how to make apcp

[emoskven]

hi i am new to making apcp and i am wondering how you make it....the chem formula, procedure, materials and all...thanks

[WSM]

hi i am new to making apcp and i am wondering how you make it....the chem formula, procedure, materials and all...thanks

 

I may be wrong but this topic may be better answered in the rocketry section (assuming you do mean ammonium perchlorate composite propellant).

 

WSM

[Nessalco]

Start with the book "Experimental Composite Propellants" by Terry McCreary. That gives an excellent overview of the process, materials, equipment requirements, formulas, and pitfalls. It's not a cheap book, but making good, safe APCP is not a particularly simple task.

 

Kevin

[emoskven]

thanks....does apcp vary much..i mean in burn time and impulse and stuff.....i made simple liquid engines and i could vary my flow rate of the fuel to get the maximum amount of thrust i wanted...is it possible to do the same with apcp?

[WSM]

thanks....does apcp vary much..i mean in burn time and impulse and stuff.....i made simple liquid engines and i could vary my flow rate of the fuel to get the maximum amount of thrust i wanted...is it possible to do the same with apcp?

 

It has mostly to do with grain geometry and chemistry if the same physical parameters of the materials used are maintained. The solid propellants aren't "throttleable" but a hybrid (solid fuel & liquid oxidizer) is to a degree. Striking a balance is the key to success with hybrids, though.

 

WSM

[emoskven]

i have heard of people using different binders...what does this exactly do if i vary which binders i use?

[TYRONEEZEKIEL]

You have 2 kinds of binders in APCP. HTPB or PBAN. PBAN is what NASA uses. It has to be heat cured to harden. HTPB uses isocyanates and R45 to cure. This works like epoxy and cures over time.

[dagabu]

You have 2 kinds of binders in APCP. HTPB or PBAN. PBAN is what NASA uses. It has to be heat cured to harden. HTPB uses isocyanates and R45 to cure. This works like epoxy and cures over time.

 

You can also use off the shelf silicone caulk for a ghetto style binder, some experimentation has to be done to get the right mix but it works as well as DER331 in my experiences.

 

-dag

[Jonathan]

A very small piece (far smaller than 1.0g) of the APCP I've made will take off zooming like a rocket when ignited. The mixture BY VOLUME is:

 

2 parts NH4ClO4

1 part Al

1/2 part S

 

The binder is silicone.

 

I've made this in small batches and have not tested it in a rocket. I'm pretty sure a cardboard tube with a bentonite nozzle couldn't handle it.

[AzoMittle]

Jonathan even if it could sustain the pressure (which it wouldn't) you would still have issues with it burning through the tube in most cases. What kind of Al are you using? Any chance you could either post a video or preferably do some thrust tests? If you could actually give us an Isp we could figure out some more numbers.

 

Speaking of ghetto apcp binders I've heard of people using various 2 part epoxies, bondo, every sort of glue under the sun, and even asphalt sealer. I can't speak to effectiveness of them but the point is you *can* use damn near anything that will give you a decent solidified grain. I love binders.

[Jonathan]

AzoMittle,

 

I'll get to work on trying on determine the ISP. Vid is beyond my capabilities.

 

I can tell you a 1/2" I.D. cored and nozzled hand-made motor tube filled with a lightly tamped DRY mix produced a teeth rattling explosion. This experiment, BTW, was a static test.

Edited September 25, 2013 by Jonathan

[Seymour]

What you two are saying sounds familiar, though it does not match my personal experience.

 

I've been told by many people, particularly those who successfully make high power motors with Aluminium cases and graphite nossless, that "APCP motors can't be made with cardboard cases and clay nossles". They tell me they 'just blow up' as soon as you get close to producing thrust.

 

I'm not sure what I'm doing differently, but in my experience they work, and they work excellently! I treat the mixture like an exotic firework rocket. That is, I press the dry powder in to a case with a clay plug at both ends, and drill it out to make a core. No binder used, since there is no need. I'm making a firework rocket!

 

Instead of "binder" I'm using powdered phenolic resin (Resinox). Of course, there are plenty of two part liquid phenolics that can be used as a binder, but this seems to be pointless. With these small firework type rockets, what benefit do you have from a rubbery cast fuel? None as far as I know, but you sure have a lot of problems making it bond to the tube and in plugging the top end. You can't press clay on top of rubbery APCP easily. It acts as a fluid and causes many problems.

