Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!brl-smoke!gwyn 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.