cann a bomb destroy a tank ?? when no direct hit?

[Roo5ter]

That's not possible.  Such a small amount of charge could never move a tank!  -Finkeren.

To be fair this is an eyewitness account and he did just have the piss shocked out of him from the blast.  Large blasts in a narrow street will rattle your brains.  Even if the Panther had just soaked up the hit it probably would have been incapable of firing back or firing back accurately.  Kinda hard to use sights that are misaligned or beat the !#@$ out of due to HE.

[unreasonable]

Standard HE doesn't have any sort of penetration increase due to velocity similar to how rounds with shaped charges always have the same penetration regardless of range

 

Yes it does - HE shells have a solid nose cone to house the fuze, Soviet 152 mm only had 6kgs of explosive in a 40 kg shell. All that metal does not suddenly stop in mid-air when the charge explodes, it is accelerated outwards but still has its original vector forwards as well.  So an HE shell exploding on contact with a steel plate will have the nose cone at least projected at the plate at it's original speed plus the acceleration from the charge going off. 

 

How fast does the metal fly after the shell explodes? By my calculation about 500 m/s if the shell was stationary given the large mass of the shell and the low HE charge - but it is not stationary. 

 

For a modern HE shell with a much higher proportion of weight in actual explosives, the fragments will be moving much faster after detonation, so any forwards momentum from the initial velocity would be pretty immaterial.

 

I agree there is no additional penetration from the blast alone.

[unreasonable]

That's not possible.  Such a small amount of charge could never move a tank!  -Finkeren.

 

To be fair this is an eyewitness account and he did just have the piss shocked out of him from the blast.  Large blasts in a narrow street will rattle your brains.  Even if the Panther had just soaked up the hit it probably would have been incapable of firing back or firing back accurately.  Kinda hard to use sights that are misaligned or beat the !#@$ out of due to HE.

 

Again I think you are missing Finkeren's point - this example was of a direct hit from a heavy shell. No-one is saying that this would not knock out a tank, even if it did not breach the armour, which it often would. The question posed by the OP is what is the effect of near misses.

 

Edit - note also that JSU-152s also had AP and bunker busting ammo available, which may have been what was used.

Edited March 7, 2017 by unreasonable

[-=PHX=-SuperEtendard]

To be fair this is an eyewitness account and he did just have the piss shocked out of him from the blast.  Large blasts in a narrow street will rattle your brains.  Even if the Panther had just soaked up the hit it probably would have been incapable of firing back or firing back accurately.  Kinda hard to use sights that are misaligned or beat the !#@$ out of due to HE.

 

Even with the whole confusion of the fighting, I don't think having the turret blown off the tank would be something you could mistake easily

[Finkeren]

That's not possible. Such a small amount of charge could never move a tank! -Finkeren.

This is precisely the difference between a direct hit and a close proximity hit. Just a feet or two of air between the tank and the detonation makes all the difference. That's what I've been saying all along!

 

You're attacking a straw man dude.

[LukeFF]

But, but...can a bomb destroy a crane?

[Finkeren]

About the question of at what ranges the shockwave itself will kill the crew of a tank. That's obviously a very complex issue with no easy answer, because there are so many variables at play.

 

Generally speaking, the human body is fairly resillient to shockwaves.

 

A 5 psi blast overpressure will rupture eardrums in about 1% of subjects, and a 45 psi overpressure will cause eardrum rupture in about 99% of all subjects. The threshold for lung damage occurs at about 15 psi blast overpressure. A 35-45 psi overpressure may cause 1% fatalities, and 55 to 65 psi overpressure may cause 99% fatalities. (Glasstone and Dolan, 1977; TM 5-1300, 1990)

For comparison: An overpressure of 5psi (which causes ruptured eardrums in just 1% of cases) is enough to cause wood framed buildings to collapse, and an overpressure of 12psi will cause the total destruction of most conventionsl buildings. Source: https://www.fema.gov/pdf/plan/prevent/rms/155/e155_unit_vi.pdf

 

