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Hennig Brand
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I was just about to do what was traditional and lower the flame temperature by going with a lower NG content double base or even single base
propellant. However, high NG double base propellants have many advantages, just one of which is higher performance. One of the big advantages is that
only about 12.6%N nitrocellulose is needed to produce double base propellants, whereas about 13.4%N guncotton is needed to produce high performance
single base propellants which is more difficult to synthesis. It really would be great to find an additive, or component for a triple base, that would
allow high NG content propellants to be used and still have acceptable barrel life.
[Edited on 5-2-2015 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Trotsky
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I've read that NC is soluble in ethanol up to about 11.8% N content. Is NC with high N content also insoluble in acetone, or does it retain
solubility in acetone regardless of N content?
Is there a (nondestructive, preferably) way for the amateur to determine rough N content of NC?
Inspired by Hennig's posts I have been experimenting with home made NC powder for use in 12g shotshells. I have no experience reloading bullets, but
I've spent hundreds of hours reloading shotshells, primarily 12 and 20g. I have gotten to the point of testing my powder in "blank" shotshells, just
to determine the 'feel' relative to my usual load for clays (which I also made up some blanks of). I thought that for the amateur enthusiast a
shotgun would be somewhat more forgiving than a rifle since less pressure is generated. My first trials weren't satisfactory, unsurprisingly, and I'm
looking for a way to determine N content of the NC used from batch to batch for obvious reasons. I'm currently working on four batches, of which half
is being nitrated under one set of conditions, and the other two under another, not so much to determine which conditions give me the best result, but
to see how much variation I get between seemingly identical conditions. They're all smallish 15g batches, though.
Hennig, maybe you already discussed this somewhere, but what is your source of cellulose for nitration? I've been using washed cotton balls and it
seems like a lot of material is lost as fines when neutralizing the acid and washing it. I thought washing it before hand, so I wouldn't be wasting
nitration bath on fines I was going to lose anyway, would help eliminate that, but it still seems to be happening, though not quite as badly. I don't
really want to try draining the liquids through a filter, since it's slow and I wash and neutralize many times before calling it good.
Trotsky
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Hennig Brand
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Celluloid cotton (ca. 10.5 - 11 %N) and gun cotton (ca. 13.0 - 13.6 %N) and everything in between is soluble in acetone. I just recently posted a good
pdf as an attachment to a post earlier in this thread which will answer a lot of your questions.
http://www.sciencemadness.org/talk/viewthread.php?tid=22649&...
Apparently there are other methods for determining N content, other than a nitrometer, such as titration methods. I haven't tried them yet though. And
I guess these are also destructive methods, which is not what you were looking for. If you don't lose very much material during nitration and washing
the difference in weight, before nitration and after, can be used to calculate an approximate nitrogen content.
Shotguns do operate at much lower pressures than rifles you are right. The only thing about shotgun testing is that there is little warning between
shots that the pressure is getting too high. It is definitely possible to split a shotgun barrel. With a rifle cartridge the bolt can get sticky,
primers can flatten out, casings swell, etc, as pressures get higher than they should be which can serve as a warning as propellant load is increased.
At first I was using cotton balls, but lately I have been hydrolyzing cotton balls to make microcrystalline cellulose. When nitrating cotton balls I
noticed a small amount of fines being lost during washing, but very little the last few times (ca. 0.1-0.2g for 10g batch). I think the amount of
fines (fiber length) has a lot to do with the particular cotton source used and on the processes used as well.
[Edited on 5-2-2015 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Hennig Brand
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Stability Testing, Bergmann-Junk-Siebert-Test
I found this Los Alamos handout the other day which describes stability testing of explosives including NC. After reading about this from a few
different sources, I do not think that this type of stability testing would really be all that difficult for the amateur. I think standard brewing
airlocks could be used. Temperature control would be the only real technical issue, unless one had the proper equipment.
