Sciencemadness Discussion Board - ammonium nitrate rocket fuel

ammonium nitrate rocket fuel

UncleJoe1985 - 26-10-2008 at 14:58

Does anybody have any experience with NH4NO3 based rocket fuels? I've tried using sugar as a fuel, but rarely had any success setting it off. It seems the mixture drowns under the water produced when the nitrate decomposes. I know that AN has been successfully used in large rockets (one used magnesium powder as fuel).

DeAdFX - 26-10-2008 at 15:11

The water generated by the decomposition of ammonium nitrate doesn't drown it. Check out richard naka's work on AN rocket fuel. He recommends Al powder/S/AN/Binder. Mg works but costs alot because it is shipped w/ 50% powder and I think their is a haz mat fee tacked on too.

kclo4 - 26-10-2008 at 15:21

Ammonium Nitrate is also hygroscopic, which might explain why it is rarely found for such uses, I guess that causes some problems. Anhydrous Ammonium Nitrate would most likely work the best.

UncleJoe1985 - 26-10-2008 at 15:34

Awesome, I've known about his work before, but haven't seen this page before since it was posted only a few months ago. I'll take a look.

[Edited on 26-10-2008 by UncleJoe1985]

franklyn - 26-10-2008 at 16:37

There is a Yahoo group on this worth a look.
http://tech.groups.yahoo.com/group/NO3-propellants

.

-=HeX=- - 30-10-2008 at 05:46

Here is what I fond on Rogue Science, its Mr. Cool's and NOT mine.

Mr Cool
I've used an AN based fuel, it was:

Ammonium Nitrate..............70% [fertiliser grade]
Powdered Aluminum..............5% [resin additive]
Polyester Resin...................18% [cheap stuff for fibreglass work]
Ammonium Bichromate..........5% [actually, potassium dichromate was used]
Powdered Charcoal................2% [lumpwood barbeque charcoal, reduced to airfloat in a ball mill]

It worked, but was not as good as KNO3/sugar or BP. I only tried a few times, maybe with practice it could be improved, or maybe with a different motor design.
IIRC, it hardly burnt at all in the open, just the resin with a smokey flame. I used a small nozzle and a BP igniting charge up the core to try and get the pressure up.

Another AN mix which apparently works is very simple: 80-90% AN, 10-20% "urethane plastic."

I remember he tried it in a Gyrojet (spin stabilized, canted ports) rocket, and it gave massive thrust and power. I an going to try it once I build a metal engine and get my (NH4)2Cr2O7 (I think thats the formula... Its Ammonium Dichromate.) The Ammon. Dichromate decomposes to mostly gas and some Cr2O3. An excess of Al powder should act as an in situ 'Thermite' reaction, via Cr2O3 + 2Al = Al2O3 + 2Cr. Not sure if the reaction is correct but here is a link to a video of said thermit:
http://www.nakka-rocketry.net/thermites.html#TH9 and it works w/ Mg also. I will be using MgAl in my engine. The prime will be BP in the core.

Here is Mr. Cool's post on its performance:

I made a 1" diameter rocket stabilised using angled jets. I used a paper roll cap to set it off, and BP with a bit of red phosphorous as an igniter because I didn't have any primers. The fuel was AN/Al/resin/ammonium dichromate/charcoal (actually I used potassium dichromate), as described in ALENGOSVIG1's site. I launched it from a cardboard tube with a nail in the bottom. The rocket was put about 1" into the tube, where it was stopped by a nail through the side. A length of string attached to this nail could be pulled from a distance, allowing the rocket to fall and be set off. It went very high very fast, and very straight.

I may copy said rocket exactly as described.

This is his description of how to make the body:

In my opinion, it would be worth making the ammo (not very hard) for an improvised weapon because of these points. For the (very basic) ammo, just get copper tubing, seal one end with epoxy, fill it with a composite rocket fuel, and plug it with a disc of anything easily drillable and fairly strong, e.g. MDF. Then, using a jig, drill a central hole through the rear plug, and two small angled holes opposite each other on either side of the larger, main hole. Pour a little bit of BP in through the main hole, seal the other two holes with molten wax, and push a rifle primer in the main hole.
Once everything is set up you could mass produce these very quickly. It wouldn't matter if the MDF burnt, because by the time it had burnt a significant amount the rocket would have hit the target.

