Talk:General Discussion/@comment-24903916-20140906180613/@comment-139.193.100.136-20140907015700

Ameno, google "Indian Navy collision" and "US Navy collision" and you'll find out that collisions happen a lot even with modern navies equipped with gee-whiz navigation and sensory equipment. In the past 5 years both Indian and US Navies have experienced a few collisions that mirror the IJN's. The reasons for those collisions are also similar.

The majority of historical IJN collisions before WW2 were basically parking accidents. They happened to smaller ships in crowded ports or anchorages. The underlying cause was Japanese colonial expansion in this period. Ship numbers were growing. Newer and bigger IJN ships were often forced to operate in underdeveloped areas without the proper infrastructure to support them, a situation exacerbated when Japan pulled out of the First London Naval Treaty. In many cases, the policy was to order smaller ships to park at their own power due to the lack of tugs. Since smaller ships in this case actually meant thousand-plus-ton-displacement DDs, collisions were inevitable.

The mechanics of pre-WW2 ships also contributed to this problem. Civilians today are used to ships that can be stopped AT WILL, but this is made possible by two technologies available today: The azipod (a propeller housed in an independently-moving podded enclosure) and the modern naval engine (diesel or gas turbine) which functions similarly to the engine in your car (if diesel) or a modern aircraft (if turbine). WW2 warships were powered with STEAM turbines. Unlike diesels and gas turbines, steam turbines have ramp up and ramp down times, which means their power cannot be instantly throttled. The gearbox for a steam turbine is a bit more complex than that for gas turbines or diesels because it must account for that ramping before it could transfer power to the propellers. This is the cause of inertial collisions as described by Evilfrank in his post. In the time it took for a steam turbine's gearbox to reverse propeller turn to brake, many things could happen because the ship would have been moving under inertia and basically impossible to stop. Modern warships can actually brake and reverse in seconds, but a WW2 warship may need a few dozen seconds to half a minute to even start braking.