 

Resinox seems to be a nice 1/1 replacement for HTPB when it comes to burning.

 

Why do you guys have these failures? I think a lot of it has to do with the use of rubbery binders. Secondly, the fact just is that with all kinds of firework rockets, inexperienced builders are going to have catos. Experienced builders do too! Lots of them. Quite likely they will have lots of catos before they get a success. Even if they have built many high powered motors successfully, they may not know how to make firework rockets properly. I've seen this a lot.

 

Then people have catos and say that it cannot be done! Other people read this and it matches what they found, and soon enough you have a bunch of people saying "APCP in cardboard cases cannot work" simply because it didn't for them, and next thing everyone believes it! Hopefully I can help reverse this, though I'm sure there are other successful attempt out there.

 

I made em, and not just that, I made em coloured. My friend who I make em with even made very successful 3/4" versions. Here are some notes and formulas:

 

Ammonium perchlorate based romance with floral colour.

 

Ideally Mg is used instead of MgAl alloy powder. Dichromate treating is desired for either metal.

I also like to mill some Ammonium dichromate with the Ammonium perchlorate (1%)

Successful core burning rockets have been made in the ½” size using a core 30mm deep and 4mm diameter.

 

¾” size 5.5mm by 55mm has been tested, and longer cores should be tested.

Yellow

44% AP

22% BN

14% SrN

14% Resinox

5% MgAl

1% Fe2O3

 

Lime

 

50% AP

25% BN

15% Resinox

5% MgAl

4% SrN

1% Fe2O3

Green – well tested

50% AP

30% BN

14% Resinox

5% MgAl

1% Fe2O3

 

Lavender

70% AP

15% Resinox

9% SrN

3% MgAl

3% CuCO3

 

Cerice – well tested

54% AP

25% SrN

16% Resinox

4% MgAl

1% CuO

 

Red

47% AP

32% SrN

15% Resinox

5% MgAl

1% Fe2O3

Orange

 

52% AP

20% SrN

15% Resinox

7% BN

5% MgAl

1% Fe2O3

Edited September 26, 2013 by Seymour

[Jonathan]

Seymour,

 

I suspect the key to your success with APCP and cardboard tubes is your use of phenolic resin. Just found a U.S. supplier of finely powdered phenolic resin and ordered a gallon.

[Seymour]

I agree that the resin I use is a great advantage. Resinox seems to have a magic touch. It burns amazingly with every oxidiser I've tried. What a gorgeously promiscuous fuel/binder it is!

 

I also think that milling the Ammonium perchlorate is important too. From my exposure to experimental rocketeers I have noticed that often APCP uses quite large crystals of Ammonium perchlorate. It seems that in the high pressure of a "proper rocketry motor" these large particles are able to fully and cleanly decompose. Thud the advantages of higher density, and perhaps a slowed burnrate make the use of these large crystals worthwhile.

 

However I suspect that they also contribute somewhat to some of the characteristics typical to APCP, like chuffing when motor ignition is not complete enough to get it up to pressure.

 

In these firework motors of course the pressure they run at will be a hell of a lot lower. I think by milling it fine (but not too fine, it can explode in the mill and milling it below a certain particle size is often known to be involved in these accidents) the pressure at which it will burn stably is likely to be greatly reduced - in to the range where we can have success.

 

2 parts NH4ClO4

1 part Al

1/2 part S

 

The binder is silicone.

 

As in the 1/2 part S is Silicone?

[AzoMittle]

think by milling it fine (but not too fine, it can explode in the mill and milling it below a certain particle size is often known to be involved in these accidents) the pressure at which it will burn stably is likely to be greatly reduced - in to the range where we can have success.

 

I don't get the chance to experiment often, and with APCP I haven't even started. For safety's sake can you give a ballpark of when "fine" becomes "too fine / can explode"? No problems with drilling the core? I think the (common) problem with paper/clay catos is due to the focusing in on high Isp motors, if the goal is to produce a pyro rocket (as opposed to a high-power) you're already going to probably want to reduce the power; no need to have your rocket gone before you can blink that is if you want those pretty lights. Of course I'm just throwing this out there with nothing to truly base it on.

