand", through Imperial Beach the up interstate 5 to Naval Station San Diego with the roads all being shut down and then checked to insure no contamination had occurred. The old dome was removed inside a huge tent and all the workers had security clearances and wore protective suits. Total cost in 1986 was about 6 million dollars give or take a little. I was one of the two SupShip QA people assigned to insure NASSCO did the job correctly.
John

That’s an interesting story, thanks. Never fails to amaze me how elected bureaucrats can make really stupid ****ing decisions. I guess half the country was born without a lick of common sense.

I’m too claustrophobic in my old age to “enjoy” living on a submarine but I sure am impressed with our submarine service.