The reactions of interest if using the Siebert method and H2O2:
3NO2 + H2O <----> 2HNO3 + NO
2NO + HNO3 + H2O ----> 3HNO2
HNO2 + H2O2 ----> HNO3 + H2O
Attachment: Explosives Science - Information on NC Stability Testing.pdf (1.6MB)
This file has been downloaded 1132 times
Attachment: Bergman Junk Test Apparatus.pdf (85kB)
This file has been downloaded 1954 times
 
[Edited on 5-2-2015 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Bert
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Threads Merged
5-2-2015 at 08:28 |
Bert
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As a reference, National Center For Forensics: Smokeless powder database
Information on constituents and physical characteristics of various commercial propellants.
http://www.ilrc.ucf.edu/powders/search.php?resultPageSize=50...
No % given, only constituents. NC is assumed, NG and other ingredients are called out.
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Hennig Brand
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Here is another good article on smokeless propellant stability testing and stabilization and also a good picture and description of a commercial
Bergmann-Junk testing apparatus.
Attachment: Testing the Chemical Stability of Smokeless Propellants.pdf (746kB)
This file has been downloaded 2733 times
Attachment: Nitrocellulose Stability Testing Bergmann-Junk.pdf (103kB)
This file has been downloaded 1162 times
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Bert
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Thanks franklyn! This is interesting looking-
http://www.dtic.mil/dtic/tr/fulltext/u2/595292.pdf
Rapopart’s Rules for critical commentary:
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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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franklyn
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whoops ships in the night again
Here it is again, updated post
http://www.sciencemadness.org/talk/viewthread.php?tid=1987&a...
http://www.sciencemadness.org/talk/viewthread.php?tid=8144&a...
Compounds of High Nitrogen Content in Propellant Compositions
www.dtic.mil/dtic/tr/fulltext/u2/595292.pdf
Dinitrobiuret & its Salts .pdf
http://www.sciencemadness.org/talk/files.php?pid=189115&...
Attachment: Dinitrobiuret - New Research Energetic Materials 2004.pdf (1.5MB)
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Attachment: Dinitrobiuret DNB thermal decomp.pdf (334kB)
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http://www.sciencemadness.org/talk/viewthread.php?tid=14033#...
Biuret from Urea .pdf
http://www.sciencemadness.org/talk/files.php?pid=189115&...
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Pasrules
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-Tetraazide-
Interesting how a double ligand can provide such amazing stability
http://en.m.wikipedia.org/wiki/Silicon_tetraazide
Atropine, Bicarb, Calcium.
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Hennig Brand
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Attached is a report done by the Australian military. A mathematical model was created which takes into account chemical erosion, thermal erosion and
mechanical erosion and allows comparisons to be made between different propellants. It is interesting that the propellants with the highest flame
temperature are not necessarily the propellants which cause the most barrel erosion for a given muzzle velocity.
Attachment: Understanding and Predicting Gun Barrel Erosion.pdf (511kB)
This file has been downloaded 1275 times
DNT could be used as an additive to lower flame temperature, slow burn rate and reduce barrel erosion. DNT is something that has been used in North
America for this purpose and it is fairly easy for the amateur to make. I have seen single and double base formulations that included DNT.
[Edited on 6-2-2015 by Hennig Brand]
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Trotsky
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Quote: Originally posted by Hennig Brand  | Celluloid cotton (ca. 10.5 - 11 %N) and gun cotton (ca. 13.0 - 13.6 %N) and everything in between is soluble in acetone. I just recently posted a good
pdf as an attachment to a post earlier in this thread which will answer a lot of your questions.
http://www.sciencemadness.org/talk/viewthread.php?tid=22649&...
Apparently there are other methods for determining N content, other than a nitrometer, such as titration methods. I haven't tried them yet though. And
I guess these are also destructive methods, which is not what you were looking for. If you don't lose very much material during nitration and washing
the difference in weight, before nitration and after, can be used to calculate an approximate nitrogen content.
