Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Equatorial Launches
Message-ID: <1991May17.021936.17632@zoo.toronto.edu>
Date: Fri, 17 May 1991 02:19:36 GMT
References: <22727@shlump.lkg.dec.com>
Organization: U of Toronto Zoology

In article <22727@shlump.lkg.dec.com> kendrix_j@mims.enet.dec.com (John R. Kendrix) writes:
>I've seen a few posts which have mentioned in passing that NASA derives some
>benifit from launching close to the equator ...
>I understand that there is centrifugal force involed with the earths rotation,
>but I don't see how that can act as a booster to help the shuttle get into
>orbit. 

Centrifugal force is what keeps spacecraft in orbit.  [Pedantic Physics 101
students wanting to quibble about whether this is a real force should study
some general relativity before making pronouncements on the subject.]  Nature
does not care whether the velocity needed to get into orbit comes from rocket
boost or from Earth's spin.  If you launch due east from the equator, you
already have about 500m/s out of the 8000m/s or so of eastward velocity you
need to get into orbit.  Another way of putting this is that Earth's equator
is already about 1/16 of the way to orbital velocity.  That may not sound
like a lot, but it's enough to make a noticeable difference in payload.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry