Had an, "oh, that's how" moment - Slingshot manuever So I've pondered on this off and on, could never see how it was possible, suddenly it just hit me.. tell me if I'm correct. In order to gain speed the object is using the orbital (or simply directional) trajectory of another. It allows itself to be pulled/tugged/towed towards, ideally on the same trajectory as the object, siphoning off it's momentum into itself for a boost. I'm assuming the ejection trajectory must be quite steeper than the insertion in order maintain this momentum, taking advantage of the exponential drop off of gravitational pull over distance. Makes sense to me, but did I get it right? Thanks! I can also see how coming in the opposite direction could also work as well, by not doing the math though I'm not sure which would produce a better result. Sorry, also just realized this probably belongs in the Classical Physics thread. Don't know how to move/delete this original post.