ALICE

[dagabu]

I've tested two more fuels and have so far best liked the burn of one using both Star Al & -200 Mg. It has a steady and moderately fast burn. So far it's the first I've tried that looks like it could lift a rocket.

 

Ignition is still a big problem. A thermite ignitor did no good. In fact when the fuel was cast into a grain and the thermite failed, I was unable to ignite it directly with a torch until I fractured the grain to create a rough surface. Short of filling the core completely to the brim with thermite I'm not sure what to do next. I have a fuel now that's got me excited, if only I could light the stuff from inside a core.

 

There was a metal fueled rocket that launched before us at a meet in Nevada in '95 that had an igniter that looked solid and went all the way up to the top of the spindle. An aluminum cap (can only guess here) was at the base of the igniter and the whole rocket slid down the rail and sat on this igniter and cap assembly. We were 500' away, the video was tape back then and I dont recall the specifics but it plays out like this.

 

The switch was flipped and the igniter started the top of the igniter tube, some smoke started and slowly built up and then over a 5 second period, the smoke thickened, a little flame appeared and then the rocket started to lift just an inch for a second and then finally took off. The whole ignition took a good ten seconds to complete.

 

Maybe that is what you need, a stepper approach with a way to keep the fire inside the rocket motor. Just brain storming a little

[NightHawkInLight]

Yeah I suppose the problem with ignition could easily be duration in addition to the temperature. If so, that's a bit of a problem. Longer duration gives more time for heat transfer to the entire grain which might melt a good portion before ignition. I guess before I preform many more tests on the fuel itself I should go through a few ignitor designs. Thermite has got to be hot enough, if only I can figure out a way to direct that heat more directly into the fuel.

 

I've done enough to have learned my lesson about note taking when doing things like this, so I've been keeping track of my progress. Here's what I've got so far:

 

Molar Mass:

H2O - 18

Al (StarMolecule) - 27 -> Al2O3

Mg (-200) - 24 -> MgO

 

2"x3/4" grains with 1 1/2"x1/4" core. Fruit pectin is Ball brand and contains dextrose, fruit pectin, & citric acid. Evaporation of water causes problems with the ratios, so all compositions are mixed in sealed bags before pouring in the grain and freezing. Tubes and rod for coring are pre cooled below 0°f. Composition is brought as close as possible to 32°f and mixed quickly before pouring and freezing.

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1.

 

H2O - 50

Al - 50

Fruit Pectin + 5

 

Slow burn, difficult to ignite. BP/Mg ignition was ineffective.

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2.

 

H2O - 50

Al - 25

Mg - 25

Fruit Pectin + 5

 

Burned vigorously, but bubbled when mixed. Likely cause is citric acid in the gelling agent acting on the Mg. Not tested in a grain.

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3.

 

H2O - 50

Al - 25

Mg - 25

 

No reaction from Mg while mixing. Some bubbles were on the surface of the frozen grain, possibly from Mg, or air that was trapped when poured - Very minor regardless. Red iron oxide/Al thermite ignitior used deep in grain - Failed. Could not be ignited when cast into a grain. Pieces burned rapidly when it was cracked and ignited via butane torch.

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4.

[pillyg]

Hum. I think this could work if it could be ignited.

I was looking here ( http://en.wikipedia.org/wiki/Pyrotechnic_initiator ) but I dont think there is anything hot enough but you probably know better than me.

[dagabu]

NHIL, I think I found your solution.

 

http://rinconrocketry.com/airstart.htm

[NightHawkInLight]

NHIL, I think I found your solution.

 

http://rinconrocketry.com/airstart.htm

 

Ooo, cool. I never thought of dipping ematches so that a good length of the wire gets coated. I'll have to try that out when I get moving on this project again. Thanks!

[dagabu]

I would coat the entire thing with a this coat of NCL though.

[NightHawkInLight]

I would coat the entire thing with a this coat of NCL though.

Certainly. Especially if used in an engine with water in the fuel. Wouldn't want moisture getting into the igniter.

[THEONE]

Add some BP with Mg into your NCL. It will burn more hot Edited September 15, 2012 by THEONE

[Short5]

This is all very interesting. I have a question though. I am picturing a frozen chunk of Aluminum and water. Doesn't it just melt back to a slurry as soon as it gets hot? I picture the whole thing getting mushy as it heats up and reacts. How is it that it doesn't lose structure as it warms from the burn?

[pillyg]

I have not tested this but I am sure it will be kept in a freezer/cooler until launch. I also assume something similar to pykrete would happen causing the "slurry" to become super hard and stay frozen longer than normal ice.

 

The motor burns so fast that I don't think you would have to worry about it losing structure during the burn.

[THEONE]

It is not possible that type of grains will crack from the chamber pressure ?

 

Try some magnilium, it ignites easier than AL and i believe will not react with the water so no bubbles

Edited September 17, 2012 by THEONE

[THEONE]

Guys what about a solution of ammonium nitrate and water in case of puree water... Edited September 18, 2012 by THEONE

[MetalNeko]

This is pretty awesome. Sort of reminds me of the H2O2/Al/xanthan gum peroxide watergel. Has anyone tested this to see what kind of ignition temperatures are required?