Protection of Army truck requires tradeoffs.

Military truck makers are grappling with how to best satisfy seemingly incompatible goals: building relatively uncomplicated vehicles that can both sustain the rigors of combat and, when needed, effortlessly be plated with thousands of pounds of armor.

Designers and engineers in the United States are learning the hard way that vehicles that originally were not made for crews to survive bomb and grenade attacks cannot simply be shielded with armor, without severely compromising performance and creating new kinds of hazards.

Hanging 1,500-pound armor kits on 7,000 U.S. military trucks operating in Iraq, for example, has led to numerous engine Failures and other malfunctions attributed to the excess weight on vehicles that were not necessarily engineered for those heavy loads, particularly the lighter Humvees. Some truck manufacturers also are concerned that drilling holes in the cab to hang the armor may weaken the chassis.

Fully up-armored Humvees have 3,000 pounds of armor, but come with bigger engines and transmissions. The basic Humvees that are now getting bolt-on armor plates never were intended to carry that much weight over extended periods. The additional weight, further, means that soldiers cannot carry any cargo or extra passengers.

Making trucks "survivable" has to be balanced against practical considerations, such as mobility and operators' needs, said Gem Paul Kern, head of the Army Materiel Command.

"When we do these survivability designs, it's not just a question of encapsulating somebody," Kern said in a recent interview. Vehicle protection must be viewed in the context of the specific environment where troops are fighting, he noted. When Army engineers designed an armor door kit for the Humvee, for example, they had to take into account that soldiers needed to stick their rifles out the window.

For the duration of the Iraqi conflict, soldiers and Marines will make do with current armor technologies, but as new vehicle programs get underway in the years ahead, the Army expects to develop more advanced options. It is a safe assumption that survivability will become a primary consideration in future vehicle designs, said Jeff Carie, program manager at the Army Tank-Automotive Research, Development and Engineering Center. As TARDEC prepares to oversee the new future tactical truck system (FTTS) for the Army, there is a growing consensus that vehicles will need to be designed with the proper axle-loading weight and cab designs that can accommodate armor from the get-go, Carie said.

No adequate substitute yet exists for steel armor, leaving the Army with limited options that don't saddle vehicles with thousands of pounds of extra weight.

The $45 million FTTS program will probe more sophisticated survivability technologies, such as active protection systems, which launch countermeasures against incoming missiles or grenades. But steel-based armor remains the most effective option against small arms, experts said.

"With a new design, you can incorporate different levels of armor protection, instead of having to applique them to a structure that never was designed to accommodate armor kits," Carie told National Defense. "The transmission, engine, suspension can be elegantly upgraded without losing the payload."

FTTS will be an 18-month technology demonstration project. A solicitation to prospective contractors was scheduled for release in July.

The way trucks are being armored now is cumbersome, the equivalent of trying to hang the plumbing after the house is built, said Marc King, U.S. representative for Israel's Plasan Sasa Company, a producer of composite armor for military vehicles.

Factoring crew survivability into the design of a truck is a fairly new phenomenon in the industry, he said. "In the past, it was a feature not considered necessary."

The United Kingdom was among the first countries to specify that armor fitting be a design consideration in its future tracks. The U.K. Ministry of Defense is buying a fleet of 300 tankers, to be built by Oshkosh Truck Corp. Another competition is underway, for up to 2,000 logistics vehicles.

"That doesn't mean the truck will have armor," King said. "But it will be prepared to accept armor if needed ... unlike how we do it today, after the fact."

Plasan Sasa specializes in composite armor, which often is lighter than steel. "We mix and match materials," King said. "We don't just use ballistic steel." A mix of steel or ceramics with Kevlar, for example, can result in lighter armor, depending on the desired protection.

All-steel armor truck cabs will survive huge explosions, but the enormous weight turns them into a logistical nightmare. Germany's Krauss-Maffei Wegman designed a cab for the German Army made entirely of 18 mm armor steel. "It is a work to behold, very well protected, but weighs a gazillion pounds, and it's very expensive," King noted.

In most instances, military customers will trade off certain levels of protection to get the weight down. Cost is another consideration. Adding armor can make the vehicle's price tag soar by up to 30 percent.

Ceramics work better on armored personnel carriers, but are not practical for trucks, simply because this technology is too expensive, King said. Several companies now are making armored cabs that can be interchanged with conventional cabs.

The Army now is testing a steel-Kevlar armor cab for the family of medium tactical vehicles, designed by FMTV manufacturer Stewart & Stevenson. The company plans to make 385 cabs for early deployment to Iraq. One advantage these cabs offer is that they are air-conditioned, noted Regis Luther, director of engineering at Stewart & Stevenson.

