Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site decwrl.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!gamma!epsilon!zeta!sabre!petrus!bellcore!decvax!decwrl!dec-rhea!dec-tle!crimmin
From: crimmin@tle.DEC (DTN 1-2015)
Newsgroups: net.space
Subject: slingshot effect
Message-ID: <1481@decwrl.UUCP>
Date: Tue, 19-Nov-85 15:00:07 EST
Article-I.D.: decwrl.1481
Posted: Tue Nov 19 15:00:07 1985
Date-Received: Sat, 23-Nov-85 01:56:28 EST
Sender: daemon@decwrl.UUCP
Organization: Digital Equipment Corporation
Lines: 33



> When a spacecraft falls towards a planet but misses it,
> its trajectory is a hyperbola. It leaves with the same
> velocity as it arrived with. BUT note that this is
> relative to the planet! Relative to the Sun, it looks very
> different, and it is possible for the spacecraft to have
> accelerated from zero to twice the orbital speed of the
> planet *relative to the Sun*. 

Queries: 

[Assume a probe using the slingshot effect around Jupiter]

Is the trajectory a hyperbola while the probe is en route
to Jupiter, or only after it misses? 

Watching from Jupiter, the probe approaches and departs at
the same velocity. Does the probe perceive a faster
velocity in relation to Jupiter? to the Sun? 

What is the meaning of *zero* the orbital speed of the 
planet relative to the Sun? Does it mean that the probe
is moving at the same orbital speed as Jupiter? If so, how
does the probe catch up and swing (sling?) around the planet.

Is this correct? From the Sun, the probe appears to 
accelerate to a speed twice that of Jupiter in its orbit 
of the Sun. But from Jupiter, the probe appears to come 
and go at a constant velocity. Can you descibe how this 
works?

Piter (New Hampshire)