Mike.

This is coolbert:

As it was with the Swedish Vasa from many hundred years ago so was it too only not that long ago now [several decades] with the Soviet K-278 Komsomolets

Soviet submarine, on the FIRST operational patrol SUNK. Caught fire, foundered, sunk, the loss of life not total but still heavy.

"K-278 Komsomolets was the only Project 685 Plavnik . . . also known by its NATO reporting name of "Mike"-class) nuclear-powered attack submarine of the Soviet Navy. The boat sank in 1989 and is currently resting on the floor of the Barents Sea, one mile deep, with its nuclear reactor and two nuclear warheads still on board. The single Project 685 was developed to test technologies for Soviet 4th generation nuclear submarines . . . [it] sank after a fire broke out in the aft engineering compartment on its first operational patrol."

The K-278 a "test bed" as was the Soviet Alfa class submarine. Test new technologies and concepts.  K-278 seems to have formidable capability, awesome even. BUT SANK ON THE FIRST OPERATIONAL PATROL!"

"K-278 had a double hull, the inner one being composed of titanium, which gave her an operating depth far greater than that of the best American submarines . . . Initial Western intelligence estimates of K-278’s speed were based on the assumption that it was powered by a pair of liquid-metal lead-bismuth reactors."

"her [K-278] commanding officer, Captain 1st Rank Yuriy Zelenskiy was honored for diving to a depth of 1020 meters (3,345 feet)."

That the K-278 was able to achieve such a stupendous depth was due to that titanium inner hull? This would seem to be the case. That 1,000 meter depth as a demonstration of prowess the military virtues of such a "stunt" questionable also? The abysmal depths are about 10,000 feet [about 3,000 meters] the modern attack submarine operating at best ONLY in that top tenth of what is normally referred to as mid-oceanic [pelagic] waters!

There is significant advantage to the use of the liquid metal cooled type fast reactor. There are however also disadvantages as you might well imagine. Such reactors were tested with the Soviet Alfa class sub and found to be lacking, theory and concept not agreeing with reality? That reactor design not being ever used in American submersibles and by no one other than the Soviet either.

"They [liquid-metal cooled fast reactors] were significantly lighter than typical water-cooled reactors and had an advantage of being capable to quickly switch between maximum power and minimum noise operation modes"

coolbert.