Reactive armor

A major contribution from chemistry and chemical engineering has been the development of materials with important military applications. Chemists and chemical engineers, working with experts from areas such as electronics, materials science, and physics, have contributed to such developments as new explosives and propellants, reactive armor (a complex material with an explosive layer that can reduce the penetration of an incoming projectile), and stealth materials that reduce the detectability of aircraft by radar. 

Tanks are most important weapon systems for land battles and their performance is decided in terms of fire power, mobility and protection. In order to provide protection to tanks in the battlefield, add-on explosive reactive armor (ERA) has been developed in several countries including India. ERA consists of an explosive layer sandwiched between two plates which are enclosed in metallic containers and fitted on tanks. Such ERAs are reported to provide protection to tanks against HEAT and HESH warheads, hand held anti-tank (A/T) weapons and to some extent against tandem warheads. 

Charges in the shape of a symmetrical sandwich (Fig. 720) (e.g. reactive armor) obey the following relationship ... 

Natural (NU or Unat), depleted (DU), low-enriched (LEU), and high-enriched (HEU) uranium the content of the only natural fissile isotope, U—is an important feature of uranium applications and value. In natural uranium, the content of this isotope is 0.720 atom % or 0.711 wt% (Table 1.2). LEU is defined as U content between 0.720% and just below 20%, while HEU encompasses uranium with U content above 20%. The 20% borderline between LEU and HEU is artificial and was based on the assumption that nuclear weapons with 20% or less U would not be efficient. The waste, or tails, of the isotope enrichment process contains less U than in natural uranium and is defined as depleted uranium (DU). The U-235 content in DU is usually in the range of 0.2%-0.4%. DU is used mainly in armor piecing ammunition, in reactive armor of tanks, in radiation shielding, and is also used as ballast weights in aircraft. In addition, many of the commercially available fine chemicals of uranium compounds are based on the tails of uranium-enrichment facilities and usually labeled as not of natural isotope composition. 

J. N. Armor, Studies in the Reactivity of Ruthenium Ammines, Ph.D. thesis, Standford University, 1970. 

The implications of these deductions seem to lead to the conclusion that such structural factors as chain length, methyl groups, and double bonds influence not only the physical properties but the chemical properties of the hydrocarbon as well. Hydrocarbons are limited in their chemical reactivity. The paraffins are compounds having small affinity. The hydrocarbon molecules are armor-plated with hydrogen. Since structure plays so vital a role in the rate of combustion, there must be a fundamental difference in the relative reactivity of the hydrogen atoms. Experimental evidence that such is the case is accumulating. There are reasons to believe that methods are at hand by which the... 

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