Sciencemadness Discussion Board

Composite rocket fuel...

albqbrian - 27-5-2011 at 00:29

I'm not sure how familiar you are with this so I'll write a brief intro. Two things in it's favor: it's as safe as easily made energetic material can be, and it's most likely legal for you to make and burn. The latter is no small thing. Pretty much ANY chem or mixture you can make (in the US) that explodes is illegal for one reason or another. Violations are serious Federal crimes that will bring the dreaded BATFE to your door. That you don't want. They tend to be wildly overzealous, shall we say, in their enforcement actions. Back to more pleasant things. I'm talking about what we commonly call APCP (ammonium perchlorate composite propellant). This stuff has plenty of ummph; it's what's in the Space Shuttle solid boosters.

APCP (and it's kin made with AN or PP) is a polybutadiene polymer that encapsulates the oxidizer along with various optional materials. A basic formulation is:

80% AP usually a mix of two or more particle sizes
4% to 8% Al sometimes MG
15% HTPB or other similar polymer source
2% Isocyanate curative Isonate 143L is the most commonly used
1% to 3% additives (Tepanol, lechithin) as desired

You put in the polymer and start mixing. A metal bowl is fine. I do it on a hot plate as the stuff has the viscosity of honey at RT. Mix in the metal. Mix in the AP. I do all this outside, well away from anything that a large, 5000 deg flame might harm. Depending on the batch size I use either a Kitchen Aid mixer or a 20qt Hobart. After it's all mixed you add the curative and the clock starts ticking. With the 143L that's about 30 to 40 minutes. For larger batches I use a mix of two curatives to get acceptable pot life.

After it's mixed you cast your mixture into fuel grains. Here there is endless variety. This is why I love the stuff. I can make all different size motors; from 1/2 in to 12 in, colors, smokes, sparks, grain designs (straight core, star) etc. I find 1 and 1.5 inch PVC tubes are good beginner sizes. Their couplers hold them upright while I push in the wet mixture.

After a couple of days you pull out your coring rod and you have a fuel grain. Now you construct a useable motor. That is harder than making the fuel. But endlessly intriguing. I use shop tools, kitchen implements, common and uncommon materials, etc. You need to figure out, or make, your igniters. And on and on.

Then there's the testing. You can start simple, just a hole in the ground (the hole is a simple way to catch any inadvertent shrapnel) to see if it fires. You can video it. From the time of burn you can figure out lots. You can go further and set up instrumentation to accurately capture thrust and chamber pressure.

And best of all; you can put these suckers in a rocket and fly that baby thousands (or tens of thousands in some cases) feet in the air. This is now the area of High Power Rocketry. It is under the control of two national organizations: Tripoli and the National Association of Rocketry (NAR). www.tripoli.org www.nar.org
Most states have several clubs that do this.

The reason it's legal to do this? Those two organizations (with member contributions) fought a nearly 10 yr legal battle against the BATFE. And won!! The BATFE had classified the APCP as a low explosive. Wrong, but these agencies live to regulate. This restricted sale, shipping, forced us to get Low Explosive User permits, get fingerprinted, background checked, etc. But the stuff doesn't explode! In a motor at 500 psi it burns at all of a qtr in per sec! Our two orgs filed suit. It took about nine years and included both district court and appeals court trials. In the end the judge sided with us. The ATF has since removed all their restrictions on APCP. If you know legal things, this outcome is fairly extraordinary! It's damn near impossible to beat a Federal agency in court. If nothing else, they just drag things out and try to bankrupt you. They don't have to pay their attorneys by the hour.

So what we now have is a very interesting class of energetic material that is as safe and as legal as you'll find. My son is now 11 and wants to learn about energetics (it's genetic I guess). Unfortunately he won't be able to make the binary explosives and similar things that I did when I was his age. But the world of APCP will give him tons of options and learning opportunities. And with compounds that are fairly safe (there is NO perfectly safe energetic material) and that are legal. Given our ever stifling nanny state filled with scientifically ignorant politicians; that's as good as it will get.

I've obviously just put in highlights. If there is interest I'll be happy to supply more information, links, etc.

woelen - 27-5-2011 at 01:54

Isn't ammonium perchlorate a restricted chemical in the USA? If this is the case, then the average person cannot easily obtain this chemical and then there is no chance of being able to make an APCP composition.

But I find it a very good thing that in this case the judges chose the side of hobbyists. This indeed is a very special thing. Usually things are only restricted more and more and here we have a nice example of a relaxation.

[Edited on 27-5-11 by woelen]


[Edited on 27-5-2011 by quicksilver]

Nope, legal as can be...

albqbrian - 27-5-2011 at 07:07

No, AP is easily available, and in a variety of sizes. One supplier who ran afoul the Feds (Firefox) requires a BATF Explosives Manufacturing Permit if you buy a 55 gal drum. Less than that you're fine. Others don't have that restriction. I believe that it is restricted at some superfine stage. However the superfine stuff that is available is way more than adequate.

