darel - 2-8-2008 at 08:16
I was thinking instead of binding nitro to a inhert material I could use RDX crystals instead? Not surewhat to expect. Anyone have any ideas?
Stability, gel/liquid, detonation rate?
Leander - 2-8-2008 at 13:18
I dont have any experience wih RDX/NG but I have with PETN/NG. I used a 7/3 ratio by mass, wich gives a dough-like material with a density of roughly
1.6g/cc. Ratio's using more NG, or coarse crystals gives seperation, resulting in a dirty not so usefull slurry.
With RDX the denstity with be pretty much the same, or cource depending on the crystal size and shape. NG, as any liquid, fills of the small gaps
between the crystals normally filled with plain air, allowing the shockwave to travel much more undisturbed and uniform. Even though, some air will
allways remain trapped. Using a good inert plasticiser like PIB gives you higher densities and eventually (depending on charge shape and size) yields
a more brisant mixture.
The NG sensitises the composition quite a lot, and in fact, the RDX sensitives the NG to, because of the crystals, preventing a low order detonation,
witch occurs quite easily with NG in small diameters. Therefore, PETN/NG as well as RDX/NG are exelent booster-charges, wich will outpreform plane
PETN, RDX and even PBX in amounts under 1 gram and in small diameters. The critical diameter will probably be somewhere arround 2-3 for PETN/NG and it
can be initiated by as little as 0.05 grams of Ag2C2*Ag(NO3)2 of AgN3. I expect RDX/NG to have a CD of ~5mm, sufficing a minimum initiation ammount of
roughtly 0.01 grams of the previous mentioned primaries. As you can see, its not hard to guess that the mixture is also pretty sensitive to
stimulation by friction and shock. To be on the save side, treat it as if it would be just plain NG. The acceleration rate of the mixture will be a
little lower though. The Max. VoD will probally be ~ 8000 m/s.
Edit: Spell check 
[Edited on 2-8-2008 by Leander]
Boomer - 7-8-2008 at 07:32
RDX and PETN mixed with NG behave totally different. PETN is soluble, giving a dough-like material, while RDX is simply wetted by the NG.
The wet crystals will have a critical diameter far below 5mm, with fine crystals at least. In contrast the putty with PETN can become inert just like
old blasting gelatine does, I even had low-order detonations with NG/MHN, which is considerably more sensitive for some time after preparation. This
was after 2+ years of storage though.
The mix of NG with a solid nitrate ester (ETN/PETN/MHN) can serve as a binder/plasticiser for RDX (or another crystalline HE that is insoluble), if
the ratio is altered to get a sticky goo instead of a dough. Even if it is not as good a binder as PIB/sebacate, and you will need more than 9% even
with bimodal RDX crystals, it outperforms C-4 in energy, while being at least equally brisant. Semtex is absolutely no match with it's 30% inerts.
Nothing beats a binder that itself shoots at 8 km/s!
BTW the critical diameter / wedge thickness of superfine PETN, even with *inert* binder, is far below what you estimated for the mixture with NG. I
remember some figure like 0.4mm for XTX8003 (PETN based PBX, silicone rubber bound IIRC).
And while NG is usually not good at propagating its own detonation in small amounts, and prone to low-order dets, I had it propagate for 45mm through
a 0.5mm ID hypodermic needle, from the heated tip right back into the barrel of the syringe. That was 25 years ago, and the only reason my hand was
not gone was that I only sucked up 2-3 drops for each test.
It was still unexpected, it normally just puffed out the hot tip making a sputtering sound when i pressed the plunger slowly, with the needle tip in a
flame. The resulting bang told me I had been dead wrong: Because it did not detonate when a drop hit the floor like in the movies, and did not even
explode when touched by a flame, I had wrongly assumed it was no 'real' nitro.
Leander - 9-8-2008 at 10:55
The reason I overestimate the critical diameter of RDX/NG, is because in my experience, RDX quickly becomes quite insensitive to initiation at
relatively high densities.
I once made pure RDX based detonators, fired with with 0.05 grams of DS on top. Because of the low density and good crystal shape they did just fine.
On the other hand I once tried to initiate 30 grams of 85/15 RDX/Binder with atomised RDX, that failed to detonate when fired with a detonator filled
with over 0.7 grams of rock hard pressed PETN. Such a cap on its own can smash holes through 3mm steel plate, and can probably rip off your entire
hand when accedentally fired.
[Edited on 9-8-2008 by Leander]
vulture - 9-8-2008 at 12:39
This falls within practical design of explosive devices and thus outside the scope of this forum.
Thread Closed.