Hemispherical Lined Charges

[Axt]

<center><table cellpadding="20"><tr><td><table border="1"><tr><td colspan="2"><center><b><font size="2">Properties</b></center></td></tr><tr>
<td><font size="2">Explosive</td><td><font size="2">ETN/NM/NC</td></tr><tr><td><font size="2">Charge Weight</td><td><font size="2">35g</td></tr><tr><td><font size="2">Liner</td><td><font size="2">25mm Cu</td></tr><tr><td><font size="2">Liner Shape</td><td><font size="2">Hemisphere</td></tr><tr><td><font size="2">Casing</td><td><font size="2">PVC</td></tr><tr><td><font size="2">Standoff</td><td><font size="2">62mm</td></tr><tr><td><font size="2">Target</td><td><font size="2">16mm Plate</td></tr></table></td><td><center><img src="http://ww1.altlist.com/~52497/rogue.altlist.com/images/1inchscsmall.jpg"></center></td></tr></table></center>

Hemispherical liners are much easier to source or make then conical liners, and achieve much the same effect. A military 2" Cu hemispherical lined charge at a VOD of 7800m/s via RDX/TNT can penetrate up to 300mm of steel. While we cant totally duplicate the tolerances used in creating that, we can easily source the materials to improvise our own.

Liners can be sourced in many sizes for legitament reasons, heres (http://ww1.altlist.com/~52497/rogue.altlist.com/images/cuhemi.jpg) some copper liners ive managed to find, dont ask where, there not hard to find, hint - search for measuring spoons and ladles. Copper egg beating bowls are also common ... if you want a foot wide charge :D

The charge shown in this thread used the largest of the 3 liners on the left, a thin walled 1" copper liner. The explosive used was ETN/NM/NC plastic mixed to OB. On detonation the charge performed well, with the jet completely penetrating the target (http://ww1.altlist.com/~52497/rogue.altlist.com/images/plate.jpg) and created a large crater in the wet ground. Some fragments of liner were sprayed out to one side (bottom left of hole in bottom left picture), perhaps as the result of the detonator being slightly off centre.

<center><img src="http://ww1.altlist.com/~52497/rogue.altlist.com/images/shapedcharge.jpg">

MOVIE ADDED (http://geocities.com/roguemovie3/)</center>

Yes, in hind sight I know I should have placed the plate on top of the roo and fired it to see what sc jets do to body tissue, its not something I thought of at the time. I couldnt even find any penetration wounds from the PVC, actually I couldnt find any remnants of the charge at all. PVC is very brittle under impact which forms very small fragments that dont travel far, if I was to skin it I guess there would be many very small holes.

Anyone know the advantages/disadvantages of hemispherical over conical liners?

[IDTB]

Arg! The archive the movie is in seems to be currupted. It also seems after downloading that I used up your maximum bandwidth..

Perhaps you could just upload it to the FTP?

[0EZ0]

Very nice presentation Axt. I'm always impressed with the quality and depth of your reports.

When using high VoD composites, plastics do tend to shatter and fragment into many small pieces. Under some circumstances the plastic can even atomize into quite small particles and weld to nearby surfaces. It's interesting to catch some of the frags to see what they look like.

Well the conical cone you have used seems to have performed quite well. It may well be that there was a bubble or similar inconsistency in the charge close to the inside surface of the liner causing the spray. Under the intense conditions, as the copper liner liquefies, it would be conceivable that a bubble caused a lag in the formation of the penetrating slug, making that portion of the liner not fully fold around, and spray a little bit outward. The overall effect would differ little though. Thats my theory. Still a nice punch through the plate.

Keep up the good work :)

[Axt]

The movie may be running out of bandwidth when only partly downloaded .. maybe. Which with geocities seems to be getting less and less, wankers dont even tell you how much you can use. Ill try find somewhere else, though it shows nothing the still frames dont, very smokey.

The reinstatement of picture imbedding and HTML was my que to start making things look a bit nicer, and hopefully prove that more freedom over post formats can be a good thing.

The detonator was actually a bit off centre, I had it glued into the endcap which moved as it was setting, maybe 2mm off. I remember seeing photographs of a sc-jet, from a charge that had been drilled into to simulate bullet/shrapnel damage, created a funny curved jet that seemed to defy physics.

[mongo blongo]

Very nice Axt! I do enjoy reading your reports. :)
If you have ETN then it would be very interesting to cast it into the shaped charge and see if there are any significant changes in penetration. Cast ETN with suspended RDX crystals would probably be one of the best compositions you could use for this.

[Axt]

The movie should work now.

I intend to let someone else melt cast ETN first ;), anyway heres an x-ray picture of a sc jet with a hole (or bubble) in it. You can see how it sprayed out in a loop in the direction of the defect, so yes a small defect could have caused the bit of spray.

<center><img src="http://ww1.altlist.com/~52497/rogue.altlist.com/images/scho.jpg"></center>

[Flake2m]

That video was quite good. What was with the dead Kangaroo though?

Hemispheres would be easier to make, all though they would not be perfectly round. SWIM could make one by obtaining a copper sheet and either;
1. Using a press to stamp it into the shape of a hemisphere
2. Placing the sheet over a an object such as a bowl and then banging it into shape, using the shape of the bowl as a template.
The second method can use basic eqipment - A hammer, A ball or bowl etc and some sheet metal, though the shape will be a bit lumpy.

Would the thickness of the copper have anything to do with the penertration of the jet?

[Axt]

To see the effect of PVC shrapnel, beats giving it to the dogs. Though in the end it meant nothing as I wasnt keen to skin the bastard.

The best process for making copper hemispheres is done by adapting a lathe and using what is known as "metal spinning", heres a good page on this process - http://www.coe.ufrj.br/~acmq/spinning/

Thats how the one I used was made.

[Flake2m]

Axt; The method I had explained, was for people that didn't have access to metal work equipment, such as a metal lathe.
While those Metal hemispheres that are shown on that link are rather nicely crafted, not everyone that wants to experiment with hemispherical shaped charges has the skill level to make them.
Also buying metal hemispheres can be an expensive process, the ones on that link aren't likely to be cheap, plus SWIM would need quite a few of them to conduct enough tests.