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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: sci.math,sci.misc
Subject: Re: Rockets
Message-ID: <6791@brl-smoke.ARPA>
Date: Fri, 4-Dec-87 13:38:09 EST
Article-I.D.: brl-smok.6791
Posted: Fri Dec  4 13:38:09 1987
Date-Received: Wed, 9-Dec-87 04:26:25 EST
References: <349@xroads.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) )
Followup-To: sci.misc,sci.physics
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 34
Keywords: Engine design
Xref: mnetor sci.math:2537 sci.misc:660

In article <349@xroads.UUCP> wiz@xroads.UUCP (Mike Carter) writes:
>... (1) Gas Law math
>made easy (I see you're laughing) (2) Better equations for nozzle design.
>(3) Composite solid propellant formulas (we have 3, they are inefficient
>and experimentation isn't our bag).

Rocket motor design is a big subject.  I remember finding a book
"Guided Missile Engineering" by Ramo (the "R" in TRW) helpful.
I suspect by now there are better references.

As to the fuel, a really good one is likely to be dangerous too.
Ammonium perchlorate, aluminum dust, and some organic fuel such
as rubber are the ingredients of motors like the Shuttle's SRBs.
The fuel has to be cured, and cracks in it can cause a motor to
explode.  You're probably better off using lower specific impulse
formulations such as the old standby potassium nitrate and sugar
(melted in a double boiler, and cast in place around a waxed rod
to leave a hollow core when the rod is removed).  This is still
dangerous, but less so than some formulations.  I don't recall
the best proportions for sure, but I think it was 3:2 by weight.

Some amateurs used to use zinc and sulfur, but I never had much
luck with that.  Commercial model rocket motors, at least the
earlier ones, used highly compressed DuPont FFFFG black powder.

You will also need a good igniter (it should spread flame down
the whole core), and some fuels won't burn unless the pressure
is high enough, which can make ignition more difficult.
(Potassium nitrate/sugar burns okay at 1 atm.)  

Please be careful; any kids reading this should obtain adult
supervision before working with potential explosives.  The
adults may be uncool, but they've learned how to be cautious
over the years.