Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!ames!pasteur!cory.Berkeley.EDU!navas
From: navas@cory.Berkeley.EDU (David C. Navas)
Newsgroups: sci.space.shuttle
Subject: Re: Galileo Gravity Boost
Message-ID: <18630@pasteur.Berkeley.EDU>
Date: 21 Oct 89 04:47:30 GMT
References: <12027@eerie.acsu.Buffalo.EDU> <34700003@uxh.cso.uiuc.edu>
Sender: news@pasteur.Berkeley.EDU
Reply-To: navas@cory.Berkeley.EDU.UUCP (David C. Navas)
Organization: University of California, Berkeley
Lines: 25

In article <34700003@uxh.cso.uiuc.edu> aae391aa@uxh.cso.uiuc.edu writes:
>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
[deleted]
>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.

No, that's true, but it's not.  I mean -- it *does* get a change in its speed
(think, relative to something else -- relativity's a tricky thing where there's
little to be relative to...).  It also gets a change in direction.  Otherwise
the darn thing would have to [bounce] off the surface of a planet.  Not a
<good> thing... :)

Think of it this way.  get one of those big 'ole super-bouncing rubber ball
things.  Throw it at a stationary car.  ooo, look how it bounces back.  Now
throw it while the car's moving toward you at 60 mph.  Get the picture??
[Oh, and duck real fast :)]

It's a simple, if not exactly accurate, description.  I always went for simple,
myself :) [That was a disclaimer, folks]
David Navas
navas@cory.berkeley.edu