No, the amount of speed you gain (delta-v) is, at an ideal condition, twice the orbital velocity of the planet (or moon) you're flying by. (Imagine throwing a

No, the amount of speed you gain (delta-v) is, at an ideal condition, twice the orbital velocity of the planet (or moon) you're flying by. (Imagine throwing a ping-pong ball at a truck. If the truck is at rest, you get the same speed back. If the truck is running at 60 mph, you may go to jail, but assuming you don't, you get back a 120 mph ping-pong ball.) A planet that far away from the sun must be moving at a very slow speed (otherwise it will escape the solar system altogether), so you can't gain much speed flying by.