I had a drum a few years back. Then we moved overseas; for a two year trip to China (five and a half years later and we're still in Asia). My wife made me sell it as we were going to rent our house and she didn't want it left in our shed. Broke my heart!

quicksilver - 27-5-2011 at 13:58

Quote: Originally posted by woelen  
Isn't ammonium perchlorate a restricted chemical in the USA? If this is the case, then the average person cannot easily obtain this chemical and then there is no chance of being able to make an APCP composition.

But I find it a very good thing that in this case the judges chose the side of hobbyists. This indeed is a very special thing. Usually things are only restricted more and more and here we have a nice example of a relaxation.

[Edited on 27-5-11 by woelen]


TTBoMK - There does exist SOME restrictions on particulate size in a commercial (plant-level) medium. Several years back (I believe in Henderson NV) there was a pant explosion, the cause of which was exposure to cooper (brass coupling) under pressure of single mircon (2-9 um) particulate. Same issue in a Flare-production plant using perchlorate and NC lacquer in their product. once many oxidizer become "air-float" they appear to become problematic for production facilities that use "dry pressure" devices.

AP safety...

albqbrian - 27-5-2011 at 16:28

Yes, there is the Henderson plant thing. As noted it was an industrial scale oops involving very fine AP (1 or 2 microns) and a few million pounds of it at that. As with most disasters, it took several unlikely steps to happen for the accident to occur. It has no relevance to amateur use of AP in composite propellants. We don't use that fine of AP (the stuff we use is far larger) nor do we have the huge quantities required to get a detonation. During the litigation the AP itself was never an issue; just the fact that the BATF had classified the propellant as an explosive.

The AP used in APCP propellants ranges from 400 to 90 microns; mostly the 400 to 200 is used. These are as safe as any decent oxidizer can be. If you think of the dangers inherent in flash powders and such; it's because the ingredients are dry. Here you process the AP and the metal (if used) separately into a wet, goopy matrix. Does that make it 100% safe? No, of course not; there is no such guarantee. But it comes real close with materials any amateur can easily (and legally) obtain.

quicksilver - 28-5-2011 at 05:23

I don't mean to step off track here but I'm getting off topic all too quickly. However this issue is interesting.
In Europe smokeless powder (canister level) is marked explosive. In the USA we deal with the DOT issues by marking smokeless as a "propellant" and BP as explosive. - That always appeared too transparent. yet no one has ever really given a damn. Dry combustibles can come very close to extreme danger in transportation; especially in rail systems where the possibility of air/fuel catastrophe looms large.

edit:
I suppose it wasn't that big of a OT remark :P

[Edited on 28-5-2011 by quicksilver]

OK i"m confused...

albqbrian - 28-5-2011 at 14:26

What's your point and how does it relate to my APCP overview. I was stressing that we have a very versatile, fun, safe, and legal energetic material available. You seem entirely focused on the AP.

Can you elaborate your position?

gregkdc - 28-5-2011 at 17:15

I don't mean to pee on your parade about APCP being completely legal, but it is almost always in violation of local codes. How can this be? True it is leagl federally due to the lawsuit with the BATFE but most cities and several states have adopted the international fire code which then references the the NFPA codes. In short the majority of people will find that they live in a place where it is still illegal. If you haven't read the NFPA codes I suggest you do, you can find them here.

http://www.nfpa.org/index.asp?cookie_test=1

You will have to register to read the codes and you will want to read codes 1127 and 1122. Code 1125 is somewhat relevant and details the manufacture of rocket motors but is specifically for commercial manufacturers and not the individual.

I have brought this up with my Tripoli prefect and all I am getting are somewhat delusional responses as to why it is still legal. I have asked the state fire-marshal and his office wasn't able to give me an answer. Last Ben Russel the main guy over research launches for Tripoli wont return my emails. I wish that we could get this straightened out but as of right now I can't even get an honest discussion started.

The implications of this are not only can you be fined jailed or harassed for research rocketry if there ever was an accident or property damage at a launch this would most certainly void the insurance coverage of the launch. I would like to see a change or modification of the NFPA codes so that it has a line or sub-clause that allows for certified users to make motors. After all this would be congruent with current practices in rocketry.

P.S. For all other people reading this if you are making energetic compounds you should also read the NFPA code 495 detailing explosives including binaries and precursor chemicals it was even worse then I thought.

Hmmm...

albqbrian - 29-5-2011 at 07:48

I thought the NFPA was more oriented to commercial manufacture, but admittedly I'm not current on those regs. And I certainly understand it's not what I think they are about.

