[meteorite-list] Gravitational slingshot

[Matson, Robert]

Hi Rob,

> Could someone clarify something which ahs been bothering me for
> years about this gravity assist technique?  Why does the spacecraft
> come out of the gravity well going faster than it went in without
> thrust?

The trick is that you have to keep track of your reference frames.
You are quite correct that the ~speed~ relative to Jupiter will be
the same pre-encounter and post-encounter (though not the direction),
but Jupiter is not stationary w.r.t. the sun, and as a consequence
the velocity of the spacecraft relative to the sun can change quite
a bit -- up to twice the orbital speed of Jupiter in this case.
(Jupiter's orbital speed is > 13 km/sec).

--Rob