What dictates the direction of the spawn?
In my previous game they ended up just wandering in one general direction then making a U turn at a junction planet and heading the other way?
And by the way, I think the engine health of the dyson spawn should be infinite. It requires a lot of micro and attention to get the spawn to move. I say this as once the spawn make their way onto a planet with an ion cannon on it, they all get stuck close to the wormhole as the ion cannon has disabled their engines.
And as a side note, is the engine damage on the ion cannon really necessary? Seems it's just there to make it more annoying when you attack with ships out of it's instakill range?