NC-bound pressed CuO-MgAl thermite rockets

[aeon]

Thought i'd introduce myself here with my first post by providing some info that hopefully is interesting and/or useful.

 

Propellant used initially (which works, to cut to the chase):

 

4:1 CuO, superfine : MgAl, -60mesh

Bound with 5% w/w pyro nitrocellulose (fluffy, slightly clumpy white powder), wetted with just enough acetone to produce a pliable dough.

 

Rocket dimensions were 30mm ID, with 10mm wide core tapering more or less linearly to ~6-7mm at end of core, core length is ~100mm, 2x web thickness (distance of core to inner wall) pressed above top of core, so once core is exhausted will continue to burn in coast phase for roughly same duration as high thrust phase.

Was pressed at 80psi. 10mm clay plug pressed on top. Mandrel setup was steel.

 

 

This was tested in less than optimal conditions, namely that I hadn't allowed the solvent to evaporate (but the grain was super smooth and hard still, like injection molded plastic) so would expect burnrate to be a little higher if one were to allow this to happen.

Anyway, this was ignited with a piece of green star taped to visco fuse inserted simply at the nozzle end of the core, as it was expected the flame would propagate very quickly upward once the reaction started.

This proved mostly to be the case; upon ignition the nozzle end flared superbright but not making a thrust sound for around half a second, then the flame shape rapidly changed and acceleration begun. The flame as you would expect was really, really bright, and the exhaust smoke a deep copper colour. During flight the thrust pulsed rapidly, leaving neat discrete clouds of copper in the sky. Total burn time was around 5 seconds. It did not go that high (maybe few hundred meters), but this propellant is hardly an ideal exhaust gas, being really high molecular weight. Of course, some of the copper is in gas phase due to the extreme temperature so that contributes toward useful thrust, and you get some more usual gas moles like H2O, H2, N2 CO2, CO etc from the NC burning, but it's not much of a contribution at only <5% w/w.

This would probably work better with a longer core, and with proper evaporation of the solvent. Nonetheless a fun experiment.

 

A later composition was tried with the addition of 10% ammonium perchlorate (NH4ClO4, 200 micron) to the aforementioned formula, using the rationale of more gas moles and so better performance, but when this was tried (multiple times!), ignition occured but was extingushed when it chuffed. I think the gas production threw the hot reaction products off the surface. Perhaps if you could get the whole core lit at once it would be self sustaining.

Edited August 30, 2011 by aeon

[psyco_1322]

First I will state that Cuo/Al is very very impact sensitive, and I would guess that other metals would be the same.

 

Second, your magnalium is a tad coarse if you want a fast burning fuel that will get your rockets up there. If you use something around 200 mesh or finer, with care, your burn rates should increase and you should see some significant changes in the thrust.

 

I have personally made a smaller version on my 4oz whistle tooling. Core in .25" wide and about 2.25" long, motor ID is .5" obviously. Fuel I used was CuO:Al, 3:1, dark Al, NC bound as well. The rocket flew just as well as a whistle and the delay burnt up very fast. This mix by itself, with and with out the binder, is like flash powder, and should be regarded more dangerous due to higher sensitivity to impact.

 

I believe that there is plenty of research to be done on these fuels and someday they might join the more commonly used ones we all know.

[dan999ification]

isnt this essentially one very large dragons egg?

 

dan.

[Juiceh]

Where can one find "pyro nitrocellulose (fluffy, slightly clumpy white powder)" for sale?? The only NC I have and can find online is the green canned stuff.

[moondogman]

Firefox has it I believe I would think nc inthe can would still work.

 

Steve

 

Where can one find "pyro nitrocellulose (fluffy, slightly clumpy white powder)" for sale?? The only NC I have and can find online is the green canned stuff.

[moondogman]

I bet a bit of whistle for the first increment would help it get lit faster and give it a boost.

 

Steve

Edited October 13, 2011 by moondogman

[psyco_1322]

No, dragon eggs are not made of CuO and Al, they have other chemicals in them also, and act way differently.

 

I would suggest FireFox as well. Although I make my own and can't vouch for their product.

[californiapyro]

dragon's eggs must contain a bismuth or lead oxidizer as far as I know. the copper oxide acts as a secondary oxidizer, and aluminum isn't required. mg/al is much better

[anapogeetoofar]

I've made these with MnO2 and fine (-325mesh) Mg. Quick little boogers, and retina burningly bright. Some other guy had the same Idea as me and put a video up on the youtubes, I'm sure you can find it.

I might try one of these with CaSO4/Mg and the like, for shittings and gigglings.

Too expensive for anything other than occasional abuse though. A shame.

 

Oh, and don't try Mg/S or dark Al/S in a rocket, there are far easier ways to make sautes.