How Strykers Work

The 120-mm cannon of an M1 tank would be a useful weapon for the U.S. Army to have on just about any combat mission. Unfortunately, at a weight of around 60 tons, it takes a great deal of planning and coordination to get an M1 where it needs to go in the world. An M1 is too large to fit on the Air Force's C-130 transport planes. What's more, a vehicle with more firepower and armor usually requires a more complicated support system. This means more specially trained soldiers to operate it, more technicians to maintain it, more parts, and more and larger shells. Thus, the most powerful equipment is often the hardest to move quickly to the battle zone. There are places the mighty M1 can't reach in time to be effective.

The Army's new Stryker project is an attempt to find a workable balance between power and mobility. It's a vehicle system that's built to be as deadly as a tank, as swift as a Humvee and yet mobile enough to be deployed anywhere in the world within 96 hours. In this article, HowStuffWorks explores the thinking behind the Stryker vehicle platform, how it's designed to function in combat and how it fits into the U.S. Army's plans for the future.

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One Stryker, Many Strykers

The Stryker was developed by a consortium of companies led by General Dynamics Land Systems and General Motors Defense. From the ground up, it represents a complete redesign of an earlier General Dynamics project, the LAV or light-armored vehicle. Rather than one vehicle, the Stryker project will produce a family of similar but specialized vehicles, all of which share parts, technologies and a basic structure. This array of vehicles will eventually cover all of the mission objectives the Army faces. The consortium is developing the following different Stryker configurations:

ICV - Infantry Carrier Vehicle
MGS - Mobile Gun System
RV - Reconnaissance Vehicle
MC - Mortar Carrier
CV - Commander's Vehicle
FSV - Fire Support Vehicle
ESV - Engineer Squad Vehicle
MEV - Medical Evacuation Vehicle
ATGM - Anti-tank Guided Missile Vehicle
NBCRV - NBC Reconnaissance Vehicle

Because the Stryker variants are so closely related, all of the vehicles can share repair parts including tires, armor and navigation systems. They require fewer specialized technicians and parts, so they require less space on a transport plane than comparable vehicles. In theory, one type of Stryker could even be transformed into another in a relatively short period of time. This makes the Army far more adaptable and provides military planners with a full range of choices even late in the decision cycle. It ensures that the evolving needs of a particular battle can be met quickly and efficiently.

Tires, Suspension and Powertrain

Let's begin with the elements common to all Stryker configurations. Starting at ground level, the most obvious innovation over earlier light and medium vehicles are the wheels. The Stryker moves on eight wheels, as opposed to the tracks usually found on a tank, heavy truck or armored personnel carrier. A wheeled vehicle is generally much faster than one on tracks, but tracks are capable of traveling on a wider variety of surfaces. So, in keeping with the "best of both worlds" approach of the Stryker project, its tires are built with a new technology that makes them almost as versatile as tracks.

The Eaton/Dana Corporation created a special pressure-control system (CTIS, or Central Tire Inflation System) for the Stryker's eight tires, so that they can be inflated or deflated at will from within the vehicle. This means the Stryker crew can adapt the chassis height and gripping power of the wheels on the fly, giving it much more mobility than a vehicle with fixed tire pressure. A control panel (ECU) in the dashboard is hooked up to sensors and pressurized hoses attached to each tire. This allows the crew to monitor precise tire pressure and make changes with the push of a button. With a top speed of over 60 mph (97 kph), the Stryker is faster than a tank. But thanks to CTIS, like a tank it can travel over both hard and soft surfaces. CTIS also helps to make the Stryker portable. By partially deflating the tires, the Stryker crew can make it more compact for shipment on cargo planes.

The tires are supported by a hydropneumatic, nitrogen-charged, independent suspension system. This works in tandem with the CTIS to create a smooth ride at various heights from the ground.