If we take a look at this study: http://www.dtic.mil/get-tr-doc/pdf?AD=ADA286212 on human survivability to bomb blasts (for use in creating safety gear for bomb disarmament) shows an interesting phenomenon, which can be seen in the graph at p. 8: There is a very small range between the distance from the explosion that will cause 99% fatalities and the distance that will cause 1% fatalities. That means that the difference between almost certain death and almost certain survival is just a few feet. It is also worth noting, that based on the graph the lethal range of the shockwave from a 1000lb TNT detonation (not counting shrapnel, collapsing buildings and other things that usually kills people during a bomb blast) is around 100 feet (28m) for a completely unprotected person standing in an open field (meaning if you are standing completely unprotected just 30m from a 1000lb bomb going off and are somehow not hit by shrapnel or thrown into something hard, you are pretty much guaranteed to survive)

 

The conclusion of the paper is, that wearing rigid body armor (like the one seen in "The Hurt Locker") significantly increases the survivability of the blast as opposed to soft body armor which only offers protection from shrapnel. This would indicate, that sitting in a tank would protect you quite well from not just shrapnel and fragmentation but also from the shockwave itself.

 

It's not conclusive but certainly worth discussing.

Edited March 7, 2017 by Finkeren

[Finkeren]

If you have the stomach for it, you can take a look at this book on "Pathophysiology of Blast Injury and Overview of Experimental Data", which gives an idea of the kinds of injuries that would result from the shockwave from a bomb blast.

 

https://www.ncbi.nlm.nih.gov/books/NBK202251/

 

I have not personally read it all, but it seems, that the kind of lung damage, which sets in at relatively low incident overpressure, and which might be fatal over time, would likely not be immediately incapacitating to a tank crew. Meaning that a tank crew might well sustain injuries from a close proximity blast, which will ultimately kill them but would not incapacitate them right away and thus won't result in a tank "kill" in the game.

Edited March 7, 2017 by Finkeren

[unreasonable]

I would just add that a 1,000lb bomb typically would have "only" about 500-600 lbs of HE filler - to get 1,000lbs + of explosives you are looking at something like the SC1000 kg bomb. 

 

Soviet 152 mm HE had about 6 kg of HE filler.

[Finkeren]

I would just add that a 1,000lb bomb typically would have "only" about 500-600 lbs of HE filler - to get 1,000lbs + of explosives you are looking at something like the SC1000 kg bomb.

 

True, but then again the standard WW2 bomb filler had a higher yield than plain TNT, right? Edited March 7, 2017 by Finkeren

[Gambit21]

...This would indicate, that sitting in a tank would protect you quite well from not just shrapnel and fragmentation but also from the shockwave itself.

.

That's my own common sense conclusion - no looking at links or studies or papers needed.

Thick armored box isolates you from your external environment this protects you from shockwaves - seems obvious.

 

Anyone ever wear ear protection while shooting?

Without? Same damn thing - you're isolating your ear drum from the sound/shockwave of the bullet - the explosion propelling said bullet rather.

Edited March 7, 2017 by Gambit21

[Finkeren]

That's my own common sense conclusion - no looking at links or studies or papers needed.

Thick armored box isolates you from your external environment this protects you from shockwaves - seems obvious.

 

Anyone ever wear ear protection while shooting?

Without? Same damn thing - you're isolating your ear drum from the sound/shockwave of the bullet.

I agree, but the more I study this topic the less I trust my common sense.

 

My common sense actually told me, that tanks in the game should be easier to kill with close proximity explosions. It was only when I started to look into it, that it turned out, that this apparently is not the case.

 

I suspect, that the sheer weight of the tank might also provide part of the protection, absorbing or reflecting a lot of the energy from the blast, but my knowledge of physics is far too limited to know if that's the case.

[Gambit21]

It's whether or not the metal of the tank transmits the shockwave outside to the air inside - not so much. Whereas water is extremely efficient at this. That's more or less how depth charges work.

 

When my 300 gallon goldfish pond freezes over in the winter I can't break the ice with a hammer - the shockwaves will kill the fish.