Shotguns do operate at much lower pressures than rifles you are right. The only thing about shotgun testing is that there is little warning between
shots that the pressure is getting too high. It is definitely possible to split a shotgun barrel. With a rifle cartridge the bolt can get sticky,
primers can flatten out, casings swell, etc, as pressures get higher than they should be which can serve as a warning as propellant load is increased.
At first I was using cotton balls, but lately I have been hydrolyzing cotton balls to make microcrystalline cellulose. When nitrating cotton balls I
noticed a small amount of fines being lost during washing, but very little the last few times (ca. 0.1-0.2g for 10g batch). I think the amount of
fines (fiber length) has a lot to do with the particular cotton source used and on the processes used as well.
[Edited on 5-2-2015 by Hennig Brand] |
I was going to measure the difference in weight, so I was very carefully rinsing the cotton balls neutralizing them. I had gotten them completely
white (I am using drain cleaner sulfuric acid, and with the AN added, the bath turns a pinkish color, which the balls hold until they're well rinsed).
The only time I've ever had a 'runaway' NC reaction was when rinsing the cotton, and as the sulfuric acid would get hot from the sudden addition of
water, occasionally a hotspot would develop causing a sudden eruption of red gas. Anyway, I determined they were all white, and cold, so I figured
I'd squeeze them out and place them in my bicarbonate solution. However, as I squeezed them a substantial part of it started burning! Very slowly,
as it was wet, but wow... talk about unexpected! I'd hate to imagine what would happen if it had all gone up- 15g in my hand would be no good! I
had allowed these to soak in the nitration bath for about 50 hours (I usually do 24, but work got in the way this time), perhaps that batch of NC was
highly nitrated?
Not only do shotguns develop lower pressure, when firing blanks it'd be pretty hard to develop enough to split the barrel, unless it were to actually
detonate, I think. I haven't gotten to firing a shell with shot loaded into it yet, but I'm looking forward to it.
The powder I've always used was in the form of disc-shaped flakes. I was thinking of making something is used for extruding pasta or play-do, but
with tiny holes. I would then press through just enough for one flake through each hole, and run a blade across, cutting a couple dozen flakes per
pass. It'd be slow going at first, but once I'm satisfied with what I'm getting, it won't be hard to automate it somewhat. I've sort of started,
actually. I have a piece of pipe with a flat sheet of metal welted to the end that I drilled 10 small holes through. The other end is threaded on
the outside, and I have a cap that screws onto it. In the center of that cap I drilled a hole and welded a 3/4" nut over that hole. I have a length
of threaded rod that I can turn into that nut, and on the end of that rod is welded a 1/4" stainless circle cut to fit the pipe very carefully. It's
a snug fit, so it's hard to get it in at first, it's gotta be very straight. I'm looking for a way to loosen that up a bit and have a bit of rubber
or something around the edges to make for a better seal. I just made it yesterday so I haven't had a chance to try it out yet, but my plan is to
determine how far to turn the threaded rod to extrude just enough material to make a flake of the proper thickness. I think that as it is it's going
to be too hard to control like that unless I have a really long handle and have a dial of some sort with markings for each point to turn it to.
The idea was to have a razor blade cut the flakes as they're made automatically, but I haven't worked out how I want that to work. I was thinking of
using an electric motor, but I seems like it'd be hard to mount. Instead I'm thinking know that I'll come up with a way to have a sort of guillotine
chop, I know how I'll rig that up and it'll be sturdier than a spinning blade, liable to be bumped and knocked out of the perfect position necessary.
Sorry for the long post, I spent a lot of time working on this last night and I'm hopeful that it'll work. And if it doesn't, oh well, there's
nothing fancy or complicated about it, and it cost me less than twenty bucks to make (I'm guessing, I had most of the stuff lying around), but it
should give me the ability to regulate the grain size with far more precision if it does. That'll make me a lot more comfortable firing full loads.
I'm looking forward to taking my first rabbit with home made powder (maybe I'll make some shot, too. just about the only thing I can't really make is
the shell itself and the primer).
