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From: aae391aa@uxh.cso.uiuc.edu
Newsgroups: sci.space.shuttle
Subject: Re: Galileo Gravity Boost
Message-ID: <34700003@uxh.cso.uiuc.edu>
Date: 20 Oct 89 09:41:56 GMT
References: <12027@eerie.acsu.Buffalo.EDU>
Lines: 17
Nf-ID: #R:eerie.acsu.Buffalo.EDU:12027:uxh.cso.uiuc.edu:34700003:000:799
Nf-From: uxh.cso.uiuc.edu!aae391aa    Oct 20 00:35:00 1989


4:00 pm  Oct 19, 1989, stein-c@acsu.Buffalo.EDU writes:

 > Can anyone explain how Galileo will be gaining energy by flying near
 > planets? I understand that the spacecraft will be gaining velocity due
 > to gravity forces as it approaches Venus, etc., but wouldn't all of that
 > energy be lost as Galileo goes away from the planet and has to go
 > against gravity forces? The only way I can see it is if Galileo picks up
 > some of the energy from the velocity of the planet. 

The spacecraft does not get a boost in its speed (it speeds up approaching a
planet, e.g. Venus, but slows back down leaving), but rather a change in its
direction of motion as it sling-shots around Venus, and thus a change in the
orbital trajectory about the sun.

					Erik A. Johnson
					johnsone@uxh.cso.uiuc.edu