Question about modern subs.

[Oberon]

AFAIK it is possible, after all it's a bit hard to use a periscope to attack a submerged submarine. If the scope is used I think it's usually just for confirmation or intel gathering purposes, and only very briefly since both attack and search scopes can be picked up by surface search radar which is why some scopes have an ESM strength detector in order to warn the user to get the scope down sharp if the readings start going into the red.

Generally speaking though, it's a case of examining a sound output from varying angles to make absolutely sure where it is, then the torpedo will run in with an active seeker, so as long as the enemy contact is within the cone of the active sonar on the torpedo it will acquire and run in to detonate...unless it gets spooked by decoys of course, but if it does fail to detonate and the wire hasn't been cut then you can steer it back in again for a second attempt.

Originally Posted by Jimbuna

The first submarine to be built without a periscope was the USS Virginia built in 2004:



http://www.freerepublic.com/focus/fr/1254706/posts

Astute has the same thing, it is still a periscope that pierces the surface of the water and can be detected (although it is somewhat smaller than the traditional periscope I believe) but rather than run directly from the control room to the surface it is sent to a series of tv screens in the conn (most subs had a secondary TV screen that relayed what the periscope was looking at anyway) so there's penetration of the hull and thus less opportunities for water to get into the people part of the sub.