 

If you were submerged in a water filled steel container (with scuba gear on . ) and that container was itself submerged, and a depth charge went off nearby. You'd likely be in very poor shape even if your "tank" was unmarked. Depending of course on the thickness and materials involved.

 

Air is poor at transmitting vibrations - water very efficient.

Edited March 7, 2017 by Gambit21

[Finkeren]

The notion that the diffence in distance from a 1000lb TNT explosion that will result in 100% certain death and the distance that has 0% chance of killing you is as little as 10 feet also flies in the face of my common sense too, but apparently, that is how it is (Again looking only at the shockwave itself, not taking into account shrapnel, collapsing buildings, getting thrown into hard objects etc which are far more likely to kill you at far longer distances)

[Finkeren]

It's whether or not the metal of the tank transmits the shockwave outside to the air inside - not so much. Whereas water is extremely efficient at this. That's more or less how depth charges work.

 

When my 300 gallon goldfish pond freezes over in the winter I can't break the ice with a hammer - the shockwaves will kill the fish.

Off the top of my head, shockwaves should travel much better through metal than through the air (example: you can "hear" a train approaching from much further away by putting your ear onto the railroad track)

 

I think it's the transition from air to metal and back to air that provides the protection.

 

Again: I'd really like to hear from someone with greater knowledge of physics than myself.

[Roo5ter]

 So an HE shell exploding on contact with a steel plate will have the nose cone at least projected at the plate at it's original speed plus the acceleration from the charge going off. 

Question.  If you are behind me and throw a baseball that travels at a constant 60 kmph and I swing a bat as it comes from behind me with enough force to project that ball to 70kmph assuming the ball was at a stationary state does it somehow go to 130kmph?

 

No. It does not.  Could it go a bit faster?  Yes, but you are talking about a difference that is very minor at best especially considering the blast not the actual fragments itself are the source of penetration for HE.  It most certainly does not work with the physics model you have attempted to create.

[Gambit21]

I think that's due to how quickly the shockwave dissipates Fink. Imagine trying to throw a crumpled piece of paper. It moves very quickly as it exits your hand but I'm quite safe a few feet away.

Off the top of my head, shockwaves should travel much better through metal than through the air (example: you can "hear" a train approaching from much further away by putting your ear onto the railroad track)

 

I think it's the transition from air to metal and back to air that provides the protection.

 

Again: I'd really like to hear from someone with greater knowledge of physics than myself.

Yes it's a matter of transmitting that shockwave (air not efficient) and the enclosed environment isolating you from the overpressure.

Edited March 7, 2017 by Gambit21

[Roo5ter]

Even with the whole confusion of the fighting, I don't think having the turret blown off the tank would be something you could mistake easily

 

This is precisely the difference between a direct hit and a close proximity hit. Just a feet or two of air between the tank and the detonation makes all the difference. That's what I've been saying all along!

 

You're attacking a straw man dude.

I never said the turret didnt blow off just stated the tank might not have moved and made a good natured joke at Fink which he certainly didn't take the best.  

 

Fink, if you think a few kg of HE exploding against X amount of armor is more significant than 250kg (roughly the yield from a 500kg bomb - not exact) exploding 6 feet away from X amount of armor, you are absolutely incorrect.

[Finkeren]

I think that's due to how quickly the shockwave dissipates Fink. Imagine trying to throw a crumpled piece of paper. It moves very quickly as it exits your hand but I'm quite safe a few feet away.

Yes, that is what happens to explosions in open air, because air is easily compressable, and that is also why shockwaves travel so far under water, because water pretty much cannot be compressed at all.

[Finkeren]

Fink, if you think a few kg of HE exploding against X amount of armor is more significant than 250kg (roughly the yield from a 500kg bomb - not exact) exploding 6 feet away from X amount of armor, you are absolutely incorrect.

Yes, that actually is what I'm saying, and I've tried to present evidence to support that case.

 

As I said: My common sense actually agreed with your position, but when I started reading studies on the subject, I came to the conclusion, that I was wrong.

