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From: desj@brahms (David desJardins)
Newsgroups: sci.space
Subject: Re: Specific Impulse
Message-ID: <14@cartan.Berkeley.EDU>
Date: Tue, 14-Oct-86 17:55:06 EDT
Article-I.D.: cartan.14
Posted: Tue Oct 14 17:55:06 1986
Date-Received: Thu, 16-Oct-86 08:23:24 EDT
References: <8610131130.AA10458@s1-b.arpa> <748@hplabsc.UUCP>
Sender: daemon@cartan.Berkeley.EDU
Reply-To: desj@brahms (David desJardins)
Organization: Math Dept. UC Berkeley
Lines: 20

In article <748@hplabsc.UUCP> dsmith@hplabsc.UUCP (David Smith) writes:
>> 
>> I   = m V   / m g     =  V     /  g
>>  sp      e        o         e       o
>
>But why is it defined with that silly g-naught in the denominator?
>(all together now!)
>
>	    TO JUSTIFY MEASURING IT IN SECONDS!

   David Smith is clearly right.  The *only* possible justification for
introducing a factor of g0 -- a completely arbitrary constant from the
point of view of, say, a lunar lander! -- is to make things simpler for
those who use the English system and don't know enough to distinguish
between pounds and pounds-mass (or slugs).
   That it has always been done that way is no excuse.  The misunder-
standings of the past are no justification for continuing a source of
confusion in the future.

   -- David desJardins