Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

youtube.com

Post reply on HN
Print view View original

31–40 of 306 posts

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#31

Post by Nextgrid »

Vladimof wrote: post #25
nine_k wrote: post #20

Earlier quoted context omitted.

Update: this is incorrect . The cone becomes very hot stream of molten copper. It melts through the steel plate, much like a jet of hot water melts through a block of ice. This happens fast enough that much heat does not have the time to escape from the impact site, despite high thermal conductivity of metals. The high pressure created by the explosion keeps the jet compressed from sides, too, so it does not fragment…

> much like a jet of hot water melts through a block of ice cold water can cut through steel also... https://www.youtube.com/watch?v=v0NVOThRooE

Waterjet cutting uses water to propel a powder which acts as an abrasive, like an infinite stream of sandpaper. I don't think water by itself will achieve much.

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#32

Post by KennyBlanken »

"I designed this, for, well, filling by the user. It means it can travel on airplanes and such"

Presenter: "DIY shaped charges, of course"

"Mmm yes"

I get that he likely meant it can be shipped on airplanes and local explosives used for easier logistics, but it's amusing to hear an explosive munitions expert brag about designing something so it can be carried on airplanes.

"This box, I'm pleased to tell you, is full of explosives."

Oh man, this guy is a hoot.

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#34

Post by WhitneyLand »

nine_k wrote: post #20
daenz wrote: post #16

I'm not sure I fully understood the explanation. So the copper cone is turned inside out and turns into a pointed wire that drives into the target? How is it that this wire can continue through the 1ft of steel? Is the force of the explosion flowing through this wire/tube, like liquid in a straw? And somehow it can sustain this through 1ft of steel?

Update: this is incorrect . The cone becomes very hot stream of molten copper. It melts through the steel plate, much like a jet of hot water melts through a block of ice. This happens fast enough that much heat does not have the time to escape from the impact site, despite high thermal conductivity of metals. The high pressure created by the explosion keeps the jet compressed from sides, too, so it does not fragment…

It’s not molten, and heat plays no role in the penetration ability. This is a very common misconception.

It’s simply focused kinetic energy that does it. The cone focuses the copper into a slug like object, and the slug becomes similar to an extremely powerful bullet.

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#35

Post by walnutclosefarm »

Vladimof wrote: post #25
nine_k wrote: post #20

Earlier quoted context omitted.

Update: this is incorrect . The cone becomes very hot stream of molten copper. It melts through the steel plate, much like a jet of hot water melts through a block of ice. This happens fast enough that much heat does not have the time to escape from the impact site, despite high thermal conductivity of metals. The high pressure created by the explosion keeps the jet compressed from sides, too, so it does not fragment…

> much like a jet of hot water melts through a block of ice cold water can cut through steel also... https://www.youtube.com/watch?v=v0NVOThRooE

Water is not doing the cutting there. Water is just the carrier for garnet abrasive, which does the actual cutting. Garnet is roughly three times harder than steel, so at high pressure cuts it very effectively.

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#36

Post by toomuchtodo »

Vladimof wrote: post #27
Animats wrote: post #2

That's a nice explanation of how anti-tank weapons work.

I wonder if that's how Ukraine killed so many tanks

My understanding is that it’s poor design, storing ammunition in a ring within the turret which turns out is a poor location from an integrity perspective. The “Jack in the box” vulnerability.

> The fault is related to the way many Russian tanks hold and load ammunition. In these tanks, including the T-72, the Soviet-designed vehicle that has seen wide use in Russia’s invasion of Ukraine, shells are all placed in a ring within the turret. When an enemy shot hits the right spot, the ring of ammunition can quickly “cook off” and ignite a chain reaction, blasting the turret off the tank’s hull in a lethal blow.

> For Russia, “the people are as expendable as the machine,” he said. “The Russians have known about this for 31 years — you have to say they’ve just chosen not to deal with it.”

https://www.washingtonpost.com/world/2022/04/30/russian-tank...

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#37

Post by Vladimof »

Nextgrid wrote: post #31
Vladimof wrote: post #25

Earlier quoted context omitted.

> much like a jet of hot water melts through a block of ice cold water can cut through steel also... https://www.youtube.com/watch?v=v0NVOThRooE

Waterjet cutting uses water to propel a powder which acts as an abrasive, like an infinite stream of sandpaper. I don't think water by itself will achieve much.

you learn something new everyday

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#38

Post by daenz »

daenz wrote: post #16

I'm not sure I fully understood the explanation. So the copper cone is turned inside out and turns into a pointed wire that drives into the target? How is it that this wire can continue through the 1ft of steel? Is the force of the explosion flowing through this wire/tube, like liquid in a straw? And somehow it can sustain this through 1ft of steel?

Sorry to answer my own post, but I watched it again and picked up on the key idea at 2:09.

The inverted apex of the cone drives into the steel, pushing the steel aside, but then the apex opens up and flows back along the outside of itself. In other words, any given part of this copper "wire" interacts with the steel only long enough to push it open, then it is replaced by new copper.

From this explanation, it sounds like the tunnel that has been "bore" through the steel would be completely coated from start to finish by the inverted copper cone.

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#39

Post by Vladimof »

giantg2 wrote: post #21
Vladimof wrote: post #15

Earlier quoted context omitted.

This type of explosive is very stable... nothing like nitroglycerin ...

The explosive is stable (small cubes of most plastic explosive can even be lit on fire and act as fuel). But there is still danger in correctly handling/connecting the detonator. I'm not sure, but I thing the acceleration charge might be a less stable type as well (obviously they aren't going to give us step by step instructions).

> (obviously they aren't going to give us step by step instructions).

nitrocellulose is very simple to make and detonate... and is also very stable.... I don't see why we need secrets... I played with that stuff when I was a teenager

Re: Shaped Charges – Sheet of copper going through 1ft of solid steel (2010) [video]

#40

Post by AdrianB1 »

Vladimof wrote: post #27
Animats wrote: post #2

That's a nice explanation of how anti-tank weapons work.

I wonder if that's how Ukraine killed so many tanks

No, it has nothing to do with shaped charges; they are using missiles that explode on top of the tanks. Most armor of the tank is frontal arc, some on the sides, top armor is minimal, just a few centimeters, so it can be easily penetrated by explosions of these missiles or by aircraft cannon fire from platforms like A-10.
Post reply on HN