How hard would i have to throw a rock to penetrate the frontal armour of a tank?

[Ethris]

I'm really glad this thread remains unclosed, while ones which had active and productive discussions have been silenced.

Thanks mods, shilling for your masters as usual. Really making this place great!

[Deleted]

pretty hard i reckon

[Halyon]

I'm really glad this thread remains unclosed, while ones which had active and productive discussions have been silenced.

Thanks mods, shilling for your masters as usual. Really making this place great!

Omg, general OT is having activity?! HERESY!

OT; I suppose if your rock was made of unobtanium and was shot out of a canon, you could get through some frontal plates...so...no chance whatsoever with throwing speed.

[Stormspark]

Then there's no way in hell anything the size of a small projectile that'll go through the frontal armor of a tank.

It's a dumb place to aim.

Well, speaking from a strictly theoretical perspective, it COULD...but you're going to need help from relativity to do it. Which means the projectile going a signifcant fraction of c. Which generates many other problems (see the relativistic baseball article). That's not even going into HOW you would get the projectile up to that speed to begin with.

http://tvtropes.org/pmwiki/pmwiki.ph...sAreJustBetter

[zEmini]

Might be easier to build your own water jet instead.

[dextersmith]

Can you lift 90 kilos to throw it or do you mean to launch it?

[jackofwind]

I'm really glad this thread remains unclosed, while ones which had active and productive discussions have been silenced.

Thanks mods, shilling for your masters as usual. Really making this place great!

How dare the mods leave a completely harmless physics-related thread open while they close political debate threads full of soapbox warriors!

It's almost as if these forums have a set of rules that moderation is based on!

[TStreets]

2,500 feet per second

[WintersLegion]

Depends. What shape is the rock? How much of a spin can you give it? Are you going to heat the rock up before throwing it, and to what temperature?

Also how big is the rock and what is the rock made out of.

[Adam Jensen]

Also how big is the rock and what is the rock made out of.

Is the rock made out of old Nokia phones? If so, the tank, even if it's an M1 Abrams, is screwed.

[Whitedragon]

I have always wondered about this, it'd be really useful in case the Russians invade again.

Oh yeah, the rock weights 90 kilograms.

Well if we are talking any ordinary rock, then to tell the truth it probably wouldn't matter how hard you shoot that rock out. Its just going to disintegrate upon contact with the much more dense and refined mettle plating of the tank. In theory though if you could get it going fast enough, you could destroy the tank with sheer kinetic force (think like smashing something with a hammer rather then piercing it like a blade.).

Is the rock made out of old Nokia phones? If so, the tank, even if it's an M1 Abrams, is screwed.

Even harder, its made with the most resistant material known to man.... "Nintendonium"

[Stormspark]

Well if we are talking any ordinary rock, then to tell the truth it probably wouldn't matter how hard you shoot that rock out. Its just going to disintegrate upon contact with the much more dense and refined mettle plating of the tank. In theory though if you could get it going fast enough, you could destroy the tank with sheer kinetic force (think like smashing something with a hammer rather then piercing it like a blade.).



Even harder, its made with the most resistant material known to man.... "Nintendonium"

Any material can penetrate any other material if it's going fast enough. Obviously "fast enough" in this case is not going to happen without something silly like the rock moving at 10% of c, which there's no way to actually do in practice. Relativity can do some WEIRD things.

https://what-if.xkcd.com/20/

[WintersLegion]

Any material can penetrate any other material if it's going fast enough. Obviously "fast enough" in this case is not going to happen without something silly like the rock moving at 10% of c, which there's no way to actually do in practice. Relativity can do some WEIRD things.

That isn't really true plenty of things that if they reach a high enough speed to actually penetrate would be destroyed by the very speed they are traveling at

[Breccia]

The Tiger Nazi tank is probably a good place to at least start.

The front of the tank was covered in RHA, basically extra-strong steel, with a UTS of about 150,000 pounds per square inch. Let's say you threw a 3-inch round rock at the front of the tank and wanted the rock to punch through. In order to do that, it would have to make a hole with a circumference of about 19 inches. As the front of the Tiger's impressive armor was about 4 inches thick, you'd need to break through 76 square inches, taking 11.4 million pounds of force. We'll come back to that.

Next comes the force by impact. The rock, if stopped, will decelerate over a distance of no more than 5.5 inches (the thickness of the armor plus its radius, any more, and it got through). And assuming granite, it has about 14.5 cubic inches and weighs about 22 ounces.

The calculations aren't all that bad, but I like to refer people to this sweet car crash site:

http://hyperphysics.phy-astr.gsu.edu/hbase/carcr.html

Wander around with the settings a touch and you'll find the stone has to be going a whopping 10,000 MPH at least. EDIT: So, you're approaching escape velocity at this point. The rock would probably burst into flames and/or be torn into pieces smaller than sand.

