For those who don't know what a gravity boost is, here is the simple picture.
In the reference frame of the planet you will travel in a hyperbola as you go by. The incoming branch is from the front of the planet, the outgoing branch is also in the front of the planet. So you go from moving backwards to moving forwards.
However the planet is moving in the reference frame of the Sun. The initial "moving backwards" is actually more like "sitting there". The ending "moving forwards" is actually something like, "moving up to 2x as fast as the planet".
So a gravity boost only looks like a gravity boost in a reference frame that is moving relative to the object. Furthermore the gravity boost also does nothing to help you to escape from the object you're getting the gravity boost from.
Therefore we cannot get a gravity boost from the Sun to leave the Solar System. And a gravity boost from the Sun does not look like a gravity boost to us, in orbit around the Sun.
In the reference frame of the planet you will travel in a hyperbola as you go by. The incoming branch is from the front of the planet, the outgoing branch is also in the front of the planet. So you go from moving backwards to moving forwards.
However the planet is moving in the reference frame of the Sun. The initial "moving backwards" is actually more like "sitting there". The ending "moving forwards" is actually something like, "moving up to 2x as fast as the planet".
So a gravity boost only looks like a gravity boost in a reference frame that is moving relative to the object. Furthermore the gravity boost also does nothing to help you to escape from the object you're getting the gravity boost from.
Therefore we cannot get a gravity boost from the Sun to leave the Solar System. And a gravity boost from the Sun does not look like a gravity boost to us, in orbit around the Sun.