 

Besides resinox have you found any workable 'dry' binders? Or anything else interesting?

 

Also thanks for the colored formulas, those look like fun

[Nessalco]

I've been told by many people, particularly those who successfully make high power motors with Aluminium cases and graphite nossless, that "APCP motors can't be made with cardboard cases and clay nossles". They tell me they 'just blow up' as soon as you get close to producing thrust.

 

I'm not sure what I'm doing differently, but in my experience they work, and they work excellently! I treat the mixture like an exotic firework rocket. That is, I press the dry powder in to a case with a clay plug at both ends, and drill it out to make a core. No binder used, since there is no need. I'm making a firework rocket!

 

First off - good work. Don't change what you're doing because of these comments!

 

What you are making is not APCP, and does therefore does not act like APCP, which is specifically a composite propellant. Unless you're adding a binder to it, and making a composite with a solids loading greater than 87% it is not APCP. It may be a cool rocket propellant based on AP, but....

 

One important aspect of the function of APCP is acceleration of burn rate under pressure. The usual case pressures are in the 500psi range, with high performance motors occasionally reaching 1000psi, which is why folks say cardboard is a non-starter. A properly designed APCP motor in a 1# rocket case (if it could stand the pressure) would easily lift 5 pounds to 1000'. APCP has a lot of potential.

 

FWIW, the high-power rocket guys buy 200u AP because that's what they can get without a permit- they mill it down much finer than that.

 

Kevin O

Edited September 27, 2013 by Nessalco

[Jonathan]

Seymour,

 

The "1/2 part S" is 1/2 part sulfur. I don't weigh or otherwise measure the silicone. I've learned by trial and error to squeeze out a ribbon that's just enough to bind the dry ingredients. The finished product when cured has the consistency of a pencil eraser.

Edited September 27, 2013 by Jonathan

[Seymour]

The "1/2 part S" is 1/2 part sulfur. I don't weigh or otherwise measure the silicone. I've learned by trial and error to squeeze out a ribbon that's just enough to bind the dry ingredients. The finished product when cured has the consistency of a pencil eraser.

 

Jonathan, I know what you mean about the consistency being like a pencil eraser, a very good way of describing it While not Silicone bound, I've actually used chunks of HTPB bound APCP as a pencil eraser

 

I'm not that surprised that you had a good firecracker experience with that mix. I know silicone is a fast fuel with AP, and I must say, though Resinox is probably my favorite, with a few % MgAl, I am quite fond of using it in stars. It's not fully tame though. I had a large, poorly pumped star act very enthusiastically. I assume as a result of small cracks in the star due to the poor compaction the star burned for a few moments and made a small flash and a loud bang. Just a star I lit on the ground! I'm sure the Dark Aluminium and Copper catalysts helped. I've also had this behavior from partially degraded AP strobes. Somewhat unsettling.

 

While I'm sure you can become quite consistent by measuring by eye, or even adding until the consistency is perfect, you will be able to advance much further in this hobby if you weigh things, especially when it comes to rocket fuels, where deviations in burn rate and sensitivity to pressure can have much more effect on performance than other areas of pyrotechnics. I can't deny that I have been known on many occasions to make unimportant things like a bit of thermite to burn through a can to pass the time, or coloured campfire mixes with a 'handful of this and two handfuls of that' strategy, but in anything important it's not to be skipped. Plus it means that when you have that perfect rocket launch you can do it again exactly, and not have to hope a $ or two change won't push that over or under some lines.

 

First off - good work. Don't change what you're doing because of these comments!

 

Thanks Kevin. If I change anything due to your comments it will only be to improve

 

What you are making is not APCP, and does therefore does not act like APCP, which is specifically a composite propellant. Unless you're adding a binder to it, and making a composite with a solids loading greater than 87% it is not APCP. It may be a cool rocket propellant based on AP, but....

 

I'm not fully familiar with the limits in the definitions that the rocketry pyros use, so I could well be quite wrong here. I have a fair bit of exposure to some of that community, but not a very active interest with rockets that you get back to fly another day.