That sounds extreme, doesn't it? There's a reason why tank shells and bullets are made of metal, typically dense metal, not rock. Depleted uranium shells are popular for a reason (and toxic for another reason). Tank shells are also a hell of a lot larger. And we haven't even gotten into the genius design of the Tiger's front angle, which would deflect most American and British tank shells fired at its front.

Maybe a baseball-sized rock isn't your thing. The good news is, the larger the rock, the better this works out. The volume increases by an exponent of three, but the armor it has to tear through only by a factor of two. Eventually, the rock will work -- just like tin foil will deflect grains of sand, but not the granite "baseball". However, if you're capable of throwing a rock with 11.4 million pounds of force, you could just walk op to the 50-tron tank and flip it over.

[Danuru]

Any material can penetrate any other material if it's going fast enough. Obviously "fast enough" in this case is not going to happen without something silly like the rock moving at 10% of c, which there's no way to actually do in practice. Relativity can do some WEIRD things.

https://what-if.xkcd.com/20/

Read that to the end, that was pretty great. Loved the ending

That isn't really true plenty of things that if they reach a high enough speed to actually penetrate would be destroyed by the very speed they are traveling at

I'm not so sure after reading that link. From what I understand, once you get to "almost" the speed of light, disintegration doesn't really do anything, because no matter what form it is in, it's still matter travelling at insanely high speeds.

[Jun]

Would depend on multiple factors, including rock density, hardness on the Mohs scale, point of impact, type of tank, velocity of said tank in relation to velocity of rock, ballistic trajectory/motion, and a few other minor factors.

Short version: You'd have an easier time getting an RPG and firing it than getting that rock through a tank's frontal armor.

[Kellhound]

The way I understand about those things, is that the hull is measured in what it's equivalent in steel. Tanks fronts have something like 1200-1500mm worth of steel in protection. So you wouldn't need to know the exact make up or thickness, if you know what it equals to in steel. So if you have something that penetrates 1500mm of steel, then it will penetrate whatever makes up to 1200mm equivalent in steel for example.

Its measured against rolled homogeneous armour equivalent (RHAe). Most armored vehicles use a base hull made of RHA (in the US it is a nickel-chromium-molybdenum steel alloy) with composite armor and perhaps reactive armor layers. Note that RHAe varies depending on the type of penetrator being compared against (HEAT, HESH, APFSDS, etc) and can very greatly (A T-90 with Kontakt-5 ERA has a maximum of ~830mm RHAe against APFSDS but ~1350mm against HEAT).

[Masark]

hm why not do this instead:

-get a rock.
-Get a sheet of tank steel

Tank armour hasn't been simple steel since shortly after WW2 when shaped charge anti-tank rockets rendered it obsolete. Everything nowadays is composite and/or reactive armour.

About the same punch as a 50 cal. sniper rifle. https://en.wikipedia.org/wiki/Barrett_M82

Not even close. Cartridges even larger than the .50 BMG (like the Russian 14.5×114mm (.50 BMG is 12.7×99mm)) couldn't deal with tank armour in WW2 and modern armours are much tougher than that.

[Breccia]

Would depend on multiple factors, including rock density

Probably not. Almost all standard rocks hang out at 2.7-3.0 specific gravity. Heavier rocks are...well, basically metal/rock hybrids.

hardness on the Mohs scale

There isn't a "rock" alive that beats the hardness of steel. At least, as far as this issue goes. Even quartz is less hard than RHA. Now, if you're talking solid gemstones, maybe. But I counter that, at the speed that's necessary, the hardness isn't the real feature in question. 90kg of Starbucks Double-Shot flying at Mach 12 is going to have substantial impact whether it's in cans or not.

point of impact, type of tank

Valid and valid. Every tank has a weak spot. Of course, you're then asking about accuracy in addition to throwing speed. Since we're clearly in superhuman territory I see no reason this can't be part of the discussion.

velocity of said tank in relation to velocity of rock

I'll shake the hand of any tank that hits a speed anywhere close to relevant in this context. Simply put, driving a tank at, say, 50MPH isn't going to affect the calculations of a rock breaking the sound barrier multiple times much.

ballistic trajectory/motion

I'm actually curious what factors other than "rock moves directly towards the tank" could be involved here/ Screwball?

and a few other minor factors..

Miscellaneous is the largest category.

[Kellhound]

Then there's no way in hell anything the size of a small projectile that'll go through the frontal armor of a tank.

It's a dumb place to aim.

Depends on how you define "small", the US APFSDS penetrator is only ~27mm in diameter.