TCS Daily

To Stop a Bullet

By Ralph Kinney Bennett - March 20, 2003 12:00 AM

American troops in the Iraq Theater of operations are equipped like no soldiers before them. From personal global positioning systems (GPS) to night-vision "monocles," they are bringing aspects of the "battlefield of the future" into reality. But one piece of technology of greater personal importance to the combat soldier than any other has roots extending back to ancient warfare - body armor.

U.S. Army and Marine frontline troops are wearing advanced body armor, far more sophisticated than the old "bullet proof" vests that some police and not a few gangsters began wearing in the 1930s. The ability of this new armor to withstand high velocity bullets and shrapnel from artillery and bombs (usually the biggest killer on a battlefield) is a tribute to the intensive development and adaptation of several synthetic "miracle" fabrics over the past 35 years.

These fabrics are the descendants of one of the more interesting developments of ancient armor - attempts to provide a kind of "soft" battlefield body protection that impaired body movement as little as possible. As early as 1500 B.C. soldiers in Mycenae were using a fabric armor consisting of 14 layers of linen. The Chinese later tried using layers of rhinoceros skin. By 500 B.C. chain mail was in use and Roman soldiers wore chain mail shirts in addition to bronze breastplates. Medieval Japanese warriors used a thick body armor made from densely woven silk.

After about two centuries of development culminating around 1400 A.D, the classic full suit of plate armor worn by the knights of medieval Europe was the state of the art in battlefield protection, gradually replacing chain mail. But advances in the power of bow weapons and then the rapid development of guns quickly rendered it ineffective. Indeed, starting around 1400, Swiss armies began to do away with armor because it was too cumbersome and impeded movement on the battlefield. In 1450, the Spanish introduced the harquebus - the first shoulder-fired gun - and the rest, as they say, is history. The musket and cannon ball and later the bullet and artillery shell brought a new level of lethality to the battlefield.

But the soldier's desire for protection, even against bullets, inspired various attempts to revivify body armor. Peddlers who followed the Union Army during the Civil War tried to sell crude vests containing cast iron plates to soldiers. They were so heavy that they soon exhausted the men who tried to wear them. Worse, the cast iron often shattered when hit by the large caliber bullets in use then, compounding the wounding effect.

Various types of armor, usually involving metal plates, were tried in the trenches during World War I. But before that, at the turn of the 19th century, the American military had explored and experimented with a type of soft body armor made (like the earlier Japanese armor) from tightly woven layers of silk. The thick, hot garments, which were very expensive to produce, proved able to withstand low-velocity bullets (flying at 400 feet per second), but by that time high-powered ammunition, traveling at 600 feet per second and higher, was being introduced.

The first wide use of body armor in modern times came with the "flak jackets" used by British Royal Air Force bomber crews in World War II. In 1942 these were essentially copied and issued by the U.S. Army Air Corps to its B-17 and B-24 bomber crews flying over Europe. Flak jackets had steel plates sewn into them. They were incredibly cumbersome and some aircrew preferred to just sit on them, bringing a new meaning to the expression "covering your ass." They could not stop a modern high velocity bullet but, as their name implied, they could stop shards of shrapnel from exploding German anti-aircraft shells.

Various types of body armor were explored in the post war era. By the time of the Vietnam War, soldiers and Marines wore heavy, bulky flak vests that offered some battlefield protection, particularly from grenade and artillery shell fragments.

In the 1960s, various law enforcement organizations, anxious to provide some sort of lightweight protection for on-duty police, began exploring various new synthetic fabrics that could be densely woven in such a way as to absorb the impact of a modern bullet. Around 1970 one of the most significant advances in body armor was made by coincidence. At that time, automobile tires were reinforced with "steel belts," actually bands of woven steel fibers. Dupont developed an even stronger substitute for steel - a new synthetic fabric called Kevlar. Army and law enforcement technologists obtained some Kevlar, folded it into several layers then fired at it at a rifle range. The stuff stopped bullets.

Over the next five years intensive testing in a joint effort by the military, law enforcement, the National Bureau of Standards and various government research laboratories determined the number of layers of Kevlar necessary to stop various caliber bullets. By the late 70s "are you wearing your Kevlar?" was a common question wherever police were on duty. Meanwhile, the military continued to refine its body armor to give troops protection against the high velocity bullets used in modern warfare.

The principle behind the body armor is the rapid dispersal of the energy of a bullet strike. Kevlar fibers (five times stronger than steel) are densely woven (you need a microscope to really see how densely), coated with a special resin and sandwiched between thin layers of very strong plastic film. Several layers of this Kevlar sandwich (depending upon how much protection is desired) are woven onto the inside of a military uniform fabric. These layers act as a sophisticated net - the ultimate safety net.

This microscopic net catches the bullet and begins dispersing its energy over a wide area. The force travels out over the entire surface of the armor along the thousands of Kevlar fibers. Ideally, although a soldier might be knocked down by the force of a round hitting him, the highly concentrated force that would otherwise allow the bullet to pierce his body will be dispersed as the bullet is caught in the dense Kevlar net.

Today, U.S. infantrymen and Marines are wearing the first truly bulletproof body armor, the so-called Interceptor system. It is also, at 16.5 pounds, the lightest weight system ever used. The Kevlar vest has detachable groin and neck guards and exceptional protection at the armpits - a frequent point of vulnerability in earlier armor vests. For increased combat protection, the vest has pockets front and rear in which the soldier can insert ceramic armor plates. These plates, much lighter than steel, also offer better protection. They can withstand a modern 7.62 mm. rifle round.

In the hellish atmosphere of an infantry firefight, safety is a highly relative thing. And although the precarious game of gaining an edge in either offense or defense will continue as long as there is warfare, today's body armor gives soldiers an extra measure of confidence and protection with minimal impairment of their mobility on the battlefield.

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