Homing projectile spiral motion, How to?

Sounds like this could work! Thanks, I assume there is a way to find out the target distance without resorting to traces. Perhaps by a node that could figure out how close the target is to the projectile? This way we can have the diameter of the spiral narrow down to its original center position the closer it gets to the hit target and wider the further away it is from the target to give a nice effect.