In 1792, the 26-year-old German Catholic philosopher, theologist, and mining engineer Franz Xaver von Baader came up with a way of saving gunpowder in mines. The idea was to make a conical or mushroom
In 1792, the 26-year-old German Catholic philosopher, theologist, and mining engineer Franz Xaver von Baader came up with a way of saving gunpowder in mines. The idea was to make a conical or mushroom-shaped hollow in the front of the gunpowder charge. His reasoning was not recorded, and it is not clear what effect it had, if any, but it was used in Norway and later in the mines of the Harz Mountains in Germany, but not since.
Gunpowder does not detonate by shock wave the way high explosives do, so the similarity in form of Baader's invention and later shaped charges may be coincidental, since in true shaped charges, the effect is due to focusing the detonation wave, which gunpowder does not have.
The hollow in the gunpowder may well have been to allow the gases to cool a bit before hitting the rock, which, while reducing its effectiveness in moving rock, would have been important in reducing the chance of methane (called fire-damp in those days) explosions.
Things were a little different 91 years later, in 1883. The chief company engineer of the nitrocellulose factory of Wolff & Co., in Walsrode, Germany, was a man named Max Von Förster. Von Förster tested a hypothesis "to give the detonating gases of gun-cotton a certain direction aiming towards the target" through a series of experiments with hollowed-out charges. Aiming at thick wrought-iron plates, he proves his hypothesis, saying, "Estimated on the whole, it appears that the effect of the hollow cartridge of the same size and less weight is superior to the full one of more weight".
Förster had discovered what we now call the unlined cavity principle. It is a shaped charge, but only the explosive gases are propelled forward, and the effect is not nearly as powerful as the lined cavity shaped charge.
In 1885, Gustav Bloom patented a metal detonator cap with a hollow in it, to get a "concentration of the effect of the explosion in an axial direction." This is the first lined cavity shaped charge.
Three years later, in 1888, Professor Charles E. Munroe, a chemist working as a civilian for the U.S. Navy's Naval Torpedo Station, found the same effect in a different way, apparently not having seen Förster's previous work.
In the February 1900, edition of Popular Science Monthly, Munroe describes his experiments:
Among experiments made to demonstrate the resistance of structures to attack by a mob was one upon a safe twenty-nine inