Goes Boom!

Here’s some tidbits of good news about restoring our industrial ‘boom’ capacity.
 
How much TNT explosive does the United States produce?  None. 

TNT is used to produce an array of explosive weapons including ammunition, bombs and 155-millimeter artillery rounds, but the military has been reliant on overseas sources.[1]

In a bit of good news, the Army is going to resume TNT production by building a new facility. 

As part of the Army’s quest to boost weapons production, it is reestablishing TNT production on US soil, inking a deal to build out a new facility in Graham, Ky.
 
“For the first time in decades, America will produce TNT on its own soil, manufacturing the explosive material our military uses for everything from hand grenades to 155mm artillery,” outgoing Sen. Minority Leader Mitch McConnell (R-Ky.) said in a press release.[1]

Boom!

As Army acquisition head Douglas Bush notes, control over our own explosives supply chain is vital. 

“[Restoring] TNT production gives us the ability to control and secure our supply chain for this vital component, especially in an era of increasing global challenges.”[1]

How could we ever have allowed such a vital industrial capability to vanish from our shores?  The military and civilian leadership that allowed this were derelict in their duty, if not treasonous for knowingly and willfully endangering America’s national security.  The military leadership should be recalled to active duty and court-martialed.
 
Setting that aside, the good news gets better … 

By fiscal 2026, the service is aiming to have the capacity to produce 100,000 rounds each month. To get there, Bush previously said the Army plans to spend $4.2 billion to build up the industrial base across various initiatives, to include commissioning three new domestic facilities to support 155mm production and a new metal parts production facility in Canada.[1]

Admittedly, I’m praising something that should never have been necessary and that's sad.  A country/military that doesn’t have its own explosives production capability is a fool and that’s exactly what we’ve been.  Still, it’s refreshing to see us begin to restore what we lost. 
 
I love being able to present positive posts.  It’s a shame that there are so few opportunities to do so, so enjoy this one!
 
 
 
_____________________________

 
[1]Breaking Defense, “Army inks $435 million deal for new TNT production facility”, Ashley Roque, 11-Nov-2024,
https://breakingdefense.com/2024/11/army-inks-435-million-deal-for-new-tnt-production-facility/

Explosive Effects

I didn’t want to address this but it keeps coming up and people keep getting it wrong so I guess I’ll have to.
 
Does anyone believe that a Mk82, 500 lb (192 lb of explosive filler) aerial bomb has a 25% larger explosive effect than a 16” high explosive (154 lb of explosive filler) battleship shell?  Of course not, and yet the Mk82 has 25% greater explosive filler weight.  Despite that, a 16” battleship shell has a profoundly greater explosive effect as demonstrated by the gigantic 50 ft diameter craters they leave.[5]  A Mk82 bomb is not to be sneezed at but it does not produce anything approaching that kind of effect.
 
Similarly, a Naval Strike Missile (NSM) has a 260 lb warhead which is 69% greater than a 16” battleship shell.  Does anyone believe that a NSM has a 69% greater explosive effect than a battleship shell?  Again, of course not!
 
So, the 500 lb bomb, with 25% more explosive, has far less explosive impact than a smaller (by explosive filler weight) battleship shell.  How can that be?  Shouldn’t the 500 lb bomb, with more explosive filler weight, produce a much greater effect than a battleship shell?
 
The answer/explanation is a combination of chemistry and physics.  Note, this is not a doctoral thesis and few of us are chemists or physicists so I’m going to simplify the following discussion for general audience comprehension.
 
 
Explosive Effect Definition
 
To begin, we need to define what an ‘explosive effect’ is.  There’s nothing magical or complicated about it.  It is simply the degree of destruction caused by the explosion.  A hand grenade has a small explosive effect compared to a 500 lb bomb.  See?  Nothing complicated.  But, if it’s that simple, how do we explain the bigger destructive effect of the 16” shell versus a 500 lb bomb that has more weight of explosive filler?
 
 
Chemistry and Physics
 
This is where we begin to delve into the chemistry and physics of an explosion (see Ref [6] for a detailed discussion of explosive chemical and physical properties).  Explosive effect is the damage inflicted on the target via a combination of overpressure (an instantaneous pulse of pressure far above normal atmospheric pressure), heat (the exothermic chemical reaction of the explosive), and physical damage by bomb/shell fragments (shrapnel), among other mechanisms.  Of these, pressure is the main destructive mechanism for general explosive munitions.  So, how is overpressure (increased pressure) generated?
 
We’ll answer that with a couple illustrative examples that lie at the heart of the matter and which we’ll keep referring back to.
 
