You read that title line and said:
"This bald headed mug has done up and lost his damn mind! Ain't no way that can happen..."
Well...
If I lost my mind, it was probably a few minutes after birth because I've been kinda off for as long as I remember.
Yes... Way... It can happen.
Let's look at the two ways that a bullet kills.
Penetrating Trauma
Blunt Trauma
The armor plate DOES stop the penetrating trauma where the projectile punches in and the fluids, soft tissue, bone, organs, and all that other fun stuff acts as resistance to slow it or stop it and absorb it's kinetic energy. Your armor, if it works, DOES defeat penetrating trauma, which is FAR more lethal and far more likely to cause you to cease all function than blunt trauma is...
Blunt trauma is that trauma that is received when the round is stopped by the plate... and with that, we expand.
First of all, the projectile is moving (obviously...) at a high rate of speed. It has mass of some form... even if it's only 50 some grains... Now, anyone who understands even the most rudimentary physics knows that Mass multiplied by Velocity equals Force. They also understand that an object in motion remains in motion until acted upon by an outside force. We also know that any kinetic action has an equal and opposite kinetic reaction.
OK, with the physics overview in order, let's look at how that flashback to high school relates to the modern battlefield....
First off... I want to say that I am NOT a medical professional.
I'm just one of those guys that knows enough about medicine to be dangerous to myself.
CPR/AED is about all I got medical wise...
So the following is purely for educational purposes, and hoping that someone who knows WAY more about this stuff than me chimes in!
"CRACK!"
If you've heard the sound, you've never forgot it.
You just took a slug in the plate.
In a micro second, there's been some serious physics going on here...
Assuming you're wearing a ceramic plate, when the round hit you, it pierced the carrier and impacted the strike face. When it hit the strike face, the ceramic material of the plate started to crack around the slug. The projectile continued, steadily being slowed by the friction of the crushing ceramic material that is effectively encasing the round as it slows. The kinetic energy of the round is absorbed by the plate as that friction of the slug and the ceramic fragments is effectively absorbed by the plate. These plates work by absorbing the slug's KE until it comes to a stop. Yes, it's hard. Yes, it's harder than most slugs. But it works by cracking and allowing the projectile to slow, as opposed to stopping it dead in the water.
A steel plate, on the other hand, relies on being hardened, harder, and stiffer than the projectile to stop it. When the round impacts the plate, either the slug flattens against the plate or it is shattered by the impact. We all know that spall can be a major killer. That's penetrating trauma anyway, and not relevant to this article. When the round hits the plate, the plate dimples and the round keeps pushing against the plate, any soft armor, and the body behind that until it comes to a stop.
This brings me to a particular medical condition... Called "Cardiac Tamponade."
This condition is a result of pericardial effusion, which is the pericardial sac filling with fluid at a rate faster than the sac can stretch. This causes pressure on the heart itself causes a reduction in the amount of blood the heart can pump with each stroke and it gets progressively reduced with each beat. Eventually, the heart's movement is so restricted that it can no longer pump enough blood to sustain life. Cardiac tamponade is the name for this pressure.
Typically, the pericardial effusion that causes this condition is caused by penetrating or blunt trauma to the chest (WINNER for this article), after heart surgery, percarditis, or some form of aortic or myocardial rupture.
How does this happen when a plate stops a round?
Again, this will typically involve a steel plate and it's why I stress so much that if you must wear a steel plate, wear a soft armor backing...
Remember how we discussed that plate moving back against the body until the slug stops?
Well, the greatest force is the center of the impact... And that is pushing against the chest.
This is like a very stout, hard punch... only harder and much faster.
How many of you have got punched?
If you said "No," You're either a bold-faced liar or you haven't lived a fun life...
(What? I'm the only guy around here who doesn't mind a good scrap every once in a while?)
Every time I've been punched, there's been a bruise...
What's a bruise?
Burst blood vessels, right?
And blood is a... what... again?
A fluid.
The capillaries are all over the body, including in the area of the pericardium.
The Pericardium is the sac that the hear rests in.
So when you get this nice, hard, fast impact... if the impact is absorbed SOLELY by your body... that kinetic energy has got to go somewhere... and it will... into your body... just like that punch...
So you get a deep bone bruise on a bone or a deep bruise in another muscle... It gets REALLY black, right?
That's A LOT of blood released into that vicinity.
A hit like a rifle round impact on your plate, WILL cause a deep bruise. If it's on the sternum or fractures a rib just right (I guess "wrong" would be a better word for this one?) the sternum and the pericardium under it will be compressed and that fluid has got to go somewhere...
Look at a bag of water...
Go fill a ziploc bag up with water...
OK, now push on it...
Water is displaced and moved, was it not?
Now... Push it hard... Like you mean it.
Bag broke, didn't it?
Same thing happens to your body.
So... If you don't choose your armor well, you CAN be killed by the bullet your armor stopped.
I'm not in any way suggesting that if you wear steel plates this is going to happen.
I'm not in any way suggesting that if you wear ceramics this won't happen.
I am saying that if you wear JUST plates this is MORE LIKELY to happen, and EVEN MORE SO if you wear just steel plates.
So let's look at what can be done about it...
In the field, Not much unless you're an 18D, ParaRescue Medic, 68W, Corpsman, etc... And I'm not sure they're equipped for it, though I do know a former USAFSOC surgeon who has treated it in the field early in OEF... My dad works with this man is also now employed as a very highly respected thoracic surgeon at our local hospital now...
Indicators include tachycardia (a really fast heart rate), distant or muffled heart sounds (stethoscope), jugular vein distention, and falling blood pressure.
So...
Take heed.
Choose your armor well.
If you choose good stuff, this is a non-issue.
If you choose crap, do so at your own peril.
Wikipedia link for more info on Cardiac Tamponade:
http://en.wikipedia.org/wiki/Cardiac_tamponade
Shameless video plug to my YouTube video on body armor:
http://www.youtube.com/watch?v=NlNIqUfGnwM
Stay Safe, Stay Frosty, Stay In The Fight!
V/R
-Kenny Smith
Chief Master Instructor
President, Total Force Training Group