All credit to Roguesci and Mr. Cool for this post.

Liedenfrost - 20-11-2008 at 22:40

A friend of mine living in Eastern Europe is having good results with an AN and Aluminium based propellant.
Here are some details of his propellant:

AN - 60% fine ground (unknown mesh ball milled Fert grade prills)
Al - 20% 50 micron
Neutral (sanitary) silicone - 20%

Isp=239s at sea level.
Density - 1,66g/cm3
a=0.0273
n=0,338
r=1,3mm/s open air
Pressing at relatively low pressure /500-600kg/cm2 / or ramming
Mechanical strength is quite low.
This fuel was tested in motors up to 38mm with great results.

Notable things about this propellant is that it works very well in a vast range of Kn=100-300 and where the pressure is from 1MPa to 5Mpa and burning is stable.
The combustion temperature is very high /2800*C/ and graphite nozzles or inserts are needed.Also powerful igniters are required for good ignition, He's been using Nakka's ''spit fire'' igniters, come to think of it, Nakka is working on AN and Aluminium propellant over on his site.

My friend uses FGAN /fertilizer grade 34-0-0/ ,granulated. It consist 0,5% MgO as a stabilizer according to the information provided by the local manufacturer.

[AN is in the form of rhombohedral crystals at room temperature but changes to monoclinic crystals (larger) when heated above 32 degrees Celsius]

I've been in contact with him since and he has this to add:

''New formula AN,SI,AL. 3N
AN - 67%
NN* - 3% /Sodium nitrate/
Aluminium - 18%
Neutral silicone - 12%

*My friend is from eastern Europe and so NN=''natrium nitrat'' IIRC.

In a small motor 25x150mm with 60g propellant.
Kn value was on the low side ~100.
My small rocket flew seemingly well with burning time around 4s.''

Heres a video that he made of this different propellant.

http://www.youtube.com/watch?v=ZzaL0r1LwXQ''

The mixing process of AN
- I grind the granules up to 0,5mm size
- I dry it in oven at a temperature 90-100*C for about 2 hours
- I grind finally the granules up to 50 microns
- I mix the silicone with Al first,then i add the AN from above
Commence long stirring by hand until it moves from wet sand consistence to thick paste.
The Mixing process is a big challenge,but not impossible.
Pressing by hand or ramming directly to the motor case.
I leave it to cure overnight and then I carefully and slowly drill a core.

In the other formula's 70/20/10 or 70/18/12 with less silicone content,
I drill immediately without waiting for curing.

I use this propellant in small motors up to 38mm without any problems with phase changes of the AN.

Silicone N has much better oxygen balance than HTPB. It releases oxygen with hardening which compounds are very efficient depressants of the exponent “n”.
(I'm not sure what he's trying to say here sorry).

Here's a picture of one of the grains.

[IMG]http://i8.photobucket.com/albums/a30/sequesteredfishy/ANSIAL.gif[IMG]

The aluminum was about 20-30 microns.

I'm sorry if there are grammatical mistakes in this post[I can not think straight right now, too much grog]

Holthof - 2-9-2010 at 23:09

Hey Liedenfrost,

I found the video on youtube before I saw this post on the forum. Currently, I am investigating the use of AN as an oxidizer in rocket propellants and I am very curious to the details of this particular propellant. Could you get me into contact with your friend?

grndpndr - 2-9-2010 at 23:56

The use of AN in various rocket propellants is very exciting! Im anxios to make a file of whats available and read at my liesure.
sadly AN isnt available in the quantity or quality it used to be at least anywhere near here.

Where there a will thers a way however.

DubaiAmateurRocketry - 7-6-2013 at 03:40

If you use Ammonium Nitrate and Sugar, great, your ratio must be wrong.

Because amminium nitrate sucks at donating oxygen, 2NH4NO3 decomposes to give only one Oxygen gas molecule, which is terrible.

