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Rocket candy - very interesting. I have linked up the excellent video by the King of Random. 8th promised to email me what the purpose of the iron oxide was in the rocket candy but nothing yet - you get another chance, 8th.
My understanding is that rocket candy combines an oxidizable carbon source
(sugar) with an oxidizer (KNO3). Oxidization produces thrust. I presume that the polymeric nature of the sugar slows the reaction so you get thrust as opposed to an explosion like with powered charcoal and KNO3 (gunpowder).
But sugar already is largely oxidized. Why not use less oxidized carbon? Fats like lard might get runny when the thing heats up and then unoxidized liquified fuel will get blasted out. Wasteful. You could use all-trans fats but thouse might be hard to come by.
Soap has almost as much unoxidized carbon as fat (or alkane) but I here assert will melt less readily - because of ionic attractions? I propose that more powerful backyard rocket fuel could be made with soap. I would use Ivory flakes and mix up the fuel exactly as the King does in the video (together with some rust if 8th is persuasive). My hypothesis is that this will provide more energy per weight than rocket candy.
Looks like they have put some sort of safety on this video so no viewing from work. [bungston, Feb 19 2014]
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||I think you'll find the iron oxide is required in minute quantities, and is used as a catalyst for the decomposoition of the KNO3. It's very very common to have small percentages of metal oxides, or organometals in rocket fuel mixes for this reason - they catalyse decomposition of the oxidiser.
||The difference between solid rocket fuels, and solid explosives, is at times purely in the name. Watch yourself.
||It's a combustion promoter. With propellants
and deflagrants, the combustion front is
propagated by hot particles and thermal
conduction; the rate of propagation being
||At the temperatures involved, iron oxides are
relatively volatile ; iron has the unique
property that its oxide has a lower melting
point than the parent metal, this being the
fact that makes welding it comparatively
easy compared to most other metals.
||Its role is not truly catalytic, as it does
undergo reduction and oxidation reactions. A
true catalyst is unchanged by the process in
which it participates.
||Agreed, but it's normally referred to as a catalyst.
||Then again, I'm fairly sure that it comes out the exhaust as Iron oxide, so it really probably can be referred to as a catalyst.
||Am I getting the role of FeO(x) confused with organometallics in rocket fuels? I had always beleived (because I read it) that organometallics promote the liberation of oxygen in the oxidiser, whatever that might be. I had always presumed that the Iron Oxide did the same thing.