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HE Effects on Armored Vehicles

 
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HE Effects on Armored Vehicles - 4/1/2013 6:16:55 PM   
jimcarravallah

 

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quote:

ORIGINAL: Arjuna

Harry,

re armoured units and arty fire. This is another one of those thorny issues that you can never satisfy everyone. If you reduce the impact of arty on AFVs in term of suppression and kills then you will get feedback that arty is not being given due effect. If you increase the effect then you get feedback like yours that armour cannot act aggressively enough. Their are historical facts, case histories etc to support both arguments. Arty did destroy tanks, it did cause units to bunker down or retreat. There are cases where the decision was taken to drive straight through and accept the casualties. So obviously there are a plethora of factors impacting on the decision. Eg commander aggro or judgement or the units recent engagements, the mission priority, the perception of danger and just plain old random effects. We try and factor all of these into the reaction code. Sure we can tweak these further but there must come a time when we say that on balance this is about right. My gut feel at the moment is that it is about right.

I'd be happy to hear from others on this though and I'm prepared to countenance some minor adjustments.


Evidence from the redesign of armored and tactical vehicles to counteract Improvised Explosive Devices (IEDs) indicates we've learned in the US that tanks or tactical vehicles don't necessarily need to be destroyed to be made ineffective in combat.

In some instances crews are made ineffective from severely shaking and / or bouncing them off the walls inside their armored cocoon / operator's stations by nearby blast concussions.

Given the design of armored vehicle operator stations and soldier protective gear for the World War II era, there's probably some room to allow for certain heavy bombardment / shell explosive load combinations to, as a minimum, demoralize armored formations and in some instances put vehicles out of commission because the crew is incapacitated by the concussive effects of blasts against a vehicle's weight (F = MA).

With the caveat that using calculus to get the right numbers to pass physics wasn't one of my strong points when I studied engineering , I'd guess the zone of demoralizing effect against armored vehicles is possibly the 100-percent kill range of shell effects for bombarding entrenched troops (to eliminate shrapnel as a cause for injury to troops in a buttoned up vehicle) and the vehicle disabling (by crew shaking injuries) is a subset of that range calculated from vehicle weight and shell explosive charge weight if pinpoint accuracy for the F = MA calculation against a specific vehicle is desired.


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jim
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RE: HE Effects on Armored Vehicles - 4/1/2013 11:24:25 PM   
Arjuna


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Jim,

In your formula what does F equate to and what does MA equate to?

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RE: HE Effects on Armored Vehicles - 4/1/2013 11:35:28 PM   
dazkaz15


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quote:

ORIGINAL: Arjuna

Jim,

In your formula what does F equate to and what does MA equate to?


Newton's laws of motion

Second law: The acceleration a of a body is parallel and directly proportional to the net force F acting on the body, is in the direction of the net force, and is inversely proportional to the mass m of the body, i.e., F = ma.

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

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RE: HE Effects on Armored Vehicles - 4/2/2013 1:50:45 AM   
jimcarravallah

 

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quote:

ORIGINAL: Arjuna

Jim,

In your formula what does F equate to and what does MA equate to?


Much as I'd like to take credit for it, the formula belongs to Sir Isaac Newton: Force = Mass times Acceleration.

The force would be the HE blast pressure effects of the shell measured in pounds per square inch or Newtons per square meter.

The mass would be the vehicle suffering the blast.

The acceleration would be how far the vehicle of that mass could move under the blast pressure effects.

Exploding close enough to its target, a 155mm HE Shell used as an IED can shake a buttoned up 70 ton armored vehicle enough to disable the crew even without damaging the armor. That same shell would affect a 50-ton tank crew in the same way at a greater distance from the blast center because of its lighter mass.

Here's some information on mine and IED effects that may help in developing a damage algorithm.

http://www.altairhtc.com/europe/presentations/session2/session02_segula_fallet.pdf

http://www.dynalook.com/international-conf-2002/Session_6-5.pdf

http://www.tass-safe.com/public/files/042010/occupant_responses_in_mine_blast-SAFE2009.pdf


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Take care,

jim

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RE: HE Effects on Armored Vehicles - 4/2/2013 11:04:54 AM   
RockinHarry


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quote:

ORIGINAL: jimcarravallah


quote:

ORIGINAL: Arjuna

Jim,

In your formula what does F equate to and what does MA equate to?


Much as I'd like to take credit for it, the formula belongs to Sir Isaac Newton: Force = Mass times Acceleration.

The force would be the HE blast pressure effects of the shell measured in pounds per square inch or Newtons per square meter.

The mass would be the vehicle suffering the blast.

The acceleration would be how far the vehicle of that mass could move under the blast pressure effects.

Exploding close enough to its target, a 155mm HE Shell used as an IED can shake a buttoned up 70 ton armored vehicle enough to disable the crew even without damaging the armor. That same shell would affect a 50-ton tank crew in the same way at a greater distance from the blast center because of its lighter mass.

Here's some information on mine and IED effects that may help in developing a damage algorithm.

http://www.altairhtc.com/europe/presentations/session2/session02_segula_fallet.pdf

http://www.dynalook.com/international-conf-2002/Session_6-5.pdf

http://www.tass-safe.com/public/files/042010/occupant_responses_in_mine_blast-SAFE2009.pdf



Thanks! Very good info! One reason more, to get out the steel coffins off blasted areas more quickly.