You will need at least 80% Ammonium Nitrate by weight in your propellant if your fuel is sugar.

papaya - 7-6-2013 at 04:33

I'm not interested in rockets, however I want to add something interesting I did after some time from opening https://www.sciencemadness.org/whisper/viewthread.php?tid=24...
thread. I'm still looking for AN/fuel/catalyst combination which will burn well under atmospheric pressure (initially wanted to achieve some composition for fuses, without Al or Mg powder). One of experiments was : melted AN with urotropin (8%), when cooled the flakes of that would burn vigorously if placed on Al foil and heated. Later I ground it and added some 5% Cr2O3 catalyst, mixed into rubber glue(chlorinated rubber I think), however glue never hardened since the composition is extremely hygroscopic and becomes WET in open air, but even then it burned quite well. How I came to it is: chromium is a catalyst for AN decomposition, and is also a catalyst for urotropin burning (put some Cr2O3 on dry fuel tablet, ignite, wait to heat it up, then blow the flame - you'll see it continues to burn like cigarette), so it will work both for fuel and oxidizer. I suspect Cr2O3 can catalyze any amine burning reaction as it works also for ammonia gas oxidation. As I said the product made this way is extremely hygroscopic, may be replacing urotropin with urea/other amines/amides may give better result, I cannot test that since have no compounds yet, what do you think?

Fantasma4500 - 7-6-2013 at 04:41

well the water absorbed through air could yield some extra power (ALICE project using ''nano'' aluminium dust and water frozen down)
you might want some very hot initiation source for this somehow

DubaiAmateurRocketry - 7-6-2013 at 05:07

Quote: Originally posted by Antiswat

well the water absorbed through air could yield some extra power (ALICE project using ''nano'' aluminium dust and water frozen down)
you might want some very hot initiation source for this somehow

Nano aluminum, its so hard to make, and you have store in a noble gas can, Aluminum oxide forms around 25 Nano meter so any contact with our atmosphere will screw ur aluminum up for that reaction. The reaction temperature isnt that high and a good thermite could do it.

ErikSedell - 21-10-2024 at 00:01

I know this is a very old thread. Have anyone here tried this or similar composition?

I working on using AN + metal + silicone for a rocket propellant and want to hear about your experiences.

I find this composition very hard to ignite. I use Mg/red iron oxide thermite for now, and sometimes I get it to ignite but not always. I tried KNO3/Boron as well, but it burns so fast it is more like an explosion than a hot flare. Now considering adding Mg and/or Sulphur to the mix to get an easier ignition.

I also find a lot of residue after burning. Like the grain is still there as a hard, porous matrix. I suspect this matrix is something lika glass remnant of the silica in the silicone. I´d rather have all the propellant go out through the nozzle. Could this depend a lot on the silicon used?

Note that my prototype motors/grains are all very small. usually 10 mm inner diameter, sometimes 15 mm. This makes it hard to get a big, potent igniter into the motor.

Quote: Originally posted by Liedenfrost

A friend of mine living in Eastern Europe is having good results with an AN and Aluminium based propellant.
Here are some details of his propellant:

AN - 60% fine ground (unknown mesh ball milled Fert grade prills)
Al - 20% 50 micron
Neutral (sanitary) silicone - 20%

Isp=239s at sea level.
Density - 1,66g/cm3
a=0.0273
n=0,338
r=1,3mm/s open air
Pressing at relatively low pressure /500-600kg/cm2 / or ramming
Mechanical strength is quite low.
This fuel was tested in motors up to 38mm with great results.

Notable things about this propellant is that it works very well in a vast range of Kn=100-300 and where the pressure is from 1MPa to 5Mpa and burning is stable.
The combustion temperature is very high /2800*C/ and graphite nozzles or inserts are needed.Also powerful igniters are required for good ignition, He's been using Nakka's ''spit fire'' igniters, come to think of it, Nakka is working on AN and Aluminium propellant over on his site.

My friend uses FGAN /fertilizer grade 34-0-0/ ,granulated. It consist 0,5% MgO as a stabilizer according to the information provided by the local manufacturer.

[AN is in the form of rhombohedral crystals at room temperature but changes to monoclinic crystals (larger) when heated above 32 degrees Celsius]

I've been in contact with him since and he has this to add:

''New formula AN,SI,AL. 3N
AN - 67%
NN* - 3% /Sodium nitrate/
Aluminium - 18%
Neutral silicone - 12%

*My friend is from eastern Europe and so NN=''natrium nitrat'' IIRC.

...

