Tuesday, October 25, 2005

Everything Old is New Again

Some time around the turn of the first millenium, a type of armor known as scale mail came to be worn by the Roman Legions, the Byzantine armies... just about any fashionably dressed and well equipped soldier of an organized army.

The Roman implementation of scale mail was called the lorica squamata, and consisted of about 1" x 2" rectangular bronze plates, heat treated (as much as bronze can be), shaped into scales, and dished with a rolled lip to increase strength. The plates were riveted to thin flaps of leather, which were in turn riveted through another layer of leather and padding.

The end result was a quite strong, flexible, and reasonably lightweight and comfortable armor, which was quite effective against slashing cuts. Unfortunately it was only moderately effective against piercing thrusts from swords; and quite poor against crushing blows, and strong piercing thrusts from spikes, axes, spears and the like.

Oh well, you can't have it all right...

Fast forward to the 9th century, and the concept is repeated in ductile iron, which was heavier, stronger but more likely to crack, somewhat less flexible, but otherwise more effective than the earlier lorica squamata.

This scale mail was worn over thickly padded, quilted jackets, constructed in layers. The jacket itself was effective enough as armor, that it was generally issued to less "expensive" troops, and those who were behind the front line of battle (like archers).

The use of scale mail as a primary armor form lasted into the 12-14th centuries, when the metallurgy of weapons, and the earliest introduction of man portable firearms; required heavy plate armor for primary protection. For areas requiring flexibility or less protection however, scale mail remained current until the early 17th century, when armor as a whole was obsoleted by the wide adoption of firearms as military weapons.

Fast forward again to the early-mid 20th century, and folks are looking once again to protect those in combat from the horrors of new weapons technology. The machine gun, artillery, grenades, and anti-aircraft had escalated mass casualties to truly horrific levels, and understandably the concept of armoring combatants came back to the fore.

Unfortunately, technology wasn't up to the task of providing full armor protection against high velocity bullets; but they COULD protect against shell fragments, shrapnel, spalling etc...

The fun part though, they chose to do it with... wait for it...

Ayup, scale mail.

This version of scale mail consisted of hardened aluminum (or in some of the earlier implementations steel) plates sewn into canvas pockets over a kapok or other densely padded jacket. It didn't do much to protect against bullets, but it was half decent against ricochets, shell fragments, and the like, as it was designed to do.

From the first implementations in the WW1 years, through WW2 and Korea, the technology was refined to the point where it could sometimes resist medium caliber pistol rounds. In the process the focus of armor developement changed from scale mail, into many overlapping layers of high strength synthetic fabrics; which by the time of Viet Nam, proved to be more effective at stopping medium velocity threats, and were easier for combatants to wear.

Of course soldiers on the battlefield face far more damaging threats than medium caliber pistols, so the powers that be looked for more effective ways to protect them.

Around the same time ('69), a pizza shop owner in Detroit named Richard Davis got shot. He didn't like being shot, and he didn't like cops getting shot, so he went looking for a way to give folks a "Second Chance", thus modern civilian body armor is born.

Initially soft body armor was constructed using ballistic nylon (thus the name) in up to 60 layers, but in '73 Davis's company Second Chance, started using Kevlar, and the rest is (very inaccurately reported) history.

Body armor comes in multiple levels as described in this chart:

Armor Level Protects Against
Type I
(.22 LR; .380 ACP)
This armor protects against .22 caliber Long Rifle Lead Round Nose (LR LRN) bullets, with nominal masses of 2.6 g (40 gr) impacting at a maximum velocity of 320 m/s (1050 ft/s) or less, and .380 ACP Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 6.2 g (95 gr) impacting at a maximum velocity of 312 m/s (1025 ft/s) or less.
Type IIA
(9 mm; .40 S&W)
This armor protects against 9 mm Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 8.0 g (124 gr) impacting at a maximum velocity of 332 m/s (1090 ft/s) or less, and .40 S&W caliber Full Metal Jacketed (FMJ) bullets, with nominal masses of 11.7 g (180 gr) impacting at a maximum velocity of 312 m/s (1025 ft/s) or less. It also provides protection against the threats mentioned in [Type I].
Type II
(9 mm; .357 Magnum)
This armor protects against 9 mm Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 8.0 g (124 gr) impacting at a maximum velocity of 358 m/s (1175 ft/s) or less, and 357 Magnum Jacketed Soft Point (JSP) bullets, with nominal masses of 10.2 g (158 gr) impacting at a maximum velocity of 427 m/s (1400 ft/s) or less. It also provides protection against the threats mentioned in [Types I and IIA].
(High Velocity 9 mm; .44 Magnum)
This armor protects against 9 mm Full Metal Jacketed Round Nose (FMJ RN) bullets, with nominal masses of 8.0 g (124 gr) impacting at a maximum velocity of 427 m/s (1400 ft/s) or less, and .44 Magnum Semi Jacketed Hollow Point (SJHP) bullets, with nominal masses of 15.6 g (240 gr) impacting at a maximum velocity of 427 m/s (1400 ft/s) or less. It also provides protection against most handgun threats, as well as the threats mentioned in [Types I, IIA, and II].
Type III
This armor protects against 7.62 mm Full Metal Jacketed (FMJ) bullets (U.S. Military designation M80), with nominal masses of 9.6 g (148 gr) impacting at a maximum velocity of 838 m/s (2750 ft/s) or less [provided the projectile hits the hard trauma plate insert]. It also provides protection against the threats mentioned in [Types I, IIA, II, and IIIA].
Type IV
(Armor Piercing Rifle)
This armor protects against .30 caliber armor piercing (AP) bullets (U.S. Military designation M2 AP), with nominal masses of 10.8 g (166 gr) impacting at a maximum velocity of 869 m/s (2850 ft/s) or less [provided the projectile hits the hard trauma plate]. It also provides at least single hit protection against the threats mentioned in [Types I, IIA, II, IIIA, and III].