 

I'd like to exanine your evidence, if you'd show me.

 

EDIT: Just to be clear: A 1000lb bomb going off just 6 feet from the tank, would no doubt destroy it in any case, though arguably the armor itself might be intact.

Edited March 7, 2017 by Finkeren

[Roo5ter]

I have enough experience with explosions to know that you don't need HE anywhere near to achieve penetration.  Uparmored HMMWVs can easily be destroyed by much smaller blasts than these bombs at distances you think are irrelevant.  Panzer 38t for instance has 8-30mm armor per wikipedia and the uparmored HMMWVs range from more than 8mm to less than 30mm from rear wall to underneath and front firewall and sides.  The trick to avoiding penetration from HE was to go really really freaking fast so it would spread the blast a small amount and not allow it to focus on a single point in the armor.  Well, at least until the pressure plates came along.  
Imagine a HMMWV with a hand grenade taped to the side of it.  M67 has under a half lb of comp B.  I would much rather have that explode and be inside the HMMWV than a 150 lb bomb go off 4 feet away.  Any-freaking-day.  Do I have science to back it up?  NOPE.  Don't need it because I have been around enough explosions and less than friendly middle eastern theatres to nope the f#$k out of that one.  

Also destroying your claim is the fact you literally said that armor can reflect blasts.
No.
We are not discussing reactive armor.  What evidence can you provide that supports your latest theory that a static piece of steel can reflect a blast?. 

[Roo5ter]

Just for reference, Finkeren thinks that this explosive yield against armor

 is more effective than this explosive yield 15 feet away

 

[Finkeren]

Also destroying your claim is the fact you literally said that armor can reflect blasts.

No.

We are not discussing reactive armor. What evidence can you provide that supports your latest theory that a static piece of steel can reflect a blast?.

The very fact that any hard surface will reflect a shockwave to some extent. What do you think an echo is?

 

Take a look at the studies I posted a few posts back. Both go into significant detail about what difference it makes when a bomb goes off close to a large vertical surface such as a building: It greatly amplifies the effect of the explosion, because the surface reflects part of the blast back in the opposite direction.

 

How much of the energy of the blast will be reflected in this way from a tank? No idea, but it's not zero.

[Roo5ter]

No, it DEFLECTS the blast in any direction but that.  The same way that if you aim a fan at a wall the wind just rolls whichever way it can.  The blast takes the path of least resistance but the more pressure generated from the blast the more easily it is going to push through armor than be deflected into the middle of an already heavily overpressured area.  It isn't amplifying anything simply redirecting the forces involved until the object fails.   

[Finkeren]

Just for reference, Finkeren thinks that this explosive yield against armor

 

is more effective than this explosive yield 15 feet away

 

 

15 feet? Nope. In that case both will result in the tank being destroyed.

 

In the first case it'll primarilly happen through spalling. In the other case it might happen in a lot of different ways.

 

Again, your argument simply seems to be: "Look how big a boom a 1000lb bomb makes and look how much dirt it's throwing up. Surely that must be lethal to a tank?"

[Gambit21]

Reactive armor reacts to a penetrator and deforms/disrupts it. At least according to an article I read on it years ago.

Edited March 7, 2017 by Gambit21

[Gambit21]

...also I think Fink means "deflect"

[Roo5ter]

Where are you seeing that an HE explosion, not HESH or HEAT or any other shaped or tandem charge is causing significant spalling?  I don't think anyone has brought up an explosive charge flattened against the target in any manner similar to hesh.  Sitting a small explosive charge next to a tank is not the same as a flattened charge spread out over the armor.

[Finkeren]

No, it DEFLECTS the blast in any direction but that. The same way that if you aim a fan at a wall the wind just rolls whichever way it can. The blast takes the path of least resistance but the more pressure generated from the blast the more easily it is going to push through armor than be deflected into the middle of an already heavily overpressured area. It isn't amplifying anything simply redirecting the forces involved until the object fails.

