Mk84 blast radius

[Kula66]

From memory 15000lbs ... I used an extreme example to demonstrate that all bombs aren't equal in frag/blast terms ... it all depends on things like the ratio of explosive to weight - which can be different

[Cobra360]

A Daisy Cutter is around 15,000lbs with 12,600lbs explosive.

[Yellonet]

It's just takes a bit of common sense to understand that the overpressure effect doesn't reach "very far".

 

If you think about the overpressure effect expansion as the expansion of a balloon when you inflate it, you can see that the balloon expands quite rapidly in the beginning (high overpressure) but the bigger it gets the slower it expands (low overpressure).

 

I know it's a bad analogy but I hope you understand what I mean.

 

BTW, 110 ft radius makes quite a large area.

110 x 110 x ~3.14 ~ 38,000 sq. ft

[tflash]

To come back to the Mk84, and again to the blast aspect, not the frag thing. The Mk-80 series of bombs was not made with fragmentation as a main goal, but primarily blast.

 

Suppose the lethal blast range is 110ft (ca. 30 meters) for an Mk84.

 

What would the be the lethal blast range of an Mk82, let alone Mk81? Are these just halloween toys only able to scare some kids?

 

If I'm not killed by the sheer pressure of a 2000-ponder, I wonder what a 500 pound weapon can do. No doubt I can just finish smoking my sigarette when an Mk-82 falls 10 meters from me?

 

But I agree the blast power in an open space will drop exponentially with range, so I think my 400 feet for an Mk84 is to much.

[GGTharos]

But the blast effect is never the main kill mechanism against infantry in most conventional weapons.

 

In any case, what the heck does that 110' radius represent? 100% lethality?

 

So what's the 50% radius? 200'?

[Yellonet]

To come back to the Mk84, and again to the blast aspect, not the frag thing. The Mk-80 series of bombs was not made with fragmentation as a main goal, but primarily blast.

 

Suppose the lethal blast range is 110ft (ca. 30 meters) for an Mk84.

 

What would the be the lethal blast range of an Mk82, let alone Mk81?

The Mk82 uses about 1/4 of the explosives of a Mk84, right?

So I would guess that the overpressure effect would be in a volume of 1/4 of the Mk84's overpressure volume, that means that the radius is more than 1/4 of the Mk84's radius... I think.

Or maybe you can't count like that.

 

Are these just halloween toys only able to scare some kids?

No, but they aren't really made to kill people, but destroying buildings, machines, bridges and so on.

 

If I'm not killed by the sheer pressure of a 2000-ponder, I wonder what a 500 pound weapon can do. No doubt I can just finish smoking my sigarette when an Mk-82 falls 10 meters from me?

No, you will most likely die.

 

But I agree the blast power in an open space will drop exponentially with range, so I think my 400 feet for an Mk84 is to much.

Yes.

[Yellonet]

But the blast effect is never the main kill mechanism against infantry in most conventional weapons.

 

In any case, what the heck does that 110' radius represent? 100% lethality?

 

So what's the 50% radius? 200'?

Good question, the page says "The effect of blast on personnel is confined to a relatively short distance (110 feet for a 2000 pound bomb)."

 

But if the 100% radius were 110ft the 50% radius should be maybe 140ft?

[GGTharos]

Yes, it's certainly not linear.

[Cobra360]

Here is a pic of a Mk-84 (left) and a new enhanced 1,000lb bomb (right) not Mk-83. If only there was an object to scale it against.

 

[Cobra360]

Explosion of Mk-82 Bomb taken from 1500m

 

[Yellonet]

Most of the power goes right down in the ground...

[Cobra360]

That would depend if a delay fuse was used or contact. Bombs with delay fuses will make a bigger crater than the same bomb on a contact fuse.

 

This is a 2,000lb LGB detonation.

[Yellonet]

That would depend if a delay fuse was used or contact. Bombs with delay fuses will make a bigger crater than the same bomb on a contact fuse.

 

This is a 2,000lb LGB detonation.

I was refering to your image of the Mk82 detonation.

[Cobra360]

I know you were Yellonet, I just wanted to show a 2,000lb explosion instead of a weak 500lb one. Relative of course.:D

[tflash]

Even though these pictures do not offer clear reference clues, I think I'm not the only one that would put his chances in a 110 ft circle. :=)

 

You guys are right the problem must be the definition of lethality. I can imagine that 110ft means 100% sure kill. I can live with that. At 200ft, you *might* not be dead, but only will never get on your feet again :=)

[Guest IguanaKing]

"Kill" in PK refers to rendering the intended target combat ineffective. It does not necessarily refer to the total destruction of equipment, nor does it refer to the actual death of personnel. The circle of lethality though, pretty much says, "if you are inside this circle, you WILL die". Outside that circle, your chances are not good, but you might make it. The PK=0 definition in the MSD refers to no troops being rendered combat ineffective. Inside that range, they can be wounded OR killed. We also have to consider the fact that detonations do not happen in a vacuum (figuratively speaking, of course ;) ), nor do they occur in a "sterile" environment. Debris from surrounding vehicles, structures, and yes, even personnel, adds to the frag effect.