Does disabling crew mean kills/injuries, or just cases of temporary inconsciousness? Both?

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RE: HE Effects on Armored Vehicles - 4/2/2013 11:25:27 AM   
Lieste

 

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I'd note that blast loading is only relevant at extremely close distances (I think that the lethal distance for personnel for a 2000lb/900kg bomb is only of the order of 110 feet/ 33m). While a vehicle is much larger and may be subjected to higher loads, it is also less sensitive to low point loadings... so a distance with a similar magnitude is to be expected. A comparison with fragmentation is enlightening... personnel casualties are 'significant' to 400m and safety distance is over 1000m.

Smaller explosive devices have even less significant blast effects ~ while their fragmentation lethality remains relatively high.
Even though fragmentation 'distances' are high, the effects are typically highly directional ~ two 'branches' where the dense cone intersects the ground (and the area near it where distant personnel and vehicles are found)... This is better thought of as a wide but shallow 'rectangle' rather than as circular areas.

All fragments have differing values of mass and velocity, with the largest fragments remaining lethal to much longer distances ~ these drive the safety distance. The relatively low and reducing numbers of fragments of increasing lethal distance make the 'casualty radius' sensitive to anticipated target size and toughness, and this is mostly related to hit probability rather than lethal energies except for very short ranges where most fragments are light and fast moving, but rapidly losing their limited supply of energy... here hits are *nearly* assured, and toughness is more important to relative vulnerability (as it reduces the population of lethal fragments).

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RE: HE Effects on Armored Vehicles - 4/2/2013 1:04:20 PM   
jimcarravallah

 

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quote:

ORIGINAL: RockinHarry

quote:



. . .


Here's some information on mine and IED effects that may help in developing a damage algorithm.

http://www.altairhtc.com/europe/presentations/session2/session02_segula_fallet.pdf

http://www.dynalook.com/international-conf-2002/Session_6-5.pdf

http://www.tass-safe.com/public/files/042010/occupant_responses_in_mine_blast-SAFE2009.pdf



Thanks! Very good info! One reason more, to get out the steel coffins off blasted areas more quickly.

Does disabling crew mean kills/injuries, or just cases of temporary inconsciousness? Both?


In US Army logistics jargon, a disabled soldier is defined as one who must be removed from the battle after being stabilized from his injury.

The definition was used as one of the planning parameters for defining the number of medical personnel, medical treatment equipment, litters, injured soldier transport capacity, and injury treatment capacity assigned at various command echelons in the battle zone.

In today's treatment regime, being knocked unconscious is also considered disabling, but that is because medical science understands more about permanent brain damage caused by concussion than was understood in the World War II era.

For World War II era, I'd equate a blast that could cause crew unconsciousness the equivalent of the suppression / fatigue / morale penalties associated with bombardment instead of capable of disabling combat power during the remaining term of a typical scenario.

As an aside, Leiste is right, the blast loading damage is based on distance from the blast center, not any different from how the danger of fragmentation damage on soft targets diminishes with distance from blast center.

However, the once the distance is beyond the zone of the armor / vehicle skin being ruptured by the blast, the calculation should take into account vehicle mass instead of armored thickness for evaluating disabling capability.

What opened my eyes was discussion of Iraqi opponents using remotely exploded 155 mm HE rounds as tank killing devices along roads in Iraq. While it seemed logical the most severe casualties were to commanders who rode half exposed from a top turret while directing tank operations before being fired upon, it turned out that crew inside the tank would suffer disabling injuries from what amounted to ground burst shock even when protected inside the heaviest of armored vehicles in the US arsenal.

There is significant research going on right now to design seat dampening systems, crew compartment equipment configurations, crew compartment padding, and head protection equipment to counteract the blast concussion effects of rounds which were considered little danger from airburst damage in normal combat involving buttoned up vehicles yet were a crew danger from nearby ground bursts against the same vehicles regardless of the vehicle's protection configuration.




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Take care,

jim

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Post #: 7
RE: HE Effects on Armored Vehicles - 4/2/2013 1:28:33 PM   
Lieste

 

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Hmm, yes, but the IED is often several 155mm rounds, and is used as an on-route mine, often in a culvert. As an example this is more explosive than found in most AT mines, even in a single shell. The tamping effect of the ground and direct contact/extremely close proximity of the tank increases the effect of a given charge of HE compared to open air detonation at some slight offset/distance.

A direct hit from a 155mm HE round will fairly reliably disable any armoured vehicle, and is confirmed as causing difficulties for even something as large as a battleship ~ South Dakota was badly damaged by mostly 5 and 6" fire at Guadalcanal 2.

Tanks are relatively small, and although even a single round *can* cause a direct/damaging hit, it is typical that many rounds are needed to obtain a reasonable number of disabling hits on a formation.


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Post #: 8
RE: HE Effects on Armored Vehicles - 4/2/2013 2:43:44 PM   
wodin


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Concussion kills have been noted since WW1 onwards..many Germans where found in pillboxes in WW1 with not a scratch on them..dead from concussion.

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Post #: 9
RE: HE Effects on Armored Vehicles - 4/2/2013 6:09:06 PM   
RockinHarry


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The Churchill AVRE did the same on Germs in Siegfried line pillboxes and others.

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