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sunnymoon
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[*] posted on 9-2-2006 at 14:03
compare


hello
In Akhavan’s book some information is given about detonation velocities of explosives and power of explosives . But I did not understand exactly. For example according to this book even tough nitroglycerin and picric acide have same density valeu that is 1.60gr/cm3, detonation velocity of picric acide is bigger than detonation velocity of nitroglycerin. And this point I can not understand why picric acide have bigger detonation velocity.
I know that in genaral if an explosive has bigger denstiy its detonation velocity is bigger. But if some explosives such as nitroglycerin and picric acide , have same density how can we compare their velocities? What can we say about them? What determined or effected velocities of these explosives?
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[*] posted on 10-2-2006 at 06:34


Nitroglycerine will have greater Vdet if it is fired with powerful booster, high diameter and strongly enclosed in metal container.

In fact not only density but also lots of facts are crucial for Vod. Like energy of detonation, enclosement...!!!

Nitro ester of methanol (myrol):
Its specific gravity is only 1.21 !
in a glass tube dia 3/12mm 2480m/sec
in a glass tube dia 3/7mm 2190m/sec
in a steel tube dia 3/15mm 2085m/sec
in a tube 30-40mm dia 8000m/sec !!!!!
in smaller tube 1500m/sec has been found,while in a wide tube detonation is propagated at a rate exceeding 6000m/sec

TNT with d=1,7 (higher than myrol) has Vod 7000 m/s (lower than myrol in its best)

Urea nitrate has maximum detonation velocity of 5km/s.
If you press it hard enough it becomes dead pressed and will not fire. Due to low energy of detonation!
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[*] posted on 10-2-2006 at 09:09


Those 8 km/s for MeONO2 are cited again and again, but mostly as "is said to reach...". There seems to be only one source (Naoum?) from early 20th century. Books from that time (especially Escales) also give 8,2 km/s for picric, and 7,8 for TNT, which are both too high. Back then, it was either Dautriche or some rotating mechanical device, both not that accurate.

BTW to get TNT to density 1.7 you will need a lab inside a black hole. Its TMD is something like 1.657 or 1.675 or so.

"Due to low energy of detonation!" This probably plays a role, but the main reason is missing voids / inner surface. Cast TNT, if slowly cooled (i.e. not creamed) will also not det from even a 50g Tetryl booster, unless in a many-inch diameter, thick-walled air drop bomb. That's why they press powder into hand grenades, or rather use comp B today.

On a side note, that chick's book, while not bad, is slightly too compressed. Plus it has been badly proof-read, e.g. "Small glass spheres containing oxygen can be added to emulsions to increase sensitivity". Nitrogen works as well, even vacuum bubbles do! Or "deflagration is not effected by the strength of the container'. She obviously believes in BP salutes made of paper bags... Or "the (critical diameter) phenomenon exists for homogeneous military explosives only. For heterogeneous commercial explosives the velocity increases with diameter." So ANFO has no critical diameter, and TNT won't benefit from big columns, or what? The book is still OK though, I am just picky lately.

For a better understanding I suggest Cooper, Paul W: "Explosives Engineering" or Melvin A. Cook: "The Science of High Explosives". There's formula for TMD and VoD depending on composition... :)
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[*] posted on 10-2-2006 at 11:34


Right about TNT density (1,65).
Also right, it is not that simple. For example for molten TNT, no matter what container and booster is used the Vdet should be constant. For PBX-es too.

In this dead pressed form the urea nitrate forms small chrystals stick to each other. It is heterogenous (different chrystal size and shape). Between chrystals there is plenty of air to support detonation. In theory it should be very senstitive...
But it is not...



[Edited on 10-2-2006 by simply RED]
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[*] posted on 10-2-2006 at 11:37


Methyl nitrate seems to have alot of conflicting data on the actual VoD. COPAE and Urbanski both list the same source, same edition and page, but different years (???) Then they list vastly different diameters for the same range of detonation velocities. And of course the journal is ancient so probably hard to actually find a copy :mad:
(M. Berthelot, Ann. Chim. et phys. 23, pg 485 (1891 or 1901 from Urbanski and COPAE respectively) if anyone wants to settle it)

However, Federoff has some really powerful explosive data (plate cutting test 240% of TNT) so I'm inclined to believe that it reaches 8000m/s. And it is mentioned again and again how exceptionally powerful it is.
But I think with the amount of conflicting numbers beyond "really power" and "extreme brisance" someone goofed early on and that threw off alot of people later on which now leads to confusion in the present days, some 80 years into the future.

It seems like on of those weird explosives with unexpectadely high power, like astrolite and tetranitromethane mixtures.
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