Kern said the weight of the cab, at more than 3,200 pounds, is a problem if it cannot be removed when it's not needed. "We are trying to decide if we want to run around with that weight in training," he said. A replaceable cab is a more palatable option, because it can be taken off during training.

For the FTTS program, Luther said, the company is developing an applique armor kit that would hang on top of the armor cab, bolstering the levels of protection by orders of magnitude.

In the midst of the debate of which armor works best, suppliers predict the market for these products will remain on an upswing, at least as long as U.S. and other allied troops remain in dangerous war zones.

Just 18 months ago, said King, "if you had talked seriously to anybody about armoring logistics vehicles, the discussion would have been very brief. Today, the discussions are very protracted."

Military forces not only are armoring Humvee-type vehicles but also medium and heavy trucks across the board. "This is a lesson the government will not forget," said King. "Trucks will have to be designed to be fitted for armor." Armor kits likely will be stockpiled, "so if armour is required, when the truck deploys to the theater, the armor can be added in a couple of hours."

The steady violence in Iraq against truck convoys may, in the short term, silence those who believe that too much armor is counterproductive. Even the Marine Corps, which traditionally favors lighter, more mobile vehicles, is armoring its 7-ton medium trucks, the MTVR, for operations in Iraq. "When we finish armoring the MTVR, the truck cab will be better armored than the Marine Corps light armored vehicles," King said. Unlike the trucks, the LAV was designed for front-line combat. "The level of protection in the MTVR will be higher than the LAV. That's pretty significant."

Plasan Sasa recently delivered new armor kits for the Army's M915 heavy hauler. If the kits pass the required tests, die company will manufacture up to 250.

The amount of armor on current trucks is about as much as they can take, without totally restricting the truck's ability to hold cargo, King said. "I think we've reached the limit."

Active armor and reactive armor may be the only viable alternatives to steel in the foreseeable future, although they only may work on combat vehicles, and not on trucks, according to experts.

Reactive armor can save considerable weight, and is mostly effective against rocket-propelled grenades, not kinetic-energy rounds. Reactive armor tiles generally are attached to the exterior of a tank or armored personnel carrier. Each tile contains an explosive charge that is sandwiched between steel plates. The charge detonates on contact with a shaped charge warhead.

Once a panel blows, however, it leaves that spot vulnerable to further attacks. Some modern warheads, such as the newer TOW antitank missiles, are designed to defeat this type of armor, experts said, by using dual tandem warheads, one detonating a split second after the other. The first detonates die reactive armor and the second attacks the conventional armor left naked underneath.

Israel's Defense Forces have applied reactive armor on their vehicles since 1977, said Yossi Aviram, vice president of business development for Israeli Military Industries.

"We developed it to save weight," he said. Aviram claims that the latest generation of reactive armor, now being installed on M113 personnel carriers, stops RPGs at a 90-degree angle.

The U.S. Army is employing a different type of reactive armor, made by the Rafael Company, on the Bradley infantry fighting vehicle.

A reactive armor package can cost about $150,000.

Aviram does not see reactive armor as a realistic option for logistics vehicles, because truck walls are too thin. Another issue is that trucks generally require small arms protection, in which case, said Aviram, "you are better off with passive armor."

The U.S. Army, meanwhile, continues to pursue research and development work on the most advanced vehicle survivability technology, called active protection. These systems rely on sensors that detect incoming threats and launch munitions to defeat those threats, much like the anti-missile systems used oil aircraft.

Under a project called "full spectrum active protection close-in shield," TARDEC is developing countermeasures against RPGs, anti-tank missiles, and high-explosive antitank ammunition. FCLAS has a sensor and a shim-range grenade launcher, loaded with special fragmentation grenades with delay fuses set to intercept the incoming threat at a range of about 5 meters. The explosive charge is triggered by a side-looking radio-frequency proximity fuze, which senses the incoming projectile as it passes nearby. Tim explosion is intended to kill the passing threat but does not damage the protected vehicle, although many armor officers are not receptive to this technology precisely because they fear it will damage their own vehicles or harm friendly troops. The Army hopes to get a prototype system of FCLAS to be tested on Bradleys, Strykers and Humvees by 2006.

Another active protection technology is being developed by United Defense, possibly for future U.S. Army combat vehicles. Known as the "integrated army active protection system," this technology employs both "soft kill" electronic countermeasures and "hard kill" active protection counter-munitions. The system classifies the inbound threat and assigns a countermeasure to defeat it. The suite includes two types of passive sensors, electronic warfare countermeasures and an active protection system composed of launcher, radar, and a deployed countermeasure. The system is undergoing testing.