AP can detonate despite what all of us think.

Hello again KT,
I had a discussion with someone who really knows their stuff and in actuality you do have a point but it is limited. Don't flame me folks but I've been told
that there are some very energetic grades of APCP that the MILITARY uses that under the right conditions can be made to detonate. I've also been told that no hobby vendor or Ex'er for that matter can or would be able to safely go there. The additives that are used are close to unobtainium and making the stuff is downright very dangerous. It has been duly documented that our usual grades of APCP one can buy or make cannot detonate and we still have grounds to press for relief through the courts. Donate through either Tripoli or NAR please. A casual modeler shouldn't have to jump through a bunch of hoops to keep a few K grains or whatever around.
Kurt
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A lot of confusion here, but I'll take a whack at clearing it up. Yes, APCP can detonate. This is not news. All of the ballistic missiles launched from submarines can detonate or are shock sensitive. The reason is that nitroglycerin is added to the propellant to up the specific impulse. The launch tubes make the missile volume limit so maximum specific impulse is required for the desired range. These types of AP propellants are called "Double Base". Some types of APCP propellants use an energetic binder that can make the propellant shock sensitive and detonate. Often an energetic plasticizer is added to not only "thin out the mix viscosity", but to increase the specific impulse and/or burn rate. These energetic plasticizers, even with an inert binder, can make the propellant shock sensitive. All of the propellant types above are used by the military, not in hobby rocket motors.
Your video was of an AP factory blowing up. AP by itself is shock sensitive. It becomes more sensitive as the AP particle is decreased. 90 micron AP is the smallest particle sized shipped under DOT regulations, Small AP particles are too dangerous for transportation on public highways or railroads. Simply dropping a drum full of very small AP particles can cause the drum to detonate. Again, this is well known to users of AP as the AP MSDS sheets discusses all of this. In industry, a simple bimodal mix of AP particle sizes is 10 to 1. 200 micron AP is bought and then it is ground down to 20 microns to get the 10 to 1 ratio. This is done remotely as it is not unusual for a grind station to blow up during this process of grinding.
Ok, how can it be that AP which is shock sensitive by itself, (i.e., can be made to detonate by hitting it with a hammer) be put into a propellant and not have it be shock sensitive. The answer is the binder. In very simple terms, it is like a "rubber cushion" around each particle and provides a barrier or shock dampener to a detonation wave from getting started in the propellant. The effectiveness of the binder in making the propellant non-detonable is measured using a "card gap test". Again, in simple terms, a sample of APCP propellant is impacted by a projectile fired at a known kinetic energy. Cards are placed between the projectile and propellant sample such that the projectile loses kinetic energy as it passes through the cards. The first test would be with zero cards. If the projectile does not cause the propellant to detonate, then the propellant is considered non-detonable and extremely safe. This is the case for hobby propellant. If the propellant detonates, then cards are added until the projectile loses sufficient energy as it passes through the cards such that the propellant does not detonate upon impact. This is the card rating of the propellant. Based on the rating, the propellant is classified as the 1.1 (detonable) or 1.3 (non-detonable propellant). The dividing line is 70 cards or (70 kbar input shock pressure). What that means is that propellants 70 cards and under are considered 1.3 propellants or non-detonable. However, as we just discussed a 30 card, 10 card and 50 card APCP will detonate even though they are rated non-detonable. But, hobby propellant is rated as 0 cards, which means it has not detonated under the tests, not even once.
Finally, the 60 inch rule of APCPs detonating. I have heard this, too. However, I can not find anything to back it up. Once you understand the mechanics of what is going on, it makes even less sense. What is really being discussed here is the distance required to set up a detonation wave. For example, ammonium nitrate or AN by itself has a detonation wave distance of about 8 inches. That means it takes a solid particle of AN 8 inches thick to just start the detonation wave, assuming sufficient impact force has been imparted to cause detonation. I can easily envision an APCP formulation that could set up a detonation wave in one inch, 20 inches, 50 inches, 60 inches, 130 inches or take your pick. It would depend on the formulation, particle sizes, etc. The bottom line is that there is no rule of thumb of 60 inches for all APCP formulations. I could easily make an APCP formulation that could be 500 ft long and you will not get it to detonate.
This has been long winded, but perhaps the differences between one APCP and another APCP begin to come through. There is no one APCP fits all or rules of thumb. The problem is the ATFE has decided one APCP does fit all and they picked the APCP that detonates as the one that fits all. The injustice is that the hobby APCP does not detonate. So, the TRA/NAR suit's complaint against the ATFE is accurate and not a waste of time. If the ATFE was really interested in correcting this injustice rather than just trying to save face, they would more exactly define which APCP are on the explosives list. This could easily be done by the number of cards in the card gap test. They would not have to accept 70 cards. They could use a lower number or make it zero cards. I proposed this approach to them, but received no reply.
John Wickman
snipped-for-privacy@pacbell.net wrote:

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John Wickman wrote:

A footnote that I should have added to reduce some possible confusion on card gap testing. The card gap test I described is an old one we used at Aerojet over 30 years ago. Current procedure is to use an explosive charge to generate a known pressure wave propagating through a gap filled with cards or just a gap of so many card thicknesses between the explosive and sample. I believe more sophisticated methods are being developed to just provide known shock pressure. The method of testing does not change the message above.
John Wickman
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John Wickman wrote:

So now you're saying I have to take the nitroglycerin out of my apcp? Where will all this end? ;-)
Chuck
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Chuck Rudy wrote:

Well, you could put it in the ejection charge. Just watch out for lawn darts. ;-)
John
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John is refering to PEG/NG (polyethylene glycol) cross-linked, double base propellant. NEPE-75 is a common trade name. It's origins go back to the 70's and even before.
Anthony J. Cesaroni President/CEO Cesaroni Technology/Cesaroni Aerospace http://www.cesaronitech.com / (941) 360-3100 x101 Sarasota (905) 887-2370 x222 Toronto

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Anthony Cesaroni wrote:

Anthony
You're giving away all the secrets. But the education is well worth it. ;-)
Chuck
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Anthony Cesaroni wrote:

Anthony
Thanks for the tip, here's my last go at that 'contaminated' apcp.....
http://www.youtube.com/watch?v=mnmIe6SQX9s
perhaps I'll now have regular lawn darts. ;-)
Chuck
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The demonstrated zero card DDT length for classical APCP is as low as 9 centimeters but as high as 100. Devenais references SNPE tests if you need to look it up. The DOD recently asked DOT to conduct wide area card gap testing on any APCP motor over 6" in diameter.
Anthony J. Cesaroni President/CEO Cesaroni Technology/Cesaroni Aerospace http://www.cesaronitech.com / (941) 360-3100 x101 Sarasota (905) 887-2370 x222 Toronto
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I seem to recall some old Aerojet AP/PBAN formulations that could not be made to detonate at even 60 inches, which would be well beyond 100 centimeters. I guess that would be about 152 centimeters. (I'm not a metric guy.) The data might be in the DTIC database.
John
Anthony Cesaroni wrote:

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Detonation and failure of the motor casing are two very different things.
I can overpressurize a tank with steam and have it catastrophically fail, taking most of the building with it. This doesn't mean steam can detonate.
On Nov 17, 12:30 pm, snipped-for-privacy@pacbell.net wrote:

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