[meteorite-list] Gravitational slingshot

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu, 18 Jan 2007 15:06:57 -0800
Message-ID: <A8044CCD89B24B458AE36254DCA2BD0702D3BCBB_at_0005-its-exmp01.us.saic.com>

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
Received on Thu 18 Jan 2007 06:06:57 PM PST