A quick hint on how to get through the "Ensign Parker" mission:
I spent ALL my torpedos trying to hit the ship, to no avail.
I'm on automatic aiming (I hate trig. and that's what the XO is for anyway!)
to get targeting solutions but I mess with the detonators and speed as required.
If you go to the surface, man the deck gun and SHOOT the #$%% out of Ensign Parker, you pass the mission! (worked for me, anyway). Unloading a few clips of AAA into him is good practice too.
After that it's all plain sailing and you'll be assigned to a patrol base after a couple more walk through missions and then the fun REALLY starts!