From: Michael M. Butler (butler@comp-lib.org)
Date: Fri May 17 2002 - 14:17:28 MDT
"Robert J. Bradbury" wrote:
>
> On Tue, 14 May 2002, spike66 wrote:
>
> > Recall that Isp expressed in newton-seconds per kg.
>
> "Recall"? I doubt that Isp was discussed in my high school
> physics class.
It was discussed in my high school Estes rocketry catalogs. [big :)]
No brag, just fact...
> > Robert do get out of the sloppy habit of using seconds as a unit
> > of specific thrust.
>
> Well, I think I've read either papers from JBIS or perhaps Mallove's
> "The Starflight Handbook" that always used seconds.
>
> Or am I simply mis-remembering things?
Nope, it dates from a long time ago. It is a sloppy habit that I was
taught as a kid, too. The fault may be laid at the feet of people who
weren't using SI and spoke of "pound-seconds per pound".
Problem is, that's pounds-FORCE seconds per pounds-MASS.
Using SI cures one of the illusion that all the units except seconds cancel.
Enough rocket-related stuff still seems to use "Seconds" as a term of art
that it may never completely go away. Sigh.
--
butler a t comp - lib . o r g
I am not here to have an argument. I am here as part of a civilization.
Sometimes I forget.
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