 

My understanding was that, for general use of the world, composites were basically a material made up of several component materials each with different properties. I understand that this is very widely encompassing, making most things composites that we find in day to day life falling under the definition, but it seems to be accurate. Pretty much all firework compositions would, surely?I've seen concrete cited as a composite, so surely by that definition star mixes count.

 

However I accept that there may be definitions specific to the description of Ammonium Perchlorate Composite Propellant. The requirement for it to be a polymer bound mix that 'cures' is a possibility that comes to mind. People talk of "solids" and "binder", kind of classifying the binder as other than solid. Perhaps I could cross the boundary into this definition when I confess that I have added some solvent to granulate the mix, which my friend and I have done, partially to keep the dust down, but also to bind in to an extent. Very little is added, only a percent or two, but under pressure this has a significant effect on 'binding' it. The performance is similar dry or 'wet', though I could believe that the solvent strengthens the grain enough to push it a bit further.

 

I know that other compositions with AP and PVC, pressed with solvents have been described to me as APCP.

 

Why the limit of 87% solids? I understand that using most binders having only 13% binder is on the very low side. Has some organization decided to set this as a rule for some reason?

 

One important aspect of the function of APCP is acceleration of burn rate under pressure. The usual case pressures are in the 500psi range, with high performance motors occasionally reaching 1000psi, which is why folks say cardboard is a non-starter. A properly designed APCP motor in a 1# rocket case (if it could stand the pressure) would easily lift 5 pounds to 1000'. APCP has a lot of potential.

 

I definitely don't think a card case can produce high end APCP motors, with the possible exception of small, like ABC motor range. If you want max performance, it's not the thing to do. If you want high reliability because you want to be really careful with you $4k of electronics you might feel better with metal and graphite too. I've seen quite a few legit high power launches myself too, and I definitely agree on the potential it has. I don't think you could use a cardboard tube in any large motor, not with any normal paper!

 

However with high quality tubes, and keeping the size small I think most of it's potential to be achieved. While I expect 1000psi is obviously unattainable, and I would not put my money on 500PSI with what I actually know here, I've been told that the benefits of running APCP at high pressure are not great (compared to closer to standard). Definitely worthwhile if you are going for all the performance you can get (a quest I respect), but depending on formulation I'm guessing 10-30% gains?

 

My second card is formulation. AP really seems to like resinox, and seems to burn a good deal faster than it does with most fuels, and with a bigger flame, and a very clear flame. Of course I know that the rtange of APCP burn rates go from less than a milimeter a second to centimeters a second in open air, compared to the average of, I'm guessing 2mm/sec, I'd say that it's a fast on it's own. With enough of the right catalysts it is even faster.

 

While there is definitely possibility for a steepening in the pressure/burn-speed curve at higher pressures than I've forced upon it I'm quite impressed by how little pressure has affected it in the past. With the green formula in 1/2" cases I've pushed the core diameter a bit smaller, to 3.5mm, and it flew successfully, despite the massive increase in surface with it not exploding at any point (bonus), and carrying an identical second stage, and it took off about as fast as my 6/3/1 core burners. While that's hardly going to win me any heavy lifting awards, frankly that's because of the terrible geometry. You're never going to be able to carry anything serious with the initial thrust such a small fraction of the final thrust.

 

I'm really guessing here, but I suspect that you may be able to get higher efficiency at lower pressures if you use faster propellants. I'm a bit out of my depth though, I'm not a rocket scientist. If that's the case then I think there will be some help in using the more highly catalyzed versions. The Cerece for example, with a % Fe2O3 flies in end burners, as can the Lavender.

 

FWIW, the high-power rocket guys buy 200u AP because that's what they can get without a permit- they mill it down much finer than that.

 

Some of the guys I've come across have milled a fraction to a certain level for it to fit between the coarse stuff for bimodal loading. You might be able to confirm that there are some who use a third grade for trimodal! I have seen APCP with mostly or all coarse product, and I was quite impressed with how much better it burned than if you tried that with a normal firework composition. However my experience with firework mixes tells me that AP mixes burn a lot better when it's silky fine, so I'd easily believe that most people do that for APCP too!

 

I assume that there is a restriction on selling AP fine because it can be unstable, catching fire and stuff? If so, 200 micron as a limit seems to be a bit on the chunky side!

