Is it possible to get a Sun gravity assist?

[Rutabaga22]

This is a weird question, but I was wondering if you could get a sun gravity assist to fling you out to a higher solar orbit you might get if you went from  eve orbit to solar orbit you could get out to jool for a grand tour mission.

[jimmymcgoochie]

No, there's no such thing as a solar gravity assist. To get a gravity assist, you need to fly past another object that's orbiting the same parent body- so if you're in a solar orbit you need to aim for a planet, or if orbiting a planet like Jool then aim for a moon. A gravity assist from Jupiter will fling you right out of the solar system, as it did for the Voyager spacecraft, while gravity assists from the moons of Jool are a great way of capturing into, or escaping from, Jool orbit without needing to use your engines.

Gravity assists work by changing your relative velocity: you enter and leave the planet/moon's gravity well at exactly the same speed thanks to conservation of momentum, but the direction relative to the parent body (i.e. the sun for a planetary gravity assist) is altered. I could try to explain it, but I think I'll let someone who knows what they're talking about do it instead:

[dci]

Simply no, you can not, there is no parent body to change your velocity vector direction.

But what you can, is perform Oberth maneuver close to Sun.