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

131–140 of 306 posts

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

#131

Post by htk »

matheusmoreira wrote: post #106
mhh__ wrote: post #91

Earlier quoted context omitted.

The younger guy in this clip actually ended up retiring because he got brain damage in a contraption he designed for this show. https://www.bbc.com/news/uk-58762935

> The injuries happened when Mr Stansfield, who was 42 at the time, filmed a Bang Goes The Theory feature about the relative safety of forward and rear-facing child car seats. > The episode saw him "strapped into a rig like a go-cart which was propelled along a track into a post". I'm sorry but to me this reads like something out of Darwin Awards.

That’s why he was awarded around half of what he demanded, because BBC shared the responsibility by accepting the stunt, but he was also responsible for doing it.

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

#132

Post by tshubbard »

Shaped charges are also used to create the holes (perfs) in wellbores prior to fracking. The shaped charges blast through 1/2 inch of steel pipe and then a foot or two of rock. Sand and water are then pumped through the holes to prop open the rock and allow oil, gas, and water to flow out with less resistance.

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

#133

Post by foucalt-apathy »

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…

Are you certain that a hurricane can blow a straw through a telephone pole? I hadn't heard of this phenomenon and was interested. I was unable to find a good source.

According to this article, the National Oceanic and Atmospheric Association thinks it's not possible:

https://www.livescience.com/39270-tornado-straw-into-tree-wo...

(Alternative explanation in the article: the tree twists during the hurricane, cracks temporarily open, and debris gets stuck in the cracks.)

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

#134

Post by bawolff »

sophacles wrote: post #130
bawolff wrote: post #105

Earlier quoted context omitted.

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.

Its still a fallacy because some people are just lucky instead of being skilled, and its entirely possible to confuse the two.

In the same way, an appeal to an authority is better than nothing, but its still a really weak argument. You can misunderstand authorities and authority can be mistaken or suborned. Its a reasonable argument if nobody knows much about the topic, but its never convincing if people are learned in the topic; the benefit of an expert is not that they are experts, its that they know how to defend their position with reasoning. As the motto of the royal society says "Nullius in verba".

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

#135

Post by askvictor »

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?

I'm impressed (and a little confused) at the idea the explosive is essentially sitting untethered on the target. I would have thought the entire contraption would shoot up with the explosive force being reflected off the ground, but I suppose there's enough energy in the initial blast (before the reflection) to form the copper 'bullet'. =

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

#136

Post by hunter-gatherer »

In the US/Iraq war such contraptions were commonly referred to as EFPs (explosively formed penetrators). My platoon was once hit by a four-array EFP that was hung behind a cement wall (US forces would often line streets with barricades like this) so we couldn't see it. It went through the concrete wall, the humvee, and took some legs with it. Brutal things they were. We avoided prolonged truck excursions, but I remember we used to always sit with our arms and legs as staggered as possible--The thought being that if an EFP went through, you might get lucky and only lose one arm/leg instead of two. Of course it probably didn't help... but whatever.

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

#137

Post by function_seven »

ethbr0 wrote: post #103
IncRnd wrote: post #99

Earlier quoted context omitted.

There are old people who use explosives. There are bold people who use explosives. But, there are no old, bold people who use explosives.

Reading Ignition! convinced me that there's more than raw intelligence to experimenting with energetic chemistry. https://www.amazon.com/gp/aw/d/0813595835/

Note to anyone that might be tempted to get this as an audiobook: Don't!

It didn't occur to me that the subject matter would be incompatible with narration, but it (IMO) just doesn't work that way. Large portions of the book have equations and heavy notation. Here's an actual passage:

> it can be simplified to cee equals bracket two aitch over em end-bracket to the one half power times bracket one minus parentheses pee e over pee cee end parentheses to the ar over cee pee power end bracket to the one half power.

Yeah, I just couldn't keep listening to that. I need to get a print copy, because the subject matter is interesting.

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

#138

Post by zhengyi13 »

bawolff wrote: post #134
sophacles wrote: post #130

Earlier quoted context omitted.

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.

Its still a fallacy because some people are just lucky instead of being skilled, and its entirely possible to confuse the two. In the same way, an appeal to an authority is better than nothing, but its still a really weak argument. You can misunderstand authorities and authority can be mistaken or suborned. Its a reasonable argument if nobody knows much about the topic, but its never convincing if people are learned…

Luck eventually runs out. That's not to say you're wrong, only that I expect the distribution of the lucky amongst the skilled tends towards zero over sufficient time.

"Beware old men in a young man's game."

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

#139

Post by tootie »

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…

Great video on the engineering of the Javelin and why it's so simple and effective: https://youtu.be/SUdHzKRiBX8

The Javelin has multiple tricks up its sleeve to defeat sophisticated armor and Russian armor is just behind the curve. It's a literal arms race to add more layers of defense and more layers of attack and right now, NATO is far ahead.

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

#140

Post by Terry_Roll »

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…

Alot of things were developed during WW2 like an Earthquake bomb https://en.wikipedia.org/wiki/Earthquake_bomb and in the 50's the first of these were developed, a Tsunami bomb https://www.telegraph.co.uk/news/worldnews/australiaandthepa...

A scaled down model of the Möhne dam where the bouncing bomb was used can be found at the BRE site in Watford on your way to the lunch canteen. https://bregroup.com/ipark/parks/england/visit/ https://en.wikipedia.org/wiki/Bouncing_bomb#Re-creating_the_...

Post reply on HN