Sir_Gawain - 21-10-2024 at 08:06

I was experimenting with a hexamine/potassium chlorate rocket fuel and found that adding a small amount of ammonium nitrate dramatically increased the burn rate and ease of ignition. I can’t remember the exact ratios; I’ll have to find my notes.
When ammonium nitrate and hexamine are mixed, ammonia gas is released, and I believe some hexamine nitrate is formed. I found a patent that detailed a high performance explosive made by melting together AN and hexamine. When I tested it, it seemed to outperform ammonal.

Hey Buddy - 21-10-2024 at 08:28

That is very interesting. AN and glycine form a cocrystal at various ratios which have different melting points in the low 100 C range IIRC. The material is broadly referred to as ANGC. It bypasses phase change character of AN and stabilizes it across a wide range of temperature. The patent didn't discuss the matter, but I found in testing the material, ANGC is non-hygroscopic and also serves as a melt cast carrier. It is standard cap sensitive. Low critical diameter. I tested it at around 20 mm diameter x 50 mm height which had no difficulty detonating. It was reported to me by someone else that ANGC can melt NQ similarly to other amino acid explosives.

I would be very interested to read about the patents and any research you could share on hexamine/AN explosives. Especially if you feel they are comparable to ammonal.

Attachment: ANGC_US4746380.pdf (575kB)
This file has been downloaded 51 times

Sir_Gawain - 21-10-2024 at 08:39

Here’s one of the patents:https://patents.google.com/patent/US3247033A/en
It basically entails melting together a 91/9 AN/Hexamine mixture at about 150°C, cooling rapidly by pouring onto a cold metal plate, and crushing the solid through a sieve.

Nemo_Tenetur - 21-10-2024 at 11:22

Quote: Originally posted by Sir_Gawain

This seems to be an unstable mixture. Potassium chlorate in contact with ammonium salts could form self-ignitable Ammonium chlorate:

https://en.wikipedia.org/wiki/Ammonium_chlorate

Sir_Gawain - 21-10-2024 at 11:52

Quote: Originally posted by Nemo_Tenetur

This seems to be an unstable mixture. Potassium chlorate in contact with ammonium salts could form self-ignitable Ammonium chlorate

Yes, I’m aware of that. It probably contributes to the ease of ignition compared to the mixture of just chlorate and hexamine. It shouldn’t be to much of a problem, though I wouldn’t recommend storing it.

ErikSedell - 21-10-2024 at 23:10

Quote: Originally posted by Sir_Gawain

I was experimenting with a hexamine/potassium chlorate rocket fuel and found that adding a small amount of ammonium nitrate dramatically increased the burn rate and ease of ignition. I can’t remember the exact ratios; I’ll have to find my notes.
When ammonium nitrate and hexamine are mixed, ammonia gas is released, and I believe some hexamine nitrate is formed. I found a patent that detailed a high performance explosive made by melting together AN and hexamine. When I tested it, it seemed to outperform ammonal.

I don´t see how this relates to my question. Have you tried any AN-based rocket propellant with silicone as binder and if so, what was your experience?

Microtek - 23-10-2024 at 09:55

I have tried propellants based on the post by Liedenfrost. I dissolved the silicone in a little gasoline and then added the AN (phase stabilized) and Al (3 um) and stirred while evaporating the gasoline. I later iterations, I added varying amounts of granular NG/NC to the mix. The performance of these rockets (about the same size as yours - I was trying to develop a gyrojet like rocket projectile) was amazing. A rocket 12 mm in outer diameter and 40 mm long, stabilized with a stick would accelerate so rapidly that you couldn't follow it with you eyes. Looked a lot like a rifle firing tracer rounds. The launch would leave not just a scorch mark on the ground but an actual hole from the exhaust.
The addition of ballistite granules to the mix obviously helped with ease of ignition which was not problematic. I assume you are using a hollow core grain design? I made my mandrel with a cruciform cross section to keep a fairly constant thrust profile.

