I wonder if it would be easier if there was a laser aiming line instead, so that you know which way the ship is pointing, or if the ship was longer, so you can tell which way it is pointing more easily. The ship is too round, making it more difficult to tell where it is facing.
Right now, a cursor makes sense because the ship is trying to point to where the mouse cursor would be, but removing that link would remove the need for a cursor. One way to make it more challenging without having a cursor, is to remove the mouse controls for aiming. Instead, use space bar for the fire button, and up/down to manually rotate the ship's aim clockwise/counterclockwise. Keep left and right for the orbit (as it is). Then have a little semi-transparent line extend from the front of the ship so you can see what direction it is aiming.