Gunpowder – Gunpowder explodes, right?  Well, sure.  We’ve all seen hundreds of movies where barrels of gunpowder are ignited and explode.  Before we move on from this seemingly obvious phenomenon, let’s recall that we’ve also seen hundreds of movies where a trail of gunpowder, sprinkled on the ground, is ignited and slowly burns (acting as a fuse) rather than explodes.  Wait a minute, I thought gunpowder explodes?  Why does it burn on the ground rather than explode?
 
Gasoline – Gas explodes, right?  Or does it?  If gasoline, spilled on the ground, is ignited, what happens?  Does it burn or explode?  It burns!  However, if gas in a confined tank is ignited, it explodes!
 
Do you see the pattern – the key - behind this explode or burn phenomenon?  It’s confinement (containment).  When ‘explosive’ materials are confined/contained, they explode.  When they’re unconfined, they burn.
 
Now, what is it about confinement/containment that makes something explode rather than burn?  Again, it’s chemistry and physics!
 
Burning is actually a chemical reaction (oxidation).  A material reacts with oxygen at a very fast rate (an example of an exceedingly slow burning reaction rate would be rust!).  An explosion is the exact same chemical oxidation reaction but occurring in a confined/contained housing (the bomb or grenade or missile).
 
Let’s dig deeper.
 
When something burns, it undergoes a chemical reaction that releases gas as a byproduct.  In an open (unconfined/uncontained) environment – like gunpowder or gasoline on the ground – the released gas is harmlessly dispersed.  No damaging pressure build up can occur.  Conversely, in a confined/contained environment – like the inside of a naval shell – the released gas has nowhere to go and, as the burn continues and more and more gas is released, the quantity and, therefore, pressure of the confined/contained gas increases until, eventually, the pressure of the gas exceeds the strength of the container (the shell, bomb, grenade, or missile) and causes the container to burst which is the explosion we see.  This burst instantaneously releases the pent up pressure (now an overpressure wave) and heat.  In addition, the released pressure wave scatters the bomb fragments (shrapnel) and damage occurs to the surrounding area and objects.
 
The longer the pressure build up is contained, the higher the pressure gets inside the container and the greater the magnitude of the pressure wave when the container finally bursts and releases the pressure.  This is the overpressure blast wave which causes so much damage.  The overpressure wave causes objects around the explosion to be fractured, bent, twisted, ripped loose, and flung about.
 
Interestingly, if the container is stronger than the ultimate built up gas pressure, nothing happens.  This is what a bomb disposal chamber does.  It remains intact and contains the entire explosive force, releasing nothing.  The explosive gas can then be vented in a slow, safe, controlled manner.
 
Of course, the actual chemical composition of the explosive is important (different reaction rates, for example) but that’s beyond the scope of this post.
 
 
 
Shell versus Missile Construction
 
Now that we understand the importance of containment in producing an explosive effect, let’s examine the construction of various munitions.
 
Naval shells are intentionally constructed of very thick walls with relatively small burst charges of explosive material.  As we just discussed, the burst charge is greatly amplified by the containment of the heavy wall. 
 
Battleship 16” shells have wall thicknesses of around 3+ inches.  A 9.3 in diameter naval shell (type/gun unspecified) had a 2.5 in thick wall.[2]  And so on.
 

16" Battleship AP Shell Cutaway

16" Battleship HC (HE) Shell Diagram - note the shell wall thickness of 3+ inches

 
In contrast, a missile is, essentially, just thin sheet metal housing the fuel, motor, fuzing, and warhead.  For practical purposes, there is no amplification of the explosive weight.  The explosive weight is what it is.
 

Harpoon Missile Cutaway - note the thin sheet metal covering

 

We see, then, that the missile’s overall weight is consumed by fuel, guidance mechanisms, electronics, telemetry, sensors, fins and deployment mechanisms, and fuzes. A naval shell has nothing inside it other than a fairly simplistic fuze and, of course, the explosive chemical. All the naval shell's non-explosive weight goes into the wall thickness. Thus, a battleship’s 2000 lb weight is 154 lb of explosive filler and 1846 lb of wall.  That’s a lot of containment!  In contrast, the missile "wall" is nothing more than a sheet metal container.

Bombs lie in between shells and missiles and vary widely.  Some have heavy walls, though not generally approaching naval shells, and some do not.

Mk 82 Bomb Cutaway - note the reduced wall thickness compared to a naval shell

 
To sum up, missiles have thin walls that barely contain the burning gases before they burst. Thus, relatively less of the potential pressure buildup is achieved. Naval shells have thick walls that contain the burning gases and allow the pressure to build to its maximum potential before bursting. What's important is not the amount of explosive but the pressure at bursting.

