Strike Suit Zero

Set the game mode to easy. Select the bomber as your ship.
For the first part, just avoid all the fighters, hang around and wait.

For the second part, just spam your torpedoes as you approach the first ship. You should kill it by the time you reach it.
Repeat the spamming of torpedoes for the next frigate.

For the cruiser, i just sat back behind the engine and spammed from there. It couldn't attack me.

You should be able to finish it before the fighters come and help.