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Bert
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| Quote: |
The only time I've ever had a 'runaway' NC reaction was when rinsing the cotton, and as the sulfuric acid would get hot from the sudden addition of
water, occasionally a hotspot would develop causing a sudden eruption of red gas. Anyway, I determined they were all white, and cold, so I figured I'd
squeeze them out and place them in my bicarbonate solution. However, as I squeezed them a substantial part of it started burning!
|
In NC plants, removing spent acid was done in a centrifugal wringer- A spinning mesh basket, similar to a washing machine drum on "extract". They
caught fire fairly often...
Wringing and Drowning Theory
| Quote: |
It has been experimentally demonstrated that a 20 pound high grade linters dipping pot charge may be safely wrung as long as the acid retention
is never reduced below 0.7 pounds of total acid (HNO3 ± H2SO4 ± H20) per pound of nitrocellulose.
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Remove too much of the spent nitrating mixture before drowning the charge in water, you may have a fire.
I must tell you, your assumption of greater safety in using a shotgun for testing is just that- an assumption. Plenty of shotguns were destroyed in
the early days of smokeless and semi smokeless powder development. We have better metallurgy for the most part now, but I would not be assuming
ANYTHING (or holding a test gun in my hands).
I have a dead tree copy of this- It is from the early development period, and mentions slight changes in powder manufacture leading to damages. Don't
have time to dig out page # & exact quotes right now.
http://archive.org/stream/gunitsdevelopmen00greerich/gunitsd...
In addition to cut or punched "flakes", early "bulk" shotgun powders were sometimes made by tumbling the chopped NC fibers (& sometimes other
powdered ingredients) in a revolving "sweetie drum" and spraying the tumbling NC fibers lightly with a solvent that could gelatinize the NC.
Eventually, the solvent droplets would stick fibers together into little clumps, and they would end up with a bunch of what looked like fuzzy tiny
snowballs of NC fibers stuck together. For even faster burning (blank powder), a waterborne adhesive that did not gelatinize the NC at all could be
used with very high % NC.
These powders were designed to be loaded with the same size scoop or whatever other volume measures had been used with black powder shotgun shells,
rather than by weight, hence the name "bulk powder". They were low density, not very durable in handling, and tended to be very fast burning- These
absolutely DID damage guns with fairly minor changes in % Nitrogen of the NC used.
Historical interest only, unless you want to duplicate "EC blank powder", perhaps. Note that the grenade fuze shown below with the smokeless powder
filler has no blasting cap, but instead a black powder igniter charge. Loaded behind a projectile, it may turn a gun into a grenade.
| Quote: |
To fully develop the MK II into what most of us know today, another step was necessary. In the Basic Field Manual , Volume III, Chapter 5, Instruction
With Hand and Rifle Grenades, 1932, a new grenade was described In this item the body remained the same with 40 deep serration's (48 counting the fuze
neck), a filler plug with the body painted yellow and the main bursting charge consisting of .74 ounce of E.C. blank fire smokeless powder. The
designation of E.C. indicated the proprietary compound first made by The Explosive Company seen in blank rifle cartridges.
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Hatcher's Notebook: Notes On Gunpowder
https://books.google.com/books?id=yESNUKSg5aMC&pg=PA314&...
[Edited on 7-2-2015 by Bert]
[Edited on 7-2-2015 by Bert]
Rapopart’s Rules for critical commentary:
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3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Hennig Brand
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The nitration of cellulose is an equilibrium reaction, so to prevent loss of nitrogen content the acid on the NC needs to be diluted as quickly as
possible. I use a large beaker of very cold water into which the NC, one cotton ball sized piece at a time, is plunged and agitate very vigorously
with a glass stirring rod. The acid needs to be diluted as quickly as possible. This prevents hot spots and oxidation from the heat of dilution from
occurring and also prevents any significant loss of nitrogen from occurring due to a partial reversal of the esterification reaction.