 
Wall Thickness Effect
 
Understanding that, we’d now like to know how much of an effect wall thickness has on the explosive effect?  In a previous comment, a reader^[a] offered this rule of thumb relating containment wall steel thickness to explosive effect[7]:
 
Body Wall of 1" to 1.5" : Bursting Charge x 10 = Effective Explosive Weight
Body Wall of 0.5" to 1": Bursting Charge x 5 = Effective Explosive Weight
Body Wall of 0.25" to 0.5": Bursting Charge x 2.5 = Effective Explosive Weight
Body Wall of <0.25": Bursting Charge = Effective Explosive Weight
^[a]The reader offered this disclaimer:  “All figures are just from my memory, mind you, and shouldn't be taken as decisive fact (nor should any rule of thumb), but it is illustrative of the general idea.”
 
There are repeated references in discussions to equivalency charts between shells, missile, and bombs in terms of explosive/destructive effects but I’ve been unable to locate any.
 

Demonstrated/Explosive Effects
 
Here are some statements that qualitatively describe the destructive/explosive effects.  Of course, there are many factors that contribute to the observed effects of an explosion but these are illustrative, nonetheless.
 

The High Capacity (HC) [16”] shell can create a crater 50 feet wide and 20 feet deep (15 x 6 m). During her deployment off Vietnam, USS New Jersey (BB-62) occasionally fired a single HC round into the jungle and so created a helicopter landing zone 200 yards (180 m) in diameter and defoliated trees for 300 yards (270 m) beyond that.[5]

“The crater from a 500-lb. bomb with impact fuze (e.g., MK 82) is typically 30 feet in diameter and 15 feet deep (this obviously varies greatly with the terrain)” (Doleman Jr., Edgar C., 1984. Tools of War. Boston Publishing Company, Boston)  ;  note: this quote is unverified by me but the book exists and there is no reason to doubt it

A conventional 155mm artillery high explosive (HE) shell often produce a crater about 1.2–1.5 meters deep and 4–5 meters wide (4).  The M114 howitzer of WWII used an HE shell with around 15 lb of explosive.  The modern 155 mm M795 shell has around 24 lbs of explosive.

A 16-inch (406 mm) shell fired from an Iowa class battleship created a crater about 6 meters deep and 15 meters wide (4)

 
 
Summary
 
We now understand why a 16” battleship shell, despite having a smaller burst charge than a Mk82 500 lb bomb, produces a much greater explosive/destructive effect.  It’s all about containment!  The containment effect – or lack, thereof - is even more pronounced for missiles which, due to their almost non-existent containment, release their exploding gases at far less pressures and produce far less damage effects.
 
So, why don’t we build missiles with thick walls?  The answer is obvious.  The missile is a powered, flying object and every pound of extra weight decreases the speed and range of the missile.  A missile with, say, a battleship’s 3+ in thick walls would have a range of just ten feet!
 
 
Disclaimer:  I offered this disclaimer at the beginning and I’ll repeat it.  This was a simplified discussion to illustrate the basic concepts.  It was not intended to be a rigorous doctoral thesis or all-encompassing textbook.
 
 

 
______________________________________

 
[1]NavWeaps website,
http://www.navweaps.com/Weapons/WNUS_61-62_ags.php
 
[2]https://books.google.com/books?id=mhdaAAAAYAAJ&pg=PA624&lpg=PA624&dq=naval+shell+wall+thickness&source=bl&ots=a9K2NAt5Ot&sig=-dR5AI9_uvTGcUnUr5fZ0gpAupk&hl=en&sa=X&ved=0ahUKEwjnrdTbo97aAhWItVkKHZsgDgYQ6AEIiQEwDQ#v=onepage&q=naval%20shell%20wall%20thickness&f=false
 
[3]Maritime website, “U.S. Explosive Ordnance”, OP 1664 Vol 1, 28-May-1947,  BuOrd,
https://maritime.org/doc/ordnance/index.htm
 
[4]Quora website, Duc Quyen,  retrieved 6-Sep-2018,
https://www.quora.com/How-large-would-a-detonation-from-a-800mm-artillery-shell-make-compared-to-other-munitions
 
[5]NavWeaps website,
http://navweaps.com/Weapons/WNUS_16-50_mk7.php
 
[6]Pacsci Emc website, “Properties of Selected High Explosives”, Robert Weinheimer
Published: 27th International Pyrotechnics Seminar, July 2000
https://psemc.com/resources/pyrotechnic-white-papers/properties-of-selected-high-explosives-rev/
 
[7]Navy Matters blog comment, Ray D., April 8, 2017 at 10:33 PM, Navy Matters comment, “Syrian Tomahawk Strike”,
https://navy-matters.blogspot.com/2017/04/syrian-tomahawk-strike.html