Currently, insurgent attacks on ground vehicles are the greatest fatality-producing tactic in the terrorists' deadly toolbox. These explosions are sometimes so large that vehicles are lifted and overturned. Some explosions rupture fuel tanks, setting fuel and tires on fire. Petroleum-based materials make very energy-dense fuels, and fires must be extinguished immediately and completely to prevent injury to vehicle occupants. Because of this threat, improved automatic fire-extinguishing systems are needed in ground vehicles.
Fire Suppression History
The first military fire suppression systems (FSSs) were aboard ships and pumped water to douse fires. However, ground military vehicles did not have the capacity to carry water to fight onboard fires, and personnel and vehicles were more often lost than saved. Since hauling FSS water was impractical, other agents were needed.
The first modern FSS was built in 1818. It was a 3-gallon pressurized copper barrel containing potassium carbonate and water. Next, a soda-acid extinguisher was patented in France in 1866; it contained a sodium bicarbonate and water solution mixed with tartaric acid to produce carbon dioxide (CO2). Interestingly, the first foam extinguisher, invented in Russia in about 1905, used water, licorice root, and sodium bicarbonate. Upon mixing, CO2 was produced, with the licorice juice trapping the bubbles to produce foam.
Henri Victor Regnault made a major breakthrough in fire suppression technology in 1839 when he developed the carbon tetrachloride (CCl4) extinguisher, commonly called “carbon tech.” This was the first halon (halon 104), which was produced by chemically combining chloroform with chlorine. (The term “halon” comes from the Army's shortening of halogenated hydrocarbon.) Carbon tech was the first FSS agent that did not leave a residue or, like water, cause additional structural damage to buildings. A CCl4 extinguisher, consisting of a 1-quart capacity metal container and manual pump, was developed in 1911 for automotive use (gasoline fires).
For the next 60 years, CCl4 served as an excellent extinguishing agent that blanketed flames and starved fires of oxygen. However, CCl4 is dangerous to humans. Aspirating or absorbing CCl4 into the body can cause damage to the liver, kidneys, and other organs.
A CO2 extinguisher for electrical fires was developed for Bell Telephone Company in the 1920s, providing a clean extinguishing agent that leaves no residue. During World War II, the Germans invented the more effective chlorobromomethane (halon 1011)—a liquid to be used in aircraft FSSs. Halon 1211, a liquid steaming agent, was used in Europe after World War II and arrived in the United States during the 1970s. Halon 1301, a gaseous flooding agent, was being developed by the U.S. Army and DuPont in the early 1950s as a four-times-heavier-than-air flooding agent to cool and deprive fire of oxygen. It is remarkable that some types of suppression agents are still being used after 100 years.
Today's Military Ground Vehicle FSSs
Current military ground vehicle FSSs extinguish vehicle fires adequately, but the need for faster, safer FSSs is more important than ever. Another requirement for FSSs involves the logistics imperative for commonality among ground vehicle systems. The TACOM Life Cycle Management Command manages hundreds of Army systems, including trucks, combat vehicles, ships, boats, and railroad locomotives.
Each vehicle has its own FSS. Often the same type of vehicle has variants that have different types of FSSs. Each of these FSS types can have a different manufacturer, different extinguishing agent, and different fire-detector sensing equipment. This makes it more difficult to procure, stock, and draft technical manuals to support each system.
The need in the Southwest Asia theater for armor protection in a truck-type vehicle was so great that several manufacturers built platforms using many different FSSs. For example, the new series of mine-resistant ambush-protected (MRAP) vehicles had six manufacturers with eight major variances and several subgroups with different FSSs, constituting the ground vehicle system with the largest number of vehicles and the most different FSS items. Each MRAP original equipment manufacturer installed the FSS that its engineers and FSS manufacturers recommended. As a result, five FSS manufacturers were used.
Each FSS had different fire extinguisher bottles with different agent capacities based on crew compartment volume, different discharge valves with various functions, different detection sensors, different control modules, different wiring harnesses, different switches, and different agents. This created an unreasonable number of Government-stocked FSS items.
Adding to the burden, certain FSSs were randomly discharging, requiring the replacement of discharged bottles and valves before remedies were found and made. Including transportation back to the continental United States (CONUS), the cost to replace one discharged bottle was approximately $2,000. Some Army platforms use up to 10 bottles per vehicle. In all vehicle systems across the theater, thousands of bottles were being used and discarded.
One FSS manufacturer has approximately 12 valve variants used in multiple platforms, each with slightly different functions, and many platform maintainers did not know that other vehicles were using the same valves. Different Government stock numbers were assigned to the same valves for different platforms, causing more confusion and duplicate item stockage. The inability to recharge FSS bottles in theater increased the leadtime to replace bottles, and transportation costs back to the manufacturers were enormous.
With general officer direction, the problems with having bottles discharge randomly and having to send bottles back to the United States for refilling were addressed. Army contracts were awarded to set up FSS refill stations in theater, which began recharging fire extinguisher bottles. FSS manufacturers stopped the unnecessary discharges by sending technical representatives to diagnose errant and erratic discharges and by redesigning sensors.
Refilling FSSs in Theater
Today, numerous contractor-operated FSS refill stations in theater are working hard to ensure that the FSSs are available to protect thousands of vehicle crews. Plans have been made for additional refill stations to serve more theater locations, reduce transportation requirements, and refill bottles faster. Several refilling stations are also being set up in CONUS to better serve the Army. FSS refilling and repair training is being established to reduce the Army's dependence on FSS manufacturers for support.
The Army Product Manager, Sets, Kits, Outfits, and Tools has developed a prototype called the standard automotive tool set field maintenance module 3 (FMM3). The FMM3 is an expeditionary system that can be transported by land, air, or sea to austere environments. It is fully self-contained and is capable of refilling, reclaiming, and maintaining FSS bottles and valves. The FMM3 will fulfill the needs of all FSS agents from CO2 to halon and the different platform systems.
Disposable FSS Bottles
The future of Army vehicle FSSs is progressing to hermetically sealed, disposable bottles with a shelf life of up to10 years that use gas generator propellants (similar to those used in automotive airbags) to discharge the agents. After discharge, the one-shot disposable bottles are demilitarized and sent to a scrap metal recycler. Disposable FSS units can reduce the Army's logistics footprint greatly by eliminating the need for refilling and recharging stations. It also eliminates the need to transport, stock, and store fire suppression agents and to transport bottles back to recharging and refilling stations.
However, reducing the logistics footprint by using only disposable FSS has drawbacks. Each new ground vehicle system being designed, produced, and procured with an automatic fire extinguishing system adds to the logistics burden with new types of FSS bottles, sensors, electrical harnesses, discharge valves, and other components.
The logistics burden of provisioning and stocking a greater variety of items is growing. Commonality among systems is vital to reducing the footprint. Yes, FSS innovations will be incorporated, but a close engineering review of commonality of existing parts must be the second portion of a true reduction of the FSS logistics footprint. Army vehicle automatic FSS designs and choices must be made early in the developmental stage of new vehicles with specific language requirements stating what performance and equipment the Government desires for the best protection of crews and vehicles.