Past 10 years in my job, never seen one silent diesel engine. They run pretty noisy on submarines too.
Yet we have got a lovely bulkhead (well - isolated) that keeps it away from operations center.
Despite of having maximimum speeds over 20 knots, lead-acid batteries generate toxic gases when heavily loaded and tends to warm up beyond how it can be cooled. I am sure it can run more than several hours at maximum speed (theoretically considering the battery capacity only) but the battery temperature and aforementioned gases wouldn't let it happen.
Been lucky to dive with a submarine before and after MLU, and lastly with one Reis during trials. And i came to this conclusion; the real mastery of diesel-electric submarines come with the PMM (Synchronous motor) and double-platform isolators. AIP, Li-Ion, Lead-acid introduces a little 'bump' there. AIP indeed gives a one-time shot skipping few snorkels and gives an upper hand but it is not enough alone.
While with Preveze and Gür Class Modernizations we are taking these submarines to what Reis Class have, in terms of electronics, sensors, integration of weapon - network systems, the difference of motors and double platform are absolute.
Possibly these two techs will be the bottleneck at Milden programme, i have no doubts on that AIP and Li-Ion can be achieved sooner than PMM double-isolating platforms.