 

I don't get the chance to experiment often, and with APCP I haven't even started. For safety's sake can you give a ballpark of when "fine" becomes "too fine / can explode"? No problems with drilling the core? I think the (common) problem with paper/clay catos is due to the focusing in on high Isp motors, if the goal is to produce a pyro rocket (as opposed to a high-power) you're already going to probably want to reduce the power; no need to have your rocket gone before you can blink that is if you want those pretty lights. Of course I'm just throwing this out there with nothing to truly base it on.

 

Besides resinox have you found any workable 'dry' binders? Or anything else interesting?

 

Also thanks for the colored formulas, those look like fun

 

My pleasure, I hope you enjoy them

 

I'm not very certain of how fine it really needs to be to become hazardous. Under ten microns sounds familiar, but is an absolute guess. Perhaps sub micron. I've just milled it for however long it takes to become smooth between the fingers and stopped there, an hour or two, or less, depending on your mill. Remote milling is advised.

 

I drill cores out by hand typically. I typically drill out rockets like whistle, AP rockets, and boosted BP rockets by hand. With BP I'll use a power drill, being careful of the motor showering out sparks, and where the powder falls. Just because I have ten fingers does not make this entirely safe though.

 

I get what you say about lowering the power so you can see some of the colour. To be perfectly honest I've burned more mix with these formulas using it as a lance or fountain or Catherine wheel mix than I have in rockets. I have formed a special bond with the pretty colours and fragrant smoke. Another option is top use a typical short duration firework payload carrying geometry (long wide core) and a massive payload, so it has a low apogee.

 

Probably my favourite "dry binder" for fireworks rockets is plain old paraffin wax. Used just like vasalene or oil is in whistle rockets, it's also good in all sorts of other rocket fuels to keep down the dust, waterproof and provide a more durable grain. My current favourite rocket mix is 60% BP, 30% 7/3 flash with dark flake, and 10% MgAl. 1-2% wax makes fine end burners and nossleless rockets. 4-5% wax makes almost scary cored nozzled rockets. I have been thinking of some kind of whistle with MgAl or dark flake added, and then add wax until you can core it, and have a clay nossle. They should be ruthless.

[mikeee]

Seymour,

 

On your BP rockets (60BP, 30Flash, 10MgAl, 2Wax) do you ram or press these?

What kind of solvent do you use to mix the Wax into the mix with?

What pressures do you press the rockets to?

[Seymour]

I would not ram this mix! Only pressing for me.

 

Solvent used is basically whatever alkane type solvent I have on hand. You know, like hexane, heptane, octane... If you don't have access to pure alkanes then all sorts of day to day alternatives exist, like camping fuel, petroleum...

 

Pressure? I suck at this question. Less than is required to damage the tube, not less than half this pressure. I don't press 19mm ID rockets with a sleeve. Nor have I ever done a calculation to see what pressure it being exerted on the fuel, even though I could easily do so.

 

My rockets work quite reliably, and when it comes to the mechanics and details of most tools I actually get bored pretty quickly. For example, beyond being able to use them, I have almost zero interest in firing systems.

 

Have you made whistle rockets? I make them and these rockets pretty much exactly the same way (same rather wide range in pressure based on intuition as much as anything and no sleve). I'm sure if I started making really serious rockets I'd need to get my act together and start calculating pressure, using a sleve and probably doubling or tripling the pressure, but for what I want I'm happy. I can comfortably make 1lb rockets which carry 4" shells using my present chilled out methods. I'm happy with that for now.

[mikeee]

Seymour,

 

Sounds good, I use a hydraulic press for most of the rockets I make.

Have been milling a bunch of different charcoal and black powders the last couple of weeks.

Ready to start on some different type black powder rockets, have been making whistle rockets mostly.

Want to make a few hybrid rockets with BP & Whistle and a few like you are making along with straight BP.

[ddewees]

What you two are saying sounds familiar, though it does not match my personal experience.

 

I've been told by many people, particularly those who successfully make high power motors with Aluminium cases and graphite nossless, that "APCP motors can't be made with cardboard cases and clay nossles". They tell me they 'just blow up' as soon as you get close to producing thrust.

