Sciencemadness Discussion Board

Dense inert metal explosives

Fusionfire - 12-11-2012 at 06:13

Suppose you had an explosive placed a short distance away from:
1) A steel plate
2) A concrete slab
3) Sand

and detonated.

What difference would you expect to happen to the cratering ability of the explosive against the slab if:
1) The explosive was AN-based with a relatively low VoD
2) The explosive was HMX-based with a relatively high VoD
3) The explosive consisted of a 50:50 composite by volume, of HMX and tungsten powder

Would you get more significant cratering with (3) vs. (2) due to better momentum transfer to the target media?

Do you expect the cratering capability of (3) to be superior to (1) and (2)?

SM2 - 12-11-2012 at 08:01

the only dense (otherwise) inert metal explosive I can think of is U-238. it is very dense, and is only fissionable through fusion. in other words, depleted uranium is fissiable but only through an initial fission to fusion process, where of course the first light fission engine is U235. Even w/ lasers, lenses, shaped charges, and extreme compression, U238 won't go critical. you need sustained burning LiD fusing all around it. makes for a very dirty bomb. If anyone has a link to a cold war plan by soviets to park barges filled with LiD (humungaform H-Bomb), I'd be oh so grateful.

franklyn - 12-11-2012 at 09:14

@ Fusionfire

The effect from close proximity explosion is enhanced greatly by tamping.
Something which is never discussed here at all except by me. An explosive
composition containing dense inert matter reduces the energetic portion
otherwise available for the same volume , so it is a tradeoff. The effect
against a metal plate is augmented but only some. You're much better
off shaping the explosive for Munroe effect. Applying tamp and shaping
will enable a low VOD explosive to perform close to that of a high VOD
explosive that does not apply those methods.

http://www.sciencemadness.org/talk/viewthread.php?tid=5096
Small Scale Plate Dent Test for Confined Charges ( appallingly bad resolution )
www.dtic.mil/dtic/tr/fulltext/u2/496898.pdf

Low VOD means to be buried for use in moving earth ( cratering )
High VOD is good for shattering rock and against metal as I described.

.

caterpillar - 12-11-2012 at 20:50

Quote: Originally posted by Fennel Ass Ih Tone  
the only dense (otherwise) inert metal explosive I can think of is U-238. it is very dense, and is only fissionable through fusion. in other words, depleted uranium is fissiable but only through an initial fission to fusion process, where of course the first light fission engine is U235. Even w/ lasers, lenses, shaped charges, and extreme compression, U238 won't go critical. you need sustained burning LiD fusing all around it. makes for a very dirty bomb. If anyone has a link to a cold war plan by soviets to park barges filled with LiD (humungaform H-Bomb), I'd be oh so grateful.


It is off-topic, I guess. But if you have an interest in such thing, read http://scilib.narod.ru/nukes.html and http://scilib.narod.ru/Nukes/Ioffe/Ioffe.html .The second one particularly explains corresponding physic. Joseph The Terrible wanted to exclude US from his attempt to gulp the rest of Europe in early 50-s. Ships with giga-bombs (TNT equivalent some giga-tons), been placed near US coast line, would had been heavy argument to US do not interfere in possible war in Europe. But there was some problems, for example how to build such device. Soviet physics tried to find out, if such devise could be constructed using only D which is relatively cheap. H-bomb needed some T, which cannot be obtained without nuclear plants, but their ability to produce this vital component was restricted. Well, read these texts, if you know Russian enough well. (BTW, no fusion can get U238 to blow up. Only large amount of fast neutrons, which occurs when D+T reaction is going on).

AndersHoveland - 13-11-2012 at 01:18

In most situations, the mechanical energy released from an explosion will be greater than the kinetic energy of an accelerated dense metal within the same volume. With electromagnetic acceleration (railguns), there is potential for the kinetic energy to exceed the energy a chemical explosive can store in the projectile.

Many people have wondered about how the effects of an explosive filled projectile compare to a solid metal projectile.
At very high speeds, the kinetic load of a solid round can carry more energy than the ammount of explosives that could be packed inside it.

An object in "low earth orbit" moves at 27,400 km/h, and has an energy density of 33MJ/kg, while HMX has an energy density of 5.7MJ/kg.
Bullets from rifles have velocities up to 1200 meters per second (which is 4,320 km/hour). I will let you do the math.
Remember: mass multiplied by the square of velocity, then divided by two, equals kinetic energy. This means that a kg of something in low earth orbit has about 123 thousand times as much kinetic energy as a bullet from a rifle.
It can be calculated that an equivalent weight of HMX detonating will release 68 thousand times more energy than the kinetic energy from a rifle bullet.

However, it should also be remembered that only a fraction of the energy from an explosion is released as mechanical energy, and not all the kinetic energy released by an explosion is in the optimal direction to cause damage.

The kinetic energy from a projectile stays more focused as it penetrates into the armor than an explosive vortex. A metal projectile also has a much higher density than typical chemical explosives, depleted uranium is exactly ten times more dense than HMX for example.

In conclusion, my quick calculations suggest that filling a projectile with an explosive would be more effective than a plain solid projectile for handheld guns. For high-velocity armor-piercing projeciles, there are a few reasons why explosive filling probably is not as effective. This is a science-focused analysis, and I otherwise know nothing about guns and ammunition.

One additional reason that ammunition often explosive filled is to spread the damage over a wider target area. An extreme of this, of course, is an explosive squash head, where explosive putty gets spread out against the target upon impact for maximum surface area before being detonated.



[Edited on 14-11-2012 by AndersHoveland]

caterpillar - 13-11-2012 at 03:01

Quote: Originally posted by AndersHoveland  

Bullets from rifles have velocities up to 1200 meters per second (which is only 78km/h).


With all my respect, check your numbers. Moreover, at the low orbit at counter course relative velocity will be near 16 km/h. It explains the principle of so-called kinetic weapon. Cloud of shrapnel, moving against a satellite or a warhead, can destroy it. Modern electromagnetic guns uses shells without explosive at all.

WaveFront - 13-11-2012 at 10:51

Quote: Originally posted by AndersHoveland  


Bullets from rifles have velocities up to 1200 meters per second (which is only 78km/h). I will let you do the math.


?? 1200 m/s is 4320 Km/h; 78 Km/h is reached even for my car

AndersHoveland - 14-11-2012 at 00:13

My mistake, obviously 1200 meters per second is 4,320 km/h. mistake corrected