I have an idea to complicate matters when playing in an asteroid field.

Extra equipment required: 1D6, scatter die

Procedure: After placing the asteroids and ships, determine direction and speed of asteroid drift. Roll the scatter die. This will be the direction all asteroids move throughout the game. If the scatter die comes up 'bullseye', the asteroids remain stationary throughout the game.

Next, roll the D6 to determine asteroid speed (applies to all asteroids throughout the game). Result of 1-2, asteroid speed = 1. Result of 3-4, speed equals 2 and a result of 5 or 6 indicates a speed of 3.

In the end phase of the turn, move each asteroid the indicated amount using the Range Ruler in the direction indicated on the scatter die. If an asteroid reaches the edge of the playing surface, place it on the table edge directly opposite the spot where it went off the board. Resume it's movement next turn. (think the old old video games like Asteroids).    

 Thoughts?

same as I was thinking, make the asteroids a little less predictable

 I've been working on a set of campaign special rules and this is one. The asteroids are dealt with one by one after the players have placed their movement dials next to the corresponding ships.  A scatter die is rolled for each asteroid and then moved with the "straight 1" template in the direction dictated by the scatter die. 

If there is a collision between an asteroid and ship, I have the owner of the hit ship roll one attack die and determine the results without rolling a defence die.  Immediately afterwards, the asteroid is moved using the "straight 2" template in the opposite direction of the hit ship. This gives the ship, (if it survives) a place to go in the next turn and creates a great randomness that turned out be a great source of comedy and stress in play testing.

Give it a shot and let me know what you guys think.  We've done it four times and enjoyed it, but I'd like more feedback.

If this has been addressed, I apologize.  So when will the asteroids "move"?
I think the asteroids need to move before the ships reveal their maneuvers (Skill 0).  That way you have the "Oh crap!" moment (You think it's a safe flightpath, but you didn't see that coming.).

 You're dead on Steve. The asteroids move, one by one, in between phase 1 and phase 2.  Or a pilot skill level 0 works too. It does indeed create that,  "Oh, I just pooped myself" feeling for the pilots. Pretty fun times.