You are right in that deflection is a more appropriate term, but it doesn't change what's happening: Energy from the detonation is directed away from the armor.

 

Also: I never said, that it amplified the explosion, I said it amplified the effect of the explosion in a certain direction.

Where are you seeing that an HE explosion, not HESH or HEAT or any other shaped or tandem charge is causing significant spalling? I don't think anyone has brought up an explosive charge flattened against the target in any manner similar to hesh. Sitting a small explosive charge next to a tank is not the same as a flattened charge spread out over the armor.

Yep, HESH is more effective at creating spalling, but that doesn't mean spalling doesn't occur in the other case.

[Roo5ter]

Yep, HESH is more effective at creating spalling, but that doesn't mean spalling doesn't occur in the other case.

Where are you seeing that small charges of HE are causing spalling on anything not made of tin?

[Finkeren]

Where are you seeing that small charges of HE are causing spalling on anything not made of tin?

Define "small".

[Roo5ter]

15 feet? Nope. In that case both will result in the tank being destroyed.

 

In the first case it'll primarilly happen through spalling. In the other case it might happen in a lot of different ways.

 

Again, your argument simply seems to be: "Look how big a boom a 1000lb bomb makes and look how much dirt it's throwing up. Surely that must be lethal to a tank?"

Referring to a video of a 5kg non shaped charge I posted you mentioned the HE charge would destroy the tank primarily through spalling.

 

[Finkeren]

Referring to a video of a 5kg non shaped charge I posted you mentioned the HE charge would destroy the tank primarily through spalling.

 

Not if you just place it on top of the tank. Probably not.

 

But if you shoot it out say a 152mm gun and it hits the tank at several hundred meters per sec, then yeah.

 

That's what the Su-152/ISu-152 did.

[unreasonable]

True, but then again the standard WW2 bomb filler had a higher yield than plain TNT, right?

 

No - they were either TNT or something like Amatol, which is a TNT+ammonium nitrate blend, or a TNT/Amatol.  Amatol has less explosive power than TNT, but is much cheaper!

 

There was another filler - RDX - that was stronger than TNT but it was only generally used in special cases like depth charges, being made in much lower quantities. 

[unreasonable]

Question.  If you are behind me and throw a baseball that travels at a constant 60 kmph and I swing a bat as it comes from behind me with enough force to project that ball to 70kmph assuming the ball was at a stationary state does it somehow go to 130kmph?

 

No. It does not.  Could it go a bit faster?  Yes, but you are talking about a difference that is very minor at best especially considering the blast not the actual fragments itself are the source of penetration for HE.  It most certainly does not work with the physics model you have attempted to create.

 

Not my physics model, old chap, just physics. If you carried out your experiment on the moon, then yes that is what would happen, provided that you applied the same acceleration to the moving ball as the stationary one - as an explosive charge inside a shell would do.  The only difference in the shell vs tank case is air resistance, but this takes place over time and so would have little effect in the fractions of a second in which fragments will contact the tank, so adding up the velocities is a reasonable approximation. 

 

Have a look at this site and look at the distribution of fragments from an exploding HE shell - you will see that the direction of travel makes a large difference to where the fragments go.

 

http://nigelef.tripod.com/wt_of_fire.htm

 

As to this particular case, use the Gurney equations to estimate the velocity at the explosion - you will find that the fragments' initial velocity is at most twice the speed of the projectile, because the ratio of HE to shell weight is so low.

 

edit - Going as fast as you can in a vehicle might make you feel better but has almost zero effect on the effectiveness of the explosion -  speed of vehicle = 50 mph = 22 m/s, speed of fragments 500-1,000 m/s, blast even faster. 

Edited March 8, 2017 by unreasonable

[unreasonable]

Where are you seeing that small charges of HE are causing spalling on anything not made of tin?

 

WW2 sticky bomb contained 1/2kg of nitroglycerin. Effective against armour upto 25mm.  Hawkins grenade, 1/2kg TNT.  Both had to be in contact with the armour plate to work.

