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

121–130 of 306 posts

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

#121

Post by chemeril »

Brian_K_White wrote: post #50
WhitneyLand wrote: post #34

Earlier quoted context omitted.

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.

So it's like that old picture of the grass straw driven through the telephone pole by nothing but hurricane wind? The flimsy straw could do it simply because of how fast it was moving. The strength of the straw doesn't matter, simply it's mass, moving that fast, carries itself through, ie the leading edge is not being pushed from behind like a nail, more like a bullet with a string attached? Setting aside the simplif…

Yes, that's reasonable. By the time the jet hits the target the explosive provides no motive force whatsoever: it's purely a momentum game.

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

#122

Post by chemeril »

GartzenDeHaes wrote: post #113
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…

A plasma technically. And it doesn't exactly penetrate, it pushes the steel atoms aside very literally like sticking your finger in butter. Edit: obviously it penetrates, but not in the way that you would expect.

Certainly not a plasma. It's a coherent spear of hydrodynamic copper, not a bunch of charged ions floating around.

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

#123

Post by appletrotter »

londons_explore wrote: post #95
blip54321 wrote: post #66

Earlier quoted context omitted.

I think the line is when your troops shoot their troops. Providing weapons has been a US-Soviet past time for the whole Cold War. In this case, I think the US could have even moved in troops without being at war, early in the invasion. It just needs a pretext. By far the best response a week in, when Russia claimed chemical weapons, Nazis, etc., would have been to send in a multilateral force to investigate Russia's…

If you look on various dating apps big in Ukraine right now, you'll see there are a lot of Americans new to Ukraine right now. I've got a feeling we might be pulling a Russia... Ie. None of our troops are there officially, bit there's an awful lot of troops volunteering and 'on holiday' and 'advising' there.

Foreign legions are also a standard thing with this.

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

#124

Post by chemeril »

giantg2 wrote: post #42
Vladimof wrote: post #39

Earlier quoted context omitted.

> (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

Is that what they are using for the acceleration charge (not the main charge!)?

It is not. Nitroglycerin doesn't have the capacity to detonate (necessary for triggering the main charge). Detonators (the acceleration charge you mention) are usually an explosive train starting with a sensitive primary like lead azide moving up to a secondary or pseudosecondary output charge like PETN.

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

#125

Post by swimfar »

nradov wrote: post #82
toomuchtodo wrote: post #36

Earlier quoted context omitted.

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 r…

This Chinese TV news video shows a wild example of the Jack-in-the-box vulnerability. A Russian tank in Ukraine gets hit and the turret takes off like it's headed for orbit. https://youtu.be/ZsiHlmJ9myg

The actual footage starts at 2:26

https://youtu.be/ZsiHlmJ9myg?t=146

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

#126

Post by aurizon »

Vladimof wrote: post #39
giantg2 wrote: post #21

Earlier quoted context omitted.

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

When I was in college in Toronto in 1961 there was a surplus store. All manner of WW2 radios etc. I looked at one pile and it was about 15 rolls of primacord. This was a long 5/16 hollow tube of vinyl filled with pure TNT. It resembled rope = rope pile/ $3/roll of 100 feet. 2/$5. I knew what it was, so bought it all. it being worth $25-30/roll/ I was an Engineering stoont and Russia had just set of their Czar bomba. We engineers had a group called the BFC(Brute Force Committee), so we had to have a bomb for Skule Nite. In the quad we set off about a quarter pound of this prima cord with a lighted fuse detonator. We paced off a 100 meter circle for crowd control and Mr Riggs set it off. Prima cord has a hugely fast rate of propagation of the detonation wave, so we heard an intense CRACK, not a boom with a few tens of milliseconds, but a true faster than sound detonation wave. No harm was done as had just set of the Skule cannon which alerted people to cover their ears. I explored these rolls with playing with the Monroe effect, A nice shapely rabbit hole. https://en.wikipedia.org/wiki/Shaped_charge

I stamped initials in steel beams etc. Hardest thing was getting detonators = well controlled. Never tried to make a tank buster.

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

#128

Post by gonzo »

nullc wrote: post #94
Nextgrid wrote: post #31

Earlier quoted context omitted.

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.

Waterjeting without abrasive is a thing, it's used for soft materials like rubber... and there are some companies marking higher pressure approaches for metal (though usually with tiny amounts of abrasive rather than none at all).

It’s also used in commercial food prep.

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

#129

Post by infofarmer »

nostrademons wrote: post #107

The Wikipedia article on shaped charges is fascinating: https://en.wikipedia.org/wiki/Shaped_charge The penetration distance is proportional to the diameter of the charge (counterintuitive; you'd expect the height), and can be up to 7x as large. So a ~5 inch charge shown in the film can penetrate up to about 3 feet of solid steel. Also, all of our known defenses against shaped charged rely on the assumption that the…

There are many more types of active defenses other than reactive armor:

https://en.wikipedia.org/wiki/Active_protection_system

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

#130

Post by sophacles »

bawolff wrote: post #105
dvtrn wrote: post #41

Earlier quoted context omitted.

"What makes me a good Demoman? Well if I were a bad Demoman, I wouldn't be sitting here discussing it with you, now would I?" One of the silliest, hilarious but on point thing I've ever heard uttered from a video game character

Survivorship bias personified

But... in a field where being bad at your job is fatal, is it really a fallacy?

Serious question - just like quoting an expert in the relevant topic isn't an appeal to authority, etc.

Post reply on HN