The Stryker's selectable four-wheel or all-wheel drive is powered by a 350-horsepower,automatic-transmission, Caterpillar turbodiesel engine with a two-speed transfer case. It has six forward speeds and the ability to travel in reverse. Top speed is approximately 65 mph (105 kph), and it can travel 330 miles (531 km) on a 53-gallon tank of diesel fuel. The engine generates 580 lb-ft of torque at 1,400 rpm. It can carry up to 6,500 pounds (2,950 kg) of cargo and generates enough power to tow an additional 10,000 pounds (4,536 kg).

Since this is the same engine found in the Army's medium class vehicles, the Stryker can share repair parts and service personnel with those older units. This is another feature that makes Stryker brigades more efficient and compact.

Defense and Navigation

For armor, the Stryker starts with a 0.5-inch (1.27-cm) thick layer of steel lined in Kevlar. On top of this, the Stryker has a layer of ceramic tile armor, and then some outer areas are also fitted with 3-millimeter plates for reinforcement. Combined, these layers protect the vehicle and its crew from firepower up to a 14.5-mm heavy machine gun throughout the entire vehicle and up to 152-mm high-explosive airbursts from above.

These technologies are designed to ready the Stryker for battles with light-armored trucks and vehicles and small arms fired by foot soldiers, but they are not sufficient shielding from a missile-like rocket-propelled grenade (RPG). As part of the Stryker project, the consortium is designing a special tile that will defend against RPGs, but that technology is still in development. Because of the prevalence of RPGs in the Iraq conflict, each Stryker sent to Iraq was fitted with a thick steel cage, known as slat armor, around its entire surface. Designed something like a catcher's mask, the cage is designed to stop RPGs before they make it to the surface of the Stryker, causing them to detonate before they get close enough to damage the armor plates.

Several other features help keep the Stryker and its crew safe from harm. Its tires are "run-flat." They contain hard-rubber inner tubes that allow the Stryker to keep moving even if the tires burst. The Stryker also has a self-recovery system, which is a heavy-duty winch that can pull it out if it gets stuck in deep trenches or ruts.

Additionally, Kidde Aerospace developed a fire-suppression system for the vehicle, which automatically dispenses fire-extinguishing chemicals if it senses a fire in the troop compartment or in the engine. The system is made up of a central control system hooked up to five to seven tanks that contain the fire-fighting chemicals. Each tank is fitted with a pressure-sensitive switch that sits in front of a bellows with a plunger running through it. The oxygen-burning action of a fire causes a change in air pressure, and that triggers the switch. As the switch moves, it causes the bellows to extend, moving the plunger and releasing the chemicals from the tanks. The system can also be activated or placed in standby mode through the Stryker's control console.

Finally, the Stryker has four M6 smoke grenade launchers, which allow it to virtually disappear to the naked eye behind a curtain of smoke.

Navigation

The Stryker is controlled by two crew members: a driver and a vehicle commander. The driver's seat is just below the hatch. The driver can do all of his or her work inside the sealed vehicle, thanks to three M-17 periscopes and a Driver's Vision Enhancer (DVE) system. Also found on M1A2 Abrams tanks, the DVE is a heat-sensing computer video system that allows the driver to see clearly through darkness, haze and dust. The driver steers with a steering wheel and shifts with a lever very much like that of a car. Technologies like power-assisted steering, anti-lock brakes and the hydropneumatic suspension make the Stryker drive something like a very large and very powerful automobile.

**Inside a Stryker** *Spc. James Buzzard of the 14th Cavalry drives a Stryker vehicle away from the USNS Sisler during offloading operations at the Port of Kuwait.*
Photo courtesy U.S. Army, by Spc. Bill Putnam

The vehicle commander has an array of high-tech systems to help survey the battlefield and plan maneuvers. The commander monitors seven M45 periscopes, a video camera and a thermal imaging system. Perhaps most impressive, adjacent to the commander's seat is a computer terminal hooked up to the FBCB2 (Force XXI Battle Command, Brigade-and-Below) communications system. This is a maximum-security data and communications network that links all of the vehicles on the battlefield and the information they gather in real-time, including reconnaissance drones and eavesdropping systems. Not only does it provide each FBCB2-equipped vehicle with the most current and accurate map of friendly and enemy troop locations, but it also allows Army officers throughout the world to monitor events as if they were on the scene.