Interesting, good luck with your project. I was doing some thinking last night as well about how to make more regular propellant grains and I came up
with a few ideas. If you look at the microscope pictures I took of my propellant, the flakes are very irregular. I was thinking of using moulds of
known area that the propellant could be poured into before the solvent was evaporated. For a given mass of propellant this would be a more precise way
of controlling flake thickness than trying to control viscosity by adjusting the amount of solvent. After most of the solvent had evaporated a cutter,
much like a cookie cutter, with many parallel blades could be pressed down onto the sheet of propellant which would cut it into even strips. The
cutter would simply need to be turned 90 degrees and the strips cut crosswise to make perfect flakes. If it took a lot of force, such as if a big
sheet of propellant and large cutter were used, a press could be used to force the cutter through the propellant sheet.
[Edited on 6-2-2015 by Hennig Brand]
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Bert
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For your consideration:
Fred Olsen's MIT Bachelor's thesis: On the Gelation of Nitrocellulose
(see an overview of the graining process p. 55. How it was done, lots of nice little tech details)
https://dspace.mit.edu/bitstream/handle/1721.1/72784/3476445...
The historic rolling, punching, cutting & extrusion methods certainly work, and they are still used today for many products. I suspect they are
made on some very durable legacy equipment, possibly older than many of the people running the presses.
Ball or flattened ball powders are very popular since the 1930's...
I am very lazy, and kind of like the idea of using a magnetic stirring hot plate and a beaker to try a small batch? So much less equipment to
fabricate/bodge up. With Fred's description of using various electrolytes in the liquid to control droplet size, one might even get grains of a
desired size to form themselves, after a bit of practice.
Solvents used could be ethyl acetate and water, for a first try. KleenStrip sold technical ethyl acetate as "MEK replacement" until last year, I have
seen it on the shelves in some stores as recently as last month.
Afterwards, maybe one could run the grains through a warm roller to flatten if it seems necessary to even out or speed up burn.
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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Bert
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Deterrant coating method for STRANDS of triple based powder, where a water bath application would leach out the water soluble nitroguanidine-
Typicaly, strands coated before chopping into grains, and central core of resulting tubular grains NOT coated. The description of prior art in
deterrant coatings, solvents etc. is of interest.
http://patentimages.storage.googleapis.com/pdfs/US4300961.pd...
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Hennig Brand
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Interesting finds, thanks. I am kind of interested in using DNT as a deterrent coating now.
I have seen the following propellants overview page many times before as it often comes up when doing Google searches of propellants and such. I
decided to make a pdf of it and attach it here, since it has a lot of good information about advances in gun propellant technology during the first
half of last century.
http://www.navweaps.com/index_tech/tech-100.htm
Attachment: Naval Propellants - A Brief Overview.pdf (196kB)
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PHILOU Zrealone
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H2N-NH-CO-N=N-CO-NH-NH2 is a good idea!
One step further ...
Polymeric (-NH-NH-CO-)n (poly-carbonyl-hydrazin) would not be bad too... just as the oxydized version (-N=N-CO-)n (poly diazo-carbonyle).
In a way to increase density further oxalyl variant (-NH-NH-CO-CO-)n and (-N=N-CO-CO-)n.
PH Z (PHILOU Zrealone)
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Bert
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Thanks for the suggestions, PHILOU-
You generally need a solvent for applying these, I have read that DMSO dissolves azodicarbonamide, and that it will precipitate from DMSO solution on
contact with water.
I ASSUME DMSO would carry the substance past the surface of the grains and into the interior as well, depending on dwell time before contacting a
water rinse.
Can you suggest solvents for your proposed materials?
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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Bert
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Does anyone want this thread stickied?
And maybe change of title to "propellants and powders: single, double and triple base"
Or suggest any other suitable titles?
Rapopart’s Rules for critical commentary:
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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Hennig Brand
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I think it should be stickied. It is turning into a great thread.
The following copy/paste is from, "High Energy Materials: Propellants, Explosives and Pyrotechnics" by Jai Prakash Agrawal (pg. 227). Notice how DNT
is listed as a propellant coolant as well as a surface moderant.