 

I'm not sure what I'm doing differently, but in my experience they work, and they work excellently! I treat the mixture like an exotic firework rocket. That is, I press the dry powder in to a case with a clay plug at both ends, and drill it out to make a core. No binder used, since there is no need. I'm making a firework rocket!

 

Instead of "binder" I'm using powdered phenolic resin (Resinox). Of course, there are plenty of two part liquid phenolics that can be used as a binder, but this seems to be pointless. With these small firework type rockets, what benefit do you have from a rubbery cast fuel? None as far as I know, but you sure have a lot of problems making it bond to the tube and in plugging the top end. You can't press clay on top of rubbery APCP easily. It acts as a fluid and causes many problems.

 

Resinox seems to be a nice 1/1 replacement for HTPB when it comes to burning.

 

Why do you guys have these failures? I think a lot of it has to do with the use of rubbery binders. Secondly, the fact just is that with all kinds of firework rockets, inexperienced builders are going to have catos. Experienced builders do too! Lots of them. Quite likely they will have lots of catos before they get a success. Even if they have built many high powered motors successfully, they may not know how to make firework rockets properly. I've seen this a lot.

 

Then people have catos and say that it cannot be done! Other people read this and it matches what they found, and soon enough you have a bunch of people saying "APCP in cardboard cases cannot work" simply because it didn't for them, and next thing everyone believes it! Hopefully I can help reverse this, though I'm sure there are other successful attempt out there.

 

I made em, and not just that, I made em coloured. My friend who I make em with even made very successful 3/4" versions. Here are some notes and formulas:

 

Ammonium perchlorate based romance with floral colour.

 

Ideally Mg is used instead of MgAl alloy powder. Dichromate treating is desired for either metal.

I also like to mill some Ammonium dichromate with the Ammonium perchlorate (1%)

Successful core burning rockets have been made in the ½” size using a core 30mm deep and 4mm diameter.

 

¾” size 5.5mm by 55mm has been tested, and longer cores should be tested.

Yellow

44% AP

22% BN

14% SrN

14% Resinox

5% MgAl

1% Fe2O3

 

Lime

 

50% AP

25% BN

15% Resinox

5% MgAl

4% SrN

1% Fe2O3

Green – well tested

50% AP

30% BN

14% Resinox

5% MgAl

1% Fe2O3

 

Lavender

70% AP

15% Resinox

9% SrN

3% MgAl

3% CuCO3

 

Cerice – well tested

54% AP

25% SrN

16% Resinox

4% MgAl

1% CuO

 

Red

47% AP

32% SrN

15% Resinox

5% MgAl

1% Fe2O3

Orange

 

52% AP

20% SrN

15% Resinox

7% BN

5% MgAl

1% Fe2O3

 

We put some of these on the Acme Thrust stand last week at WWB... interesting results.

 

 

Seymour,

 

On your BP rockets (60BP, 30Flash, 10MgAl, 2Wax) do you ram or press these?

What kind of solvent do you use to mix the Wax into the mix with?

What pressures do you press the rockets to?

 

Tried one of these too...

 

[Seymour]

Nice to see some actual Data!

 

What were the other details of the motors, like core length, choke diameter. I assume the second one was nozzleless?

[ddewees]

core length is 6.833", choke is 0.5"... and yes, second one was nozzleless.

 

I haven't tried using a nozzle on the second formula, but I plan to within the next month or so.

 

 

We (Maserface) actually brought the thrust stand back to Utah/Idaho... so I (we) plan to do a lot more testing and I'll try to post the results here.

 

 

I'm thinking about using an 8" core length with everything else the same. Both fuels don't seem to perform very well once they get above the spindle.

 

 

The first graph was using the yellow formula...

[ddewees]

Seymour,

 

Just received a set of custom tooling yesterday I ordered just for these rockets... and the results seem good so far.

 

I made the spindle significantly longer, and reduced the core diameter/choke.

 

This has eliminated the chuffing we were getting before, and they just burn at full thrust now.

 

Here's a picture of the tooling, and a video of the first motor built. I'll have to get these on a thrust stand... they sound like they can probably lift a decent payload now.

 

http://i1149.photobucket.com/albums/o588/SaltLakeAreaPyros/20140522_203625_zpsacfb53df.jpg