The author doesn’t talk much about the new AIP systems being added to subs.The German fuel cell based systems can go stay under for around 4 weeks at a speed of 5 knots.
5 Knots? That’s really not much to brag about, and you will never ever make a diesel sub as quiet as a nuke, moving parts make noise, and we can hear you when the pistons pump from so far away it will make you sick to think about it.