"4.8
Ingredients of Gun Propellants
The gun propellant formulation usually contains one or more energetic compounds
as main ingredients. In addition, it includes minor quantities of plasticizer,
stabilizer, inorganic salt, surface moderant, ignition improving agent, flash
reducing agent, decoppering agent, gun wear reducing agent etc. Some important
ingredients are:
• Energetic compounds: NC, NG, picrite, RDX etc.
• Plasticizers: phthalate esters (DEP, DBP, DOP), TA, NG, liquid nitro/azido
compounds etc.
• Stabilizers: DPA, carbamite, methyl centralite, 2NDPA etc.
• Coolants: dinitrotoluene (DNT), TNT, carbamite, mineral jelly etc.
• Flash reducing agents: K2SO4, cryolite, potassium nitrate etc.
• Inorganic salts: CaCO3 . MgO etc.
• Ignition improvement compounds: Ba(NO3)2 , KNO3 , camphor, carbon
black etc.
• Surface moderants: carbamite, camphor, DNT, methyl centralite etc."
There are other texts too giving similar descriptions for how DNT is used in propellants. Some texts list DNT as a propellant plasticizer as well. It
would seem that DNT can be incorporated into the main propellant mixture, not just on the surface as a deterrent but, also for the purposes of cooling
the propellant and as a plasticizer. It seems like DNT has had extensive use for these purposes.
Quite a few materials seem to be effective for cooling a propellant, even inert materials, however nitroguanidine would likely be very effective at
cooling and sacrifice less in performance than most, or all, of the other choices. Nitroguanidine would usually win in terms of nitrogen production,
as well, which is another big advantage for reducing barrel erosion. Personally I hope to find that DNT works reasonably well and helps make
serviceable rifle propellants. Obtaining cutting edge performance with expensive/exotic materials is probably not where I am at in my quest for
homemade propellants. Being able to use readily available or easily made materials is very exciting though.
[Edited on 8-2-2015 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Bert
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Mood: " I think we are all going to die. I think that love is an illusion. We are flawed, my darling".
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And FedEx will ship 2,4 DNT to me (ground freight only). Thank you, FedEx...
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Hennig Brand
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The following was taken from "TM 9-1900, Ammunition, General" 1942 edition (pg. 33). The way it is stated is a bit open to interpretation, but it
looks as though perforations were considered of much less importance for cylindrical small arms propellants (.30 cal. for example) than for
cylindrical propellant for large guns.
"17. SMOKELESS POWDER.
a. Characteristics: Smokeless powder is essentially gelatinized
nitrocellulose and is manufactured in the form of flakes, strips, pellets,
or perforated cylindrical grains ( fig. 19). Powder is made in different
shapes to obtain certain types of burning (par. 17 c). The cylindrical
grains are made in various diameters and lengths. Grains vary in
diameter from 0.032 inch for caliber 30 cartridges to 0.947 inch for
16-inch propelling charges, and vary in corresponding lengths from
0.085 inch to 2.170 inches (fig. 20). For small-size grains either no
perforation or a single perforation is required. However, for larger
grains, seven equally spaced perforations are present in order to have
a large burning surface area (par. 17 e). The critical dimension is
the web size, that is, the average thickness of the powder between the
perforations. In color, the grains vary from a light amber to a deep
brown or black."
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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caterpillar
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Digging in the Net, I found one interesting text (sorry, I cannot say now, where in particular- it seems to me that here, http://parazite.nn.fi/roguesci/index.php/f-7.html but I'm not sure). After this forewords, read this:
"
Back in the '90s, I worked for a refractory metals and high performance ceramics outfit down in LA. We got a subcontract from Saco Defense for a
program to develop a cannon barrel that was resistant to the erosive effects of Nitramine-based propellants. One powder formulation in particular was
especially destructive to bore liners (even stellite!), shooting-out the bores in about 75 rounds. This is not acceptable performance in an automatic
weapon.
