The shortage of effective armor for troops serving in Iraq borders on the scandalous. Body armor has been in such short supply that soldiers have been buying their own. Supplementary body armor packages that protect the arms and sides of the body began shipping only in May. Soldiers are draping their Kevlar vests over the sides of unarmored Humvees and using scrap wood and metal on the vehicle's floor for makeshift protection against roadside explosives. The army is scrambling to install steel doors and bulletproof glass on Humvees as quickly as possible, a move the Army Material Command estimates could reduce casualties by 25 percent. Some 4,500 Humvees are expected to be "up-armored" by the end of this month. Meanwhile, the army's vaunted new wheeled Stryker vehicles, though armored, may not be able to withstand the impact of a rocket-propelled grenade (RPG), a favorite insurgent weapon, and now sports an unwieldy add-on metal cage for extra protection.
"What's been highlighted in Iraq is how do you provide protection to people riding in wheeled vehicles," says Bruce Fink, chief of the materials division of the Army Research Laboratory (ARL). "Historically, we have not put a lot of effort into trying to protect people in wheeled vehicles because they weren't supposed to be in areas where they are under direct fire. But, unfortunately, that's the situation we're in--where we're getting a lot of direct fire at wheeled vehicles."
Indeed, the army lists both body armor and wheeled vehicle protection among its top 10 capability gaps. Helping to bridge that gap is a new type of add-on reactive armor jointly developed by Rafael Armament Development Authority in Israel and the General Dynamics' Armament and Technical Products unit in Burlington,Vt. Reactive armor is being added to tracked Bradley fighting vehicles as a counter to RPGs after its successful--and secret--use by Israeli defense forces for many years. According to a spokeperson for General Dynamics, reactive armor consists of 105 tiles that attach to the sides, turret and front of each Bradley. The tiles, which look like small boxes, contain a special explosive charge that detonates when hit by a missile or rocket with a shaped-charge warhead. The resulting explosion disrupts the incoming, armor-penetrating gas jet produced by a RPG, for example, so the Bradley remains unharmed. Upgrading Bradley fighting vehicles with reactive armor is a process that will continue for some time. Rafael and General Dynamics will produce 80 kits for the U.S. Army this fall in a deal worth $23.5 million and another 60 kits for $17 million by July of 2005.
Humvees and Stryker vehicles, however, cannot support the added weight of reactive armor. Just adding steel plating to Humvees places added strain on suspension and drivetrain systems not designed with armor in mind, putting those vehicles out of service more frequently than expected. The solution may be spray-on polymer armor now being developed by the U.S. Navy's Office of Naval Research (ONR). The spray-on armor is similar to a polymer commonly used as a spray-on truck bed liner. It's made from either polyurethane, polyurea or a mixture of the two. When applied to steel, the polymer spreads out the shock of an explosion and helps prevent impacted material from shattering. In tests, a 500-pound bomb detonated near two trailers obliterated the unarmored trailer but only buckled the walls of the trailer whose walls were coated with the rubbery polymer.
"The polymer is highly elongated so it acts like an invisible, protective net," says Roshdy Barsoum, the program officer in charge of the polymer project at ONR. "The aim is to use it on a vehicle to protect soldiers while keeping the added weight low enough so it doesn't affect vehicle maneuverability." The polymer reacts differently depending on the material to which it has been applied. The reaction is also complex in that the polymer halts momentum while also transforming itself from a soft to hard material.
Adding the spray-on polymer to Humvees would cost about $10,000 a vehicle, which is still a much cheaper and more lightweight alternative to steel plating. The polymer is also simple for soldiers in the field to apply--it would be as easy as lining the bed of a pickup truck, Barsoum comments. The Pentagon has not decided whether to apply the polymer on Humvees just yet owing to a potential drawback: because the polymer is an insulating material, it may increase the temperature inside the vehicle if applied to the outside. Conversely, if the polymer is applied inside the vehicle, ventilation may be compromised.
Individual soldiers, meanwhile, may get some added protection from a shear thickening fluid (STF) applied to fabrics like Kevlar. Hyped as "liquid armor" by some, the STF doesn't actually stop bullets but is very good at resisting stabs from knives and other sharp objects, according to ARL's Fink. "An ice pick easily penetrates Kevlar fabric," he says, "but I haven't yet met anyone strong enough to knock it through STF fabric."
STF, which is made from polyethylene glycol, acts like a liquid until it comes into contact with a penetrating object like a knife. The STF then stiffens to a more rigid material that resists penetration. When applied to body armor, STF can reduce the thickness required for protection, thereby providing the wearer with more flexibility of movement. In addition to its use by soldiers, STF fabric may become a staple of prison guards and police officers. Fink thinks it could also be used for tires or products like ski boots given that STF fabric is initially flexible but stiffens under increased strain.
Fink furthermore has high hopes for what he calls ceramic chain mail--tiny, overlapping ceramic disks that would supplement existing armor by providing protection for the groin, shoulders and thighs while still allowing easy movement. Improved composite and integrated ceramic armor are also under development for future army vehicles, he reports.
The real challenge is balancing the sometimes conflicting needs of mobility, firepower and protection. "We would love to have hard ceramic armor completely around the soldier," Fink remarks. "But it would weigh so much and be so inflexible the soldier wouldn't be able to move." That, it should be remembered, was the same problem faced by knights of old.