Those are the elements common to all vehicles in the Stryker project. Now let's look at what makes each type of Stryker unique.

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Stryker Controversy

Critics of the Stryker, including military analysts, congresspeople and combat veterans, have argued that the project has not met its objectives and may never fulfill the ambitious ideals of the Army Transformation Plan (see the later section Mission: Vehicle for the New Army for details). Discussion has focused on three main problem areas:

Vulnerability - Even with the addition of the slat armor "cage," there is a significant concern that the Stryker is susceptible to RPG attack. As of April 2004, at least one Stryker had fallen victim to an RPG in Iraq. According to reports, of two RPGs fired at this particular Stryker, one got past the slat armor and destroyed the vehicle. (More on slat armor in the next section.) Strykers in the field have also been damaged by bombs and rollover accidents.
Weight and Transportability - The 7,000+ pounds of additional armor added to the Stryker before shipping off to Iraq may have increased its weight and height beyond the standard allowable capacity of C-130 payloads. Even without the added armor, during one phase of testing the Stryker's crew had to temporarily remove several components before it could be loaded on a C-130. After landing, it took as long as 17 minutes to ready the Stryker for its mission.
General Design Flaws - There have been complaints about several systems not working as well as was claimed by the manufacturer. Some combat troops have reported problems with frequent tire blowouts, and the excess weight from the added armor has caused problems with the self-recovery winch. In addition, there are some reports that the slat armor increases the width of the vehicles to such an extent that they can not travel in groups of two, side-by-side, on narrow roads.

Stryker Configurations and Mission

ICV

The Infantry Carrier Vehicle is built both for troop transport and as an offensive force in itself. In addition to the driver and commander, an ICV carries nine infantry soldiers. For weaponry, the ICV features a Konigsberg gun turret, which is operated via remote control from inside the vehicle. The gun turret can be equipped with a .50-caliber heavy machine gun, a 7.62-mm machine gun or a 40-mm Javelin missile launcher.

MGS

**Cannon fire from a Stryker**
Photo courtesy Combined Joint Task Force Seven

The Mobile Gun System delivers true tank-like firepower in a small and maneuverable package. In fact, the MGS is fitted with a 105-mm cannon, the same gun barrel found on the original M1 Abrams tank.

The cannon can fire four different types of ammunition:

HE/HEP (high-explosive) rounds, which penetrate and destroy bunkers and walls
KE (kinetic-energy) ammunition, which destroys armored vehicles
HEAT (high-explosive, anti-tank) ammunition, which attacks vehicles and personnel with its fragmentation capabilities
Anti-personnel canisters, which are designed to attack infantrymen outside of their vehicles

In addition, the MGS has up to two secondary weapons, a 7.62-mm and a .50-caliber machine gun. To match all of this weaponry, the defensive system of the MGS is more robust than that of the ICV. Current plans for MGS armor call for special, reactive armor to go with the current steel structure and ceramic tiles. This Stryker also contains detectors for nuclear, biological and chemical weapons. By definition the heftiest of Stryker variants, the MGS presents the biggest challenge in meeting the weight requirements for rapid deployment by C-130 plane.

The Other Strykers

RV - Reconnaissance Vehicle Carries squads of scouts and surveillance equipment linked in to the FBCB2 system
MC - Mortar Carrier Has a 60-mm and 120-mm mortar capable of firing the full array of mortar ammunition, including heat-, infrared- and precision-guided shells
CV - Commander's Vehicle Contains a large video display system for viewing the FBCB2 tactical maps and a voice system that alerts the commander to danger; for weaponry, has a .50-caliber machine gun and a grenade launcher
FSV - Fire Support Vehicle Is outfitted for advanced command-and-control support including target acquisition, target identification and communications
ESV - Engineer Squad Vehicle Has mine detection and removal systems, a touch screen display for the squad leader, a remote-operated, 50-caliber machine gun and Javelin missiles

