Sciencemadness Discussion Board

Exotic solid rocket propellants

nn2001 - 6-11-2018 at 10:12

Hello sciencemadness community.

It is my first post here, please don't judge me because of my formatting. ;)

I have seen the High-energy propellants on Wikipedia. They use the standard APCP with some energetic fuels (RDX, HMX). So my first question is, why these Nitramines? What does make them so suitable? I have never burnt them myself, but I saw RDX burning on YouTube.

There are also other special propellants (see Patent) like Petrin acrylate. I first saw this compound on the controversial chemlab and now I found a patent for the synthesis of it. But this patent uses Phosgene, this makes this synth unsuitable for me. :(
I would like to see this combusting, so if anyone has made it, could you please tell me what it is like?

And also I have recently obtained 5-ATz. I tried burning some and it looks really nice (like NG), a large not very hot white flame -> see vid (sorry for the low quality). On this forum I have seen someone calculating an energy of it (sry I forgot what energy and who posted it) and it seemed to outperform RDX quite a bit. since there is so much nitrogen in this molecule, would this make a very good propellant?
In the future I want to make the nitrate salt of it to improve the oxygen balance (I don't know nothing about the thermal stability of it, feel free to inform me ;) ) with that thought, I want to reduce the ammount of AP used in the propellant (because of irritating HCl fumes).

I will need to conduct some tests in the future, but sadly I cannot get hold of HTPB rubber. I thought of epoxy resin or silicone rubber (sealant or for molds)

Thanks :)

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DubaiAmateurRocketry - 6-11-2018 at 14:30

You can completely replace AP potentially.

First using a perchlorate-free energetic oxdizier (eg. ammonium dinitramide), followed with a binder that isnt extremely oxygen negative like HTPB. Polyethylene glycol, polytetrahydrofuran could work.

Such a combination (ADN + PTHF) could perform better than APCP by at least 10-15 seconds in terms of Isp

[Edited on 6-11-2018 by DubaiAmateurRocketry]

nn2001 - 7-11-2018 at 07:40

Thanks for the reply.

Regarding ammonium dinitramide, I have been interested in its synthesis for quite a while, but I had to put it on my "long list" firstly because of the extremely low temperature (I have worked with dry ice before, but I would think it is rather difficult because the yield dramatically decreases if you are 10° off...). And the route via potassium dinitramide seems easier (I don't want to work with gaseous ammonia). Someone on this forum said that KDN burns with sugar like KClO3 :)

I also have quite a bit of AP on hand, maybe I will try to stretch my primary fuel or oxydizer (like the cheap cocaine with baking soda :D)

Polyethylene glycol is a great suggestion because of its OB, thanks!
I don't know how to prepare an propellant with Polyethylene glycol... Maybe using a mix of an higher molecular weight one and the other rather a low one. The higher ones are solid and the lower ones are liquid -> do they dissolve in each other like Gelignite? I have prepared my Gelignite a different way, by dissolving NC and adding NG to it and let the solvent evaporate, maybe that's a way to process it?

Are there any known polymers I can make out of 5-ATz?

Paraformaldehyde would also be of interest because of its OB, but it fumes and I don't want to breathe in formaldehyde fumes;)

There seems to be a yellow crud when 5-ATz combusts, any idea what it is?

Microtek - 13-11-2018 at 08:25

Silicone works well as a binder in combination with ammonium nitrate and a metallic fuel. This propellant can of course also be modified by the addition of energetics like RDX, NG/NC, etc.
5-ATz-nitrate is quite stable, but it is also a very powerful explosive (comparable with HMX, IIRC). You should take appropriate precautions.
According to (the abstracts of) a number of papers, poly(acrylonitrile) can be functionalized with 5-ATz groups by reacting with sodium azide and ammonium chloride. I don't know of a way to form a polymer from 5-ATz itself.

I would think that there is a possibility of using uncured viton rubber as the binder, to take advantage of the high energy of the C-F bonds relative to Al-F bonds. However, UNCURED viton is not easy to obtain, and Viton that is already cured is not soluble in anything that could be used to prepare a propellant.

MineMan - 18-12-2018 at 00:10

I saw a document online a year ago... it may of been taken off because in all honesty it never should have been online...

It was about next generation tank propellant. The simple gist of it I believe was to essentially (it’s been long enough that my own ideas have blended into what I think I read, but I will try to keep it as factual as possible) to create a much larger pressure impulse, through, the mirror ignition using an electrical arc in the center of the shell, and of course alane. These two changes led to significant increases in velocity. I.E. over 5000fps from 3200fps. If someone could find that document.

I am of the belief that we have the means, we just don’t do a good job or job at all of taking laboratory tests to the field. Metal hydrides should be huge, the high heat of formation of metal oxides plus the low molecular weight of H2!

According to this document, 600isp is achievable with boron!

I had only previously read slight improvements with the addition of beryllium or alane such as 15-40isp, so the above was a shocker.

I think the ideal would not be a SSTO, but rather a two stage. Stage one, air breathing, stage two densest possible fuel and oxidizer. I reckon if I had the materials on hand, the highest volumetric density propellant would be a mixture of Lithium Perchlorate ( or why not lithium dinitramide), FEP, and boron and or beryllium hydride.

The FEP is crucial, one the flourene prevents the pesky, sticky gooey, and all together aweful liquid boron oxide from protecting the un reacted boron, second, flourene and lithium is highly energetic, that way the lithium from the Perchlorate is not wasted... we may not even need much boron. The density should be around 2.5...

nn2001 - 8-1-2019 at 13:22

Thank you very much for your responses.

As for the Aminotetrazole, I have read somewhere that this could be initiated by a laser to generate gases, as a kind of composite of course :)

This whole idea with alane as a fuel is a bit tricky for me. I looked around and found no supplier of it. There were quite a few listings of Lithium aluminum hydride btw. I thought of using it as fuel, because the decomposition products of it may be of interest. These are lithium hydride, aluminum and hydrogen gas. Lithium hydride further decomposes at 600 deg C into Lithium and hydrogen, thus generating an alloy composed of lithium and aluminum. This special alloy is used in aerospace and was also investigated as a fuel for APCP (IIRC by Purdue on YT). Lithium is quite nice because it is a light and active metal tamed in lithium aluminum hydride. The formed hydrogen is also quite good and the aluminum is used since last century as a cheap fuel. The downside of the whole story is that LiAlH seems to be quite expensive for a primary fuel along with the binder (CIF about 400$). Maybe it could be used as a secondary stage of a rocket or even a tertiary.
Boron seems to be nice, but because of the price, I would rather use it in the upper stages.
What about sodium azide? Great gas evolution and a highly reactive metas as a biproduct... (I am not a rocket engineer but this sounds good for me:D)
Would an addition of cerium ammonium nitrate increase the performance? Should be a powerful oxidizer, non- to minimal hygroscopic and readily available.

As for the binders, why did they use PBAN first and stopped with it? I want to try someday different kinds of HTPB rubbers (mainly differing in viscosity). Some companies I have found offer a kind of poly BAMO, is it worth it’s price? Every compound with an azide group seems to have a quite high pricetag:o

Do PVC pipes from the hardware store or glass fibre tubes hold up with the pressure of such an motor?

Well I am quite busy at work so I can’t really put these ideas to practice. Nonetheless thank you very much for your ideas