Most of these propellants contained more than 50% RDX. The mechanism contributing to the bore erosion had to do not so much with heat per se', but wth
hot nitramine particles coming in contact with the interior surface. While the isochoric flame temperature was somewhere around 3,000 Kelvins, the
surface temperature of the still- burning nitramine particles was somewhere above 4,000. These things were bouncing around inside the barrel like
pinballs, at supersonic speeds, and wherever they impacted the bore surface it would scorch a little pit. so it didn't take long to wear down the
forcing cone and rifling to the point where the barrel was unusable, spraying all over the range.
What we came up with, initially, was a subscale barrel in .50 BMG which, using the same propellant, lasted through a 10,000 round burst with no
detectable wear. The guys at Saco and ARDEC thought we were God. They had tried every trick in the book, 718 alloy, hard chrome, Stellite, and nothing
seemed to work.
What we came up with was a liner of pure Rhenium, CVDd on a sacrificial monolithic graphite mandel, with a 4340 chrome moly sleeve shrunk onto it. The
graphite was then burned out with an Oxyacetylene torch, modified to extend down the bore. Soon, a few were made in 25 mm for the Bushmaster cannons
on the Bradleys.
The "big barrels" cost $10,000 apiece, but were still a bargain when compared to the conventional barrels that cost two grand and wore out in less
than 100 rounds. Why they never went into full production is hard to figure.
Anyway, you can expect similar problems if you try to make rocket nozzles out of conventional materials. Carbon-Carbon may hold up for a "one shot
deal," but if you are shooting for a reloadable motor with a reusable nozzle, solid Rhenium is damned expensive. And if you're thinking about a
Rhenium coating on a CC or graphite nozzle, forget it. We tried that shit (against my better judgement) with a hypergolic satellite positioning
thruster, and it failed catastrophically at about 20 seconds of burn time, due to CTE mismatch.
For a gun propellant, though, the nitramine content provided about a 40% increase in muzzle velocity, which translated into about a 25% increase in KE
downrange.
Good luck, intrepid scientist!"
Women are more perilous sometimes, than any hi explosive.
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Hennig Brand
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Interesting post you found there. I found the following in, "Chemistry of High-Energy Materials" by Klapötke which is along the same lines as your
post about triple base propellants with RDX. It seems that the person who made that post, at the old E&W forum, may have known a few things this
author did not about the situation with nitramine propellants and barrel wear.
"To prevent erosion and the muzzle flash, a triple-base powder (NC + NG + NQ) with an NQ content of up to 50% is used, particularly in large calibre
tank and NAVY weapons. However, the performance of triple-base powders is lower than that of double-base powders (Tab. 2.4). In a triple-base powder,
particularly in large tank and NAVY cannons, NQ is replaced by RDX in order to increase the performance. However, the barrels suffer increased erosion
problems again due to the significantly higher combustion temperatures."
Homemade Cord Propellant
I just recently ordered one of these:
http://www.ebay.com/itm/2014-Kitchen-Stainless-Steel-Pasta-N...
It is a cheapie, but it may do at least for experimental purposes. It comes with three spaghetti noodle dies; 1mm, 2mm and 3mm and the drum is 6cm in
diameter. Hopefully I will be making cylindrical grains of propellant soon.
 
[Edited on 9-2-2015 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Hennig Brand
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DNT is used in fairly large quantities in some propellants (10% or more), that and the functions it performs made me think that maybe it is sometimes
mixed in the bulk formulation with the NG and NC at the time of manufacture (before propellant grain formation). This was maybe an incorrect
assumption, since apparently DNT applied to the surface of the grain travels by diffusion quite readily into the propellant grain creating a
concentration gradient which helps regulate the burn rate. One of the big obstacles has been, or is still, to control this diffusion process. DNT is
very miscible with NG and readily forms bonds with NC. It is possible that the DNT is only added after the propellant grains have been formed. So far
I am not sure.
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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