[unreasonable]

...also I think Fink means "deflect"

 

What ever he meant it is a simple fact that blast waves - like any other kind of wave - can be reflected. If by "deflection" you simply mean reflection at an angle other than 180 degrees, then this what would usually happen due to the complex shapes and angles involved, but reflection is what it still is.

 

Since I obviously have some credibility problems in this thread a wiki quote.....

 

Effects of blast loads on buildings[edit]

Structural behaviour during an explosion depends entirely on the materials used in the construction of the building. Upon hitting the face of a building, the shock front from an explosion is instantly reflected. This impact with the structure imparts momentum to exterior components of the building. The associated kinetic energy of the moving components must be absorbed or dissipated in order for them to survive. Generally, this is achieved by converting the kinetic energy of the moving component to strain energy in resisting elements.^[18]

[Roo5ter]

WW2 sticky bomb contained 1/2kg of nitroglycerin. Effective against armour upto 25mm.  Hawkins grenade, 1/2kg TNT.  Both had to be in contact with the armour plate to work.

You mean the sticky grenade that used glue to adhere to a surface while also flattening on contact and therefore irrelevant to the discussion or are you talking about a different type of sticky bomb that is similar to a simple HE charge?

 

Hawkins grenade 'Multiple grenades were often used to destroy tanks or disable their tracks, and the grenade could also be used as a demolition charge.'  'When sufficient grenades were grouped together, they were capable of disabling a medium tank.'

The Hawkins grenades were not some sort of powerful charge obviously.  Browsing some sources it appears these were mainly used to disable tracks, NOT to penetrate armor.

[unreasonable]

You mean the sticky grenade that used glue to adhere to a surface while also flattening on contact and therefore irrelevant to the discussion or are you talking about a different type of sticky bomb that is similar to a simple HE charge?

 

Hawkins grenade 'Multiple grenades were often used to destroy tanks or disable their tracks, and the grenade could also be used as a demolition charge.'  'When sufficient grenades were grouped together, they were capable of disabling a medium tank.'

The Hawkins grenades were not some sort of powerful charge obviously.  Browsing some sources it appears these were mainly used to disable tracks, NOT to penetrate armor.

 

They are not irrelevant to the discussion - the whole point is that the sticky bomb had to stick: if it did, it was effective against light armour. If it went off without sticking, it was unlikely to do anything. The Hawkins was a very light charge, obviously it is only going to affect thin armour or knock off a track, but to do so it had to be in contact with the target. 

 

But in both cases the point is that contact massively increases the effectiveness of the blast effect, mainly because this creates spalling.  This is just to illustrate that the same principle that applies to HE shells: namely that direct hits are vastly more effective, also applies to these types of hand delivered weapons which obviously have no kinetic element to aid fragment penetration.

[Scojo]

This thread isn't about direct hits.

 

As far as shockwaves, the blast wave hitting the tank isn't much different from you hitting the tank with your fist, or a large hammer. The only difference is that you're hitting it with air instead of something more solid.

 

How well does steel hold up to hits from even bullets? Very well and that's very high force over small area. The PSI on that is very very high. The PSI from a bomb blasts dissipates VERY quickly the further away from the center you get, and even with very large bombs, you're not getting PSI on the hull of the tank that comes close to what a bullet will be putting out.

 

Now you obviously don't need to penetrate a tank to render it destroyed, however the PSI needed even to deform critical parts or cause spalling would be very high compared to what you'd get from a shockwave of a bomb that didn't explode very close by.

 

It's not surprising that a bomb blast several yards away would have little affect on a tank unless you get to extremely high weight bombs.

 

Just take a look at the Mythbusters episodes on shockwaves. The drop in PSI of the shockwave drops tremendously every inch away from the bomb it gets.

 

Like I said before, there's a reason why the ideal AT weapon has almost always been shaped charges with penetrators post WWII. And even in WWII. Wasn't the Panzerfaust a shape charge? And those killed more tanks directly than aircraft attacks did.

Edited March 9, 2017 by 71st_AH_Scojo