A Stryker Engineer Squad Vehicle crew reconfigures their vehicle after being transported aboard an Air Force C-130 Hercules aircraft to Bicycle Lake Army Airfield at the National Training Center, Fort Irwin, CA.
Photo courtesy U.S. Army, by Sgt. 1st Class Gary Ogilvie

MEV - Medical Evacuation Vehicle An ambulance built into a Stryker body; carries either four or six patients and three medics, along with medical equipment and an automatic litter-lifter
ATGM - Anti-tank Guided Missile Vehicle Has a two-tube missile launcher for TOW bunker busters and anti-tank missiles
NBCRV - NBC Reconnaissance Vehicle Contains detection systems for nuclear, chemical and biological weapons, equipment for analyzing field samples for dangerous content and meteorological equipment to monitor and predict weather patterns

As you can see, the array of Strykers is designed to fulfill the needs of virtually every brigade in the Army.

In the next section, we'll examine the specific goals the Stryker project was instituted to address.

Mission: Vehicle for the New Army

To see what makes the Stryker so useful in the field, it is important to understand why it was developed. In the first half of the twentieth century, wars unfolded slowly and deliberately over vast areas of the globe. Transporting heavy equipment over long distances was a livable problem, because both sides were equally limited by how long it took them to move their armies. But in the current political and military climate, crises often erupt without warning and require a swift and powerful response.

**A Stryker Mortar Carrier exits the tail of an Air Force C-130 Hercules aircraft after landing at Bicycle Lake Army Airfield at the National Training Center, Fort Irwin, CA.**
Photo courtesy U.S. Army, by Sgt. 1st Class Gary Ogilvie

Today's conflicts are often too short in duration and small in scale for the older strategies of moving large convoys of equipment slowly along supply lines. Further, today's opponents are often small but determined independent forces rather than large national armies. This puts pressure on the Army's ability to respond to threats all over the world in a timely and powerful fashion. In response to speed-of-deployment problems he faced in the Kosovo conflict in 1999, General Eric Shinseki drafted the "Army Transformational Plan," which called for sweeping changes in the Army's organizational structure to adapt to the new challenges it faced.

General Shinseki's plan ordered the development of a new set of combat brigades to be known as an "interim force." Each of these brigades would be self-sufficient, as powerful as a tank battalion, and able to be deployed by air anywhere in the world within 96 hours. This is no easy task considering that current heavy brigades must be moved by ship and often require weeks to deploy. An interim-force brigade or platoon of brigades would be used in one of two ways:

as a first-responder, establishing and maintaining a presence until the heavier mechanized units arrived
as the main combat element

The Stryker project, a light vehicle designed to maximize speed, firepower, adaptability and interoperability, is the platform that was chosen to enable these new brigades to meet their objectives. If the interim-force brigades are as successful in the field as is hoped, Shinseki's plan then calls for the eventual transformation of the entire Army into an "objective force" where every brigade is capable of meeting similar goals of maximized firepower in a highly portable package.

**Soldiers maintain security for a helicopter landing zone just outside the city of Mosul, Iraq.**
Photo courtesy U.S. Army, by Sgt. Jeremiah Johnson

In order to meet that last requirement, an interim-force brigade's Stryker vehicle must be transportable on a C-130 aircraft, since that is the U.S. Air Force's most common cargo aircraft. The C-130 weight restrictions require a cargo load of no greater than 22 tons, so a Stryker vehicle itself can't weigh more than about 19 tons. Throughout the process of testing and modifying the Stryker for the unique characteristics of live combat missions, meeting this weight requirement has been one of the project's toughest challenges.

If the interim-force brigades and their Strykers meet with success on the battlefield, one day we may see the end of the distinction between light and heavy brigades, and a vast sea of Strykers will head into battle.

For more information on the Stryker project and other military vehicles, check out the links on the next page.