Munroe effect

A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, initiate nuclear weapons, penetrate armor, and "complete" wells in the oil and gas industry.

A typical modern shaped charge, with a metal liner on the charge cavity, can penetrate armor steel to a depth of seven or more times the diameter of the charge (charge diameters, CD), though greater depths of 10 CD and above have been achieved. Contrary to a widespread misconception (possibly resulting from the acronym HEAT) the shaped charge does not depend in any way on heating or melting for its effectiveness; that is, the jet from a shaped charge does not melt its way through armor, as its effect is purely kinetic in nature.

The Munroe or Neumann effect is the focusing of blast energy by a hollow or void cut on a surface of an explosive.

The earliest mention of hollow charges occurred in 1792. Franz Xaver von Baader (1765–1841) was a German mining engineer at that time; in a mining journal, he advocated a conical space at the forward end of a blasting charge to increase the explosive's effect and thereby save powder. The idea was adopted, for a time, in Norway and in the mines of the Harz mountains of Germany, although the only available explosive at the time was gunpowder, which is not a high explosive and hence incapable of producing the shock wave that the shaped-charge effect requires.

The first true hollow charge effect was achieved in 1883, by Max von Foerster (1845–1905), chief of the nitrocellulose factory of Wolff & Co. in Walsrode, Germany.

By 1886, Gustav Bloem of Düsseldorf, Germany had obtained U.S. Patent 342,423 for hemispherical cavity metal detonators to concentrate the effect of the explosion in an axial direction.

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