Thank you Art. I've been reading about sling-shot maneuvers for decades but never grasped that fine distinction. Very nice.neufer wrote:... It's like a spacecraft doing a flyby of the planet Jupiter:
1) So far as Jupiter is concerned the spacecraft exits with exactly the same speed |Vx| as it entered with |Ve|.
2) However, since Jupiter is moving with velocity vector VJ vis-a-vis the solar system the dynamical exit speed |Vx+VJ| does not necessarily equal the entrance speed |Ve+VJ|. This fact has been used extensively to boast the speed of all spacecraft passing beyond Jupiter (by intentionally flying behind Jupiter).
The things you don't know you don't know!
Rob