Unfortunately, as in the 16th century, the thick multiple layers of cloth and padding STILL couldnt stop higher velocity, higher energy threats; and so hard breastplates had to come back AGAIN, as the trauma plate, which provides level 3 and level 4 protection.

A trauma plate is a hardened steel, aluminum, ceramic, or composite plate slotted into the ballistic vest to protect the vital organs in the torso, much as a 13th-16th century breastplate.

S0, the eternal cycle of armor vs. weapon has come around full circle once more, and...

Scale Mail is back again

We’ve been trying to get armor based on this concept out to the world for a while now. Obviously it’s an old concept, but it works.

Each of the plates is just a larger trauma plate in minature, and you end up with something like six times the total hard armor area of a trauma plate, at about half the depth.

The overlapping plates, which are technically a leaf mail style (basically the same as scale mail, only larger), have a few advantages. Most importantly (and most obviously) is the flexibility. More flexibility means more comfort, and longer wear time.

The two biggest advantages of the dragon skin (or other leaf/scale mail designs) from a ballistic protection perspective are that the small overlapping plates present multiple fracture planes to the incoming projectile, and that less area is compromised with a hit.

Factor one is directly dependent on the overlapping nature of the plates. When a single plate is struck, the energy of the impact is primarily expended within that plate, and the plate underneath it recieves only a small fraction of the total impact energy. If the plates are structures so that at rest there are two layers of protection in all locations, then the advantage is quite large. A side benefit of this, is the reduction of secondary injury (bruising, crushing, and breakage) from the projectile impact; though for some potential injury types in some cases this flexibility is a disadvantage (ribcage crushing injuries for example).

Factor two is the lesser compromise area. A strike in one area of the armor only compromises approximately 2”, whereas with conventional composite armor (soft armor with large front and back trauma plates) a single hit compromises the trauma plates completely (though that is changing), and at least 8” square of the soft armor area. Again, if the armor is constructed with full overlap, the secondary plate will still be in place to provide degraded protection in the strike area.

So we understand the plusses, what are the minuses? Weight, long term durability, and difficulty of manufacture (which means COST).

Of course to provide this level of protection means weight and cost. LOTS of weight and cost.

The best available current soft armor protection weighs from approximately 4lbs up to 7-8 lbs for a minimal coverage vest, at lvl 3a WITHOUT TRAUMA PLATES. When the coverage is extended to LVL 3, and includes pauldrons, spaulders, tasses, and a gorget/collar (full coat protection) that weight goes up between 12 and 18 pounds to a toal of 19-26 lbs (or more for some EOD armor, up inot 40+lbs)

For comparison, the new military Interceptor system is 16 lbs, the PASGT it replaced was 24 - both figures including front and rear trauma plates; and both are extended coverage vests not full coats.

The equivalent minimal coverage vest using leaf mail weighs about 18lbs, and the extended coverage vest weighs 22lbs, BUT it doesnt require the heavy trauma plates to reach lvl 3 protection, and in fact provides close to lvl 4.

With conventional vests, minimal trauma plate protection weighs about 2lbs for a hardened aluminum stab shield, and getting up to level 4 protection can add up to 16lbs, just protecting an area the size of a sheet of paper.

The absolute best technology we can come up with for full coat coverage lvl 3a protection with lvl 3 soft over the main torso, and lvl 4 trauma plates; weighs about 24-28lbs total (this is more coverage and more protection than current U.S. service issue personal armor).

That same coverage using leaf mail style armor can weigh over 30lbs, BUT it offers level 3 or better protection over the entire covered area, not just the trauma plate area; and approaches lvl 4 protection.

There is also a slight mitigating factor here, in that the weight is more evenly distributed, and the armor itself is far more flexible, which significantly improves the wearability and comfort of the armor.

I noted above the long term durability issue, but didnt elaborate. With smaller, thinner plates that slide over each other, there is the potential for mechanical wear, abrasion of the carrier, and a greater chance of a plate fracturing incidentally.

There is one more disadvantage to the scale design. If a bullet of the right construction, hits the right spot, at the right angle and velicity, it could be channeled in between the plates and into the wearer rather than expending itself in the plates. This is a very minor probability, but it should be mentioned.

Oh and heres the info on our current service armor:

Personal Armor System for Ground Troops

The PASGT was current until 2004 and is being replaced by the interceptor armor system:

Interceptor Body Armor

One should note, neither the PASGT nor the Interceptor offer that maximum level of protection I talked about above. Both are level 3a secondary protection with level 3 primary protection front and rear center torso; though new trauma plates are becoming available with level 4 protection. Unfortunately those trauma plates are very thick, very heavy, and VERY expensive.