The U.S. Army wants to replace the smoke screen the service has been using since World War II.
The U.S. Army Edgewood Chemical Biological Center, which is leading the effort, has pared down its list of candidates to replace the HC Screening Smoke Grenade down to four, according to an Army release.
The grenade the Army chooses must also "have applications in short-range mortars, and long-range artillery shells," according to the Army.
Below is the breakdown the Army offered of the four remaining candidates in its release.
CANDIDATE ONEFirst is a zinc-free composition, HX, similar to the hexachloroethane composition, but one that does not produce a toxic, irritant smoke containing zinc chloride. HC was the smoke of choice for many years, capable of pulling water from the atmosphere and doubling the amount of smoke produced. The HX composition has a similar action except that metals other than zinc produce smoke as dense as the HC, but without high amounts of acidity. "The chemical reaction of the HX composition produces slightly less combustion products and has a higher efficiency, so the result is a similarly dense smoke cloud. This combination makes it the most exciting smoke composition in a long while," Domanico said.CANDIDATE TWO The second composition is hexachloroethane-free. "The advantage of this composition is that none of the ingredients are water soluble, and that nearly eliminates the contamination of water supplies," explained Domanico. By encapsulating chlorine atoms in a plastic matrix, the potential for ground water contamination is nearly eliminated. The chlorine in the matrix is freed by the heat of combustion, allowing the smoke to pull water from the atmosphere and producing a dense smoke cloud. Because the rest of the plastic matrix is carbon, the smoke is filled with fine carbon particles giving a dark gray to black color. This is unusual as the best smoke compositions are white, since white smoke reflects more light than darker smoke, resulting in a more effective smoke cloud.CANDIDATE THREEThe third candidate contains a solid solution of magnesium and aluminum, and produces a large quantity of metal oxides as its main smoke component. Basically, the smoke comes from the burning of the combination of metal powders. This smoke is bright white and easily blends in a bowl with a binder, or in any other suitable mixing system. Using a binder similar to "Super Glue," the composition can be used in grenades, short range mortars and even in long-range artillery, allowing forces to be great distances from their targets. The "Super Glue" binder allows the smoke composition to be pressed into a hard, dense brick that can survive the flight from howitzer to target.CANDIDATE FOURThe Lithium-Plus composition is the fourth smoke candidate. It is based on lithium combustion technology. A chemical reaction uses a lithium salt to produce a superior smoke cloud, pulling large quantities of water from the atmosphere. Lithium salts are efficient, and result in a dense, bright white smoke cloud. The compositions will be tested and evaluated in combat conditions, from cold to hot environments; in forest, desert and urban terrains; and whether or not friendly troops and civilians are in the combat zone.ECBC continues to develop future smoke grenades, mortar cartridges, and artillery shells to offer the best options in future conflicts.