But I have a good source here so I'll check and report back.

I'm friends with Terry McCreary. He's the current Tripoli President, a university chemistry prof, and has written our "bible" on amateur APCP manufactue. He should know what is what with the NFPA regs. I'll drop him a line.

gregkdc - 29-5-2011 at 09:30

Great! I look forward to what you can come with. I applaud tripoli for allowing research rocketry and would really like to get this straightened out. In particular could you have him explain the legal justification for allowing research rocketry where the NFPA guidelines have been adopted as law? It just so happens that I live in such a State.

Guidelines 1122 and 1127 specifically say that it is prohibited for a person make, use, ignite etc. a non certified motor. One possible way around this is if you have the expressed permission from the local authority having jurisdiction (AHJ) for short for example the local fire department. However the local fire department will use the NFPA guidelines to base their decision and would not have agreed to allow research motors. If there was an incidence during a research launch, or at home making the motors, Tripoli or the individual would be liable for the damages, not to mention that they would be in violation of local laws. You can imagine how this could get real messy.

As I said in my previous post it would be ideal to get a line or sub-clause added to the code to specifically exempt certified users but as it stands now it isn't clear. Not to mention after talking to my local prefect I doubt the local AHJ has been properly informed. Please let me know what you come up with. Thanks Greg

gregkdc - 12-6-2011 at 07:53

Any word form Terry yet, the suspense is killing me? I have a heap of AP waiting to be mixed up but I won't make any until I can get a straight answer. I also know that if I were to get advice form the authorities, attorneys etc that are not pro-research that they will likely conclude a no go. So to have the advice of someone like Terry would be priceless. Thanks Greg

Not conclusive...

albqbrian - 12-6-2011 at 15:02

Terry is a busy guy now. He said we both had good points. The ATF ruling made it much simpler to buy, store, and use propellant. But as you pointed out, as one descends into the local morass there are no certainties. Certainly nothing like the clear ruling that BATF got so deservingly bashed upside the head with.

I'm going to keep looking into this. In particular I'm interested to see how NFPA stuff gets put into law. I mean, they are not a legislative nor regulatory body. They are a self appointed group of industry types. My bro is both a law and engineering (yes he is a weird thing) professor. I'll put him onto this when he gets off vacation.

Where do you live? What sort of "clearance" are you looking for in order to make AP? Are you positive that you're bound by NFPA, etc.?

gregkdc - 12-6-2011 at 17:29

I don't really know what to expect from all of this. I suspect that TRA feels like it is too big of a hassle to deal with all of the local codes. I live in one of the states that have adopted the NFPA standards as law. Here is another discussion I found about this subject that lists more states. I don" know how accurate the info is but it is correct for the one I live in. I don't want to say what state exactly because it will become clear as to what club I fly with and I don't want to drag my local club members into this.
http://www.electronicspoint.com/states-have-adopted-nfpa-112...
The reality is that their are TRA members all over the country in violation of local laws and they have no clue that they are opening themselves and Tripoli to litigation and lawsuits.
The easiest way to get this fixed would be to simply write a waiver or sub-clause into the 1127 codes that exempts level 2 members. I think this is a long shot though because as you mentioned NFPA is mostly industry people that have a vested interest in people buying motors from them. I never liked the self righteous BS that Estes has promoted all of these years. I buy a pack of motors for $9.00 and I can make the same motors for .50 cents come on.
Obviously TRA wouldn't have research rocketry in the first place if they didn't support these types of activities, but this is going to get ugly fast if there is an incidence.
The question is who will be responsible for any damages, fines etc. if there is an accident. Will Tripoli throw it's own member under the bus and say we only support activities that are legal therefore the insurance is void and you are on your own? All the while the local prefect said it is legal and is hosting research launches under TRA, maybe he will be the one who is responsible? Does the local AHJ know that the rocket club is flying motors that are in clear violation of the code that was agreed on to gain permission to fly? They could grant the permission needed to fly research motors but then what about making the motors?
So many questions need to be answered and fast. This situation is a ticking time bomb. I like what Tripoli is doing but I don't like how this has been handled. They have left themselves and their members open to potential liability. There is the hopeful possibility that I am wrong, but the fact that nobody can answer this question is disheartening.

Vijay - 2-3-2015 at 02:23

Hey!

Do any of you have a reference for the formulations you've put up? Say,
"80% AP usually a mix of two or more particle sizes
4% to 8% Al sometimes MG
15% HTPB or other similar polymer source
2% Isocyanate curative Isonate 143L is the most commonly used
1% to 3% additives (Tepanol, lechithin) as desired"

Please help me out!

roXefeller - 2-3-2015 at 15:12

What fuels have you shot already? Not necessarily a bound composite.