Hey Buddy - 24-10-2024 at 17:27

Quote: Originally posted by Microtek

I have tried propellants based on the post by Liedenfrost. I dissolved the silicone in a little gasoline and then added the AN (phase stabilized) and Al (3 um) and stirred while evaporating the gasoline. I later iterations, I added varying amounts of granular NG/NC to the mix. The performance of these rockets (about the same size as yours - I was trying to develop a gyrojet like rocket projectile) was amazing. A rocket 12 mm in outer diameter and 40 mm long, stabilized with a stick would accelerate so rapidly that you couldn't follow it with you eyes. Looked a lot like a rifle firing tracer rounds. The launch would leave not just a scorch mark on the ground but an actual hole from the exhaust.
The addition of ballistite granules to the mix obviously helped with ease of ignition which was not problematic. I assume you are using a hollow core grain design? I made my mandrel with a cruciform cross section to keep a fairly constant thrust profile.

I had some trouble locating the Liedenfrost post referenced here. Would you mind sharing information on the propellant in more detail? I am used to thinking of Si as a reduced powder, in rocketry is this referencing actual silicone as in the adhesive polymer? Particularly I was curious about the ratios that seemed effective on the NC/NG?

[Edited on 25-10-2024 by Hey Buddy]

Microtek - 25-10-2024 at 02:15

The post I'm referencing is the seventh in this thread. Silicone (PDMS) is the binder but also apparently has some effect on the burn rate exponent, which makes this propellant less likely to CATO. I used ballistite with a 50% NG content, and included about 20 % of it in the propellant. I found that adding a little (1-2 %) PIB to the mix gave better mechanical properties.

I granulated the mix as the gasoline evaporated and once only trace amounts of the solvent remained, I would press it into a mold around the mandrel. Then I removed grain with mandrel from the mold and allowed the PDMS to cure fully (sometimes with heating) before removing the mandrel.

sarinox - 30-10-2024 at 05:00

Hello all,

I recall reading in an article that ammonium nitrate (AN) can exist in various solid-state phases, and that one phase can be stabilized by melting it and introducing certain salts. Although my memory of the details is somewhat vague, this process seemed to involve modifying the crystalline structure to maintain phase stability.

Previously, I hesitated to attempt this method myself due to concerns about the risks associated with heating AN to its molten state and adding salts to alter its crystal structure. Consequently, I decided not to pursue this approach experimentally.

I’m sure some of you are familiar with this process, but I wonder if any of you have actually tried altering the crystalline structure of AN?

ErikSedell - 30-10-2024 at 05:00

Quote: Originally posted by Microtek

Thank you for sharing your experience! This is great input. Was your small rockets just a single core or multiple grains? I tried multiple grains, but I´ve discovered my AN is of subpar quality. Need to get/synthesize a better batch.

What kind/brand of silicone did you use? What kind of igniter for the original formulation (without ballistite, which I won´t be able to source.)

What nozzle design did you use? i.e Kn value and material? I have so far used mortar nozzles, but the erosion/melting is substatial so I will try adding a graphite insert into the mortar.

Best regards,

Erik

Microtek - 1-11-2024 at 14:35

I used silicone putty for bathrooms and I did just a single grain. Both ends of the rocket were machined from steel rod on my lathe and screwed into the body. The nose part had a small reservoir which I filled with an easily ignitable thermite pyrogen, I think it was based on CuO/Mg. I don't recall the Kn, but the throat was around 2 mm IIRC. The burn time was much less than a second, maybe around 0.2 seconds, and it seemed that the SiO2 tended to condense on the nozzle rather than erode it (at least in static tests).

ErikSedell - 5-11-2024 at 00:16

Quote: Originally posted by Microtek

I used silicone putty for bathrooms and I did just a single grain. Both ends of the rocket were machined from steel rod on my lathe and screwed into the body. The nose part had a small reservoir which I filled with an easily ignitable thermite pyrogen, I think it was based on CuO/Mg. I don't recall the Kn, but the throat was around 2 mm IIRC. The burn time was much less than a second, maybe around 0.2 seconds, and it seemed that the SiO2 tended to condense on the nozzle rather than erode it (at least in static tests).

Thank you! Did you use steel for the body as well? I like the idea of containing the igniter comp in the nose plug. Working on some new AN now and i´m eager to get this propellant to work!

Microtek - 5-11-2024 at 00:40

I generally used aluminum tube for the body, but did do a few with steel bodies. I didn't notice any compelling reason for using steel in the tests I did.

ErikSedell - 12-11-2024 at 00:19

Thank you for your answers, will report back when I have tried again!