Conventional armor may be subjected to a variety of projectiles designed to defeat the armor by either penetrating the armor with a solid or jet-like object or by inducing shock waves in the armor that are reflected in a manner to cause spalling of the armor such that an opening is formed and the penetrator (usually stuck to a portion of the armor) passes through the armor, or an inner layer of the armor spalls and is projected at high velocity without physical penetration of the armor.
Some anti-armor weapons are propelled to the outer surface of the armor where a shaped charge is exploded to form a generally linear “jet” of metal that will penetrate solid armor. Such weapons are often called Hollow Charge (“HC”) weapons. A rocket propelled grenade (“RPG”) is such a weapon. An RPG 7 is a Russian origin weapon that produces a penetrating metal jet, the tip of which hits the target at about 8000 m/s. When encountering jets at such velocities, solid metal armors behave more like liquids than solids. Irrespective of their strength, they are displaced radially and the jet penetrates the armor.
Various protection systems are effective at defeating HC jets. Amongst different systems, the best known are reactive armors that use explosives in the protection layers that detonate on being hit to break up most of the HC jet before it penetrates the target. Such systems are often augmented by what is termed “slat armor,” a plurality of metal slats disposed outside the body of the vehicle to prevent the firing circuit of an RPG from functioning.
A second type of anti-armor weapon uses a linear, heavy metal penetrator projected at a high velocity to penetrate the armor. This type of weapon is referred to as EFP (explosive formed projectile) or SFF (self forming fragment), sometimes referred to as a “pie charge” or a “plate charge.
In some of these weapons the warhead behaves as a hybrid of the HC and the EFP and produces a series of metal penetrators projected in line towards the target. Such a weapon will be referred to herein as a Hybrid warhead. Hybrid warheads behave according to how much “jetting” or HC effect the hybrid warhead has, and up to how much of a single, large penetrator-like EFP it produces.
Another type of anti-armor weapon propels a relatively large, heavy, generally ball-shaped solid projectile (or a series of multiple projectiles) at high velocity. When the ball-shaped metal projectile(s) hits the armor, the impact induces shock waves that reflect in a manner such that a plug-like portion of the armor is sheared from the surrounding material and is projected along the path of the metal projectile(s), with the metal projectile(s) attached thereto. Such an occurrence can, obviously, have very significant detrimental effects on the systems and personnel within a vehicle having its armor defeated in such a manner.
While the HC type weapons involve design features and materials that dictate they be manufactured by an entity having technical expertise, the latter type of weapons (EFP and Hybrid) can be constructed from materials readily available in a combat area. For that reason, and the fact that such weapons are effective, these weapons have proven troublesome to vehicles using conventional armor.
The penetration performance for the three mentioned types of warheads is normally described as the ability to penetrate a solid amount of RHA (Rolled Homogeneous Armor) steel armor. Performances typical for the weapon types are: HC warheads may penetrate 1 to 3 ft thickness of RHA; EFP warheads may penetrate 1 to 6 inches of RHA; and Hybrids warheads may penetrate 2 to 12 inches thick RHA. These estimates are based on the warheads weighing less than 15 lbs and being fired at their best respective optimum stand off distances. The diameter of the holes made through the first inch of RHA would be: HC up to an inch diameter hole; EFP up to a 9 inch diameter hole; and Hybrids somewhere in between. The best respective optimum stand off distances for the different charges are: an HC charge is good under 3 feet, but at 10 ft or more it is very poor; for an EFP charge a stand off distance up to 30 feet produces almost the same (good) penetration and will only fall off significantly at very large distances such as 50 yards; and for Hybrid charges penetration is good at standoff distances up to 10 ft, but after 20 feet penetration falls off significantly. The way these charges are used is determined by these standoff distances and the manner in which their effectiveness is optimized (e.g., the angles of the trajectory of the penetrator to the armor). These factors affect the design of the protection armor.
While any anti-armor projectile can be defeated by armor of sufficient strength and thickness, extra armor thickness is heavy and expensive, adds weight to the armored vehicle using it, which, in turn, places greater strain on the vehicle engine and drive train, and thus has a low “mass efficiency.”
Armor solutions that offer a weight advantage against these types of weapons can be measured in how much weight of RHA it saves when compared with the RHA needed to stop a particular weapon penetrating. This advantage can be calculated as a protection ratio, the ratio being equal to the weight of RHA required to stop the weapon penetrating, divided by the weight of the proposed armor system that will stop the same weapon. Such weights are calculated per unit frontal area presented in the direction of the anticipated trajectory of the weapon.
Thus, there exists a need for an armor that can defeat the high energy projectiles (i.e., projectiles having velocities of greater than about 2500 m/s) from anti-armor devices without requiring excess thicknesses of armor, and thus have a high mass efficiency. Such armor may be made of materials that can be readily fabricated and incorporated into a vehicle design at a reasonable cost, and may be added to existing vehicles.
The present disclosure is directed to overcoming shortcomings and/or other deficiencies in existing technology.
USPTO Backgrounds
USPTO Backgrounds