Historical Development of Linear Shaped Charge

The use of linear explosive products for launch vehicle, strategic missile, tactical missile, and aircraft applications is very common in today’s aerospace industry. Ensign-Bickford pioneered the development of low core load linear explosive products more than 50 years ago including the development of linear shaped charge products in 1957. This paper highlights some of the historical challenges in developing linear shaped charge and mild detonating fuse and provides insight into the early development work that was done. I. History s with all technology, the development of the shaped charge is no different. An idea was brought forth by a forward thinking individual or individuals, the idea was tested and explored, theories were postulated for why the technology works, and applications for the technology were investigated. As more work on the technology was performed, interest grew, pulling in more and more theories, ideas, tests and applications. The idea of a shaped charge was first discovered by Charles E. Munroe of the Naval Torpedo Station, New Port Rhode Island in 1888. Munroe detonated blocks of explosive in contact with steel plates. The explosive charge had the initials U.S.N. (United States Navy) inscribed on the charge opposite the point of initiation. The initials were reproduced in the steel plate. Munroe further observed that when a cavity is formed in a block of explosive, opposite the point of initiation, the penetration of the crater produced in the target increased. In other words, a deeper cavity could be formed in a steel block using a smaller mass of explosive. This effect has been termed the Munroe Effect and is the focusing of the detonation products due to the chevron shape created in a charge. The idea of a hollow charge was born. Munroe furthered this concept by developing one of the first lined shaped charges in 1894. He created a device that consisted of a tin can with sticks of dynamite tied around and on top of it, with the open end of the can pointing downward. The device punched a hole in the top of a safe. Many theories have been put forth to describe the jet formation and cutting potential obtained from shaped charges. Early theories claimed that the penetrating jet was due to either a focusing of the detonation gases, the formation of multiple interacting shock waves, the spallation of the liner material, or some combination of these effects, including the theory that jets of gas break through the metallic liner and carry fragments resulting from the rupture and erosion of the liner. An interaction of these jets then causes a strong forward wave that imparts a high velocity to the liner particles. Then in 1943, Birchoff (1943, 1947) put forth a preliminary theory to describe the physics that occurs during the jet formation process. He claimed that upon initiation of the shaped charge, a detonation wave begins to propagate through the explosive core at the detonation velocity of the explosive. When the detonation wave reaches the liner, the liner is subjected to the intense pressure of the front and begins to collapse along its axis of symmetry. This extruded material is the jet. The intense pressure far exceeds the yield strength of the liner material allowing the material to be treated as an in viscid, incompressible fluid. . This basic theory holds true