[hitman]

Out of curiosity, have anyone thought of the decay rates between the said weapons explosive materials? I would have to think that semtex (not used ingame) has a higher decay rate than low grade uranium. Definately the exotic materials used in area denial weapons would have a significant decay rate...and create something called a precurser effect above ground if detonated at a lower altitude.

[MonnieRock]

Gentlemen,

 

I admire the scholar approach to this. Maybe someone that is a weapons expert for the military can help us a little here without giving out too much data.

 

Now, I do not see myself going out to the USAF bombing range and standing anywhere near 110 Ft from the point of impact of a Mk-84. Nor would I park my vehicle 110Ft from the point of impact and hope to drive away.

 

Maybe some of your physics nuts can chime in this. What is the effect of this pressure/heat on a fuel cell in an aircraft say ummm 100Ft from the point of impact?

 

In Lo/Fc it has always seemed strange to me the cluster bombs are far more leathal.

 

Another thought. So you get a direct hit on a tank with a Mk-84. Want about all the frags from the target that has been blown to pieces? What happends to it's weapons stores? Or, you get a direct hit on an aircraft. What is the effect of it's fuel load?

 

Thanks,

Monnie

[Weta43]

I said I'd have a go at working out a radius at which a 6 sq ft area would have a 60% chance of getting hit by a shard from a MK84 bomb if 80% of the steel turned into peices of various standard sizes, but I finished work before I got a chance. If anyone's interested: ( there's 2 columns here from an excel sheet, but the tab delimination hasn't worked...)

MK84

lb kg

Weight 2039 926.81818

Explosives 945 429.54545

Difference (casing etc.) 1094 497.27273

80% of casing as shards 875.2 397.81818

 

Steel kg/m^3 7850

Volume of shards from case (m^3) 0.0506775

 

Shard length (m) 0.05 0.025

Shard width (m) 0.02 0.02

Shard thickness (m) 0.015 0.015

 

Shard Volume (m^3) 0.000015 0.0000075

 

# shards from casing 3378.498 6756.9967

 

 

 

 

radius (feet) 51.85169 73.328597

 

Sphere's area (4*Pi*R^2) 33785.91 67570.42

 

sq ft per shard 10.00027 10.000067

 

In case this becomes indecipherable when I post it - if 80% of the 1094lb of casing turns into pieces 2.5cm x 2cm x 1.5cm (allowing for the nose, fuse & tail sections to get driven off as larger bits into the ground or air) you end up with 6757 peices, which, if they leave uniformly would mean that at at a distance of 73' from the blast a 6 sq ft area would have a 60% chance of collecting a piece (1 piece every 10 sq ft), or - 6 out of 10 people standing straight on 73' from the blast would get hit by shrapnel.

[SUBS17]

The reality is the bomb fragments don't break down into uniform pieces, they are in various sizes from a small chip to a large chunck that can split a person in half.

[Weta43]

I realise that, but every big chunk takes another from the equation & I was trying to get a best (largest) case for the 60% radius (or worst depending if you're giving or receiving).

 

I couldn't imagine it breaking up into more peices than if they were uniformly of 2.5cm x 2cm x 1.5cm & the less peices the more survivability 'cause you're less likely to get hit

 

If there are 6757 peices the 60 % chance radius for a 6 sq ft target is 73', but for 3378 peices it's only 52'.

 

With 80% of the case turning into peices with an average size of 2.5cm x 2cm x 1.5cm at 101' there's only a 33% chance of getting hit (4 out of 12 people will be hit)

[tflash]

Weta43, I think your approach is valid. We are trying to determine probabilities, and then your way of calculating the pieces makes sense.

 

Of course, we have a somewhat more complex phenomenon. but let's suppose we are in open field, and we have a fuzed detonation above ground;

 

I would think your model is OK, but we might try to take into account that the energy absorbed by the dispersion of the fragmentation mass has a negative effect on the blast radius.

 

Another "problem" seems to me the heat and its dissipation: I have no clue if the heat travels further then the overpressure? Or is is heat at the core - overpressure - then frag in a much wider radius?

 

Anyway, I have tgis gut feeling there is something cynical about a Mk-84-based JDAM to be called a "precision weapon" :) I think the term must have been coined from the release altitude's point of view. With all we have emerging from this discussion I would think an area the size of a soccer field would be a very unhealthy place for some moments after impact.

[Yellonet]

Heat does travel farther than overpressure.

[Guest IguanaKing]

 

Anyway, I have tgis gut feeling there is something cynical about a Mk-84-based JDAM to be called a "precision weapon" :) I think the term must have been coined from the release altitude's point of view. With all we have emerging from this discussion I would think an area the size of a soccer field would be a very unhealthy place for some moments after impact.

 

BINGO!!! Give that man a cigar. :D

[504 Wolverine]

In 1992 there was a 2000lb bomb that destroyed the Forensic science labs in East Belfast. The blast was heard up to 30 miles away and did a lot of damage to property (over 700 homes) up to 7 miles away.

 

I myself live 5 miles away from "ground zero" and I remember this incident clearly. Windows on the side facing the blast were damaged and the door flew open like someone kicked it in. I for one would not like to be within a mile of a mk-84

 

If I ever find the pic of the blast damage to the labs and area I will post it. The blast radius of 2000lbs of explosives is

amazing.