Originally Posted by dcb

Any vessel you put in a mission will start at the defined speed, but will eventually slow down to zero if you don't define also a speed for the waypoint. New waypoints are always set with zero speed and you must change the speed by hand (right click on waypoint).
Now, coming to the unmanned sub, it depends on what version of AI sub you are using. They come in several "flavors", with or without crew set on deck. A version with crew on deck has been created by Sergbuto and you can find it here:

http://hem.bredband.net/serbut/

I've done my own experiments with AI subs/ships and I think you'll find them very limited in what they can do, actually frustratingly limited. Apart from attacking the enemy when in range, they can do nothing. They strictly stick to their set waypoint and are unable to go after the enemy on their own. In fact, the only ship AI worth of this name in the game is that of escorts. They move on their own when they see the enemy, they attack realistically etc. All other vessels are most limited. Even big warships like battleships or cruisers are limited to this "follow the waypoints" behavior.
Further reading about AI subs and wolfpacks here:

http://www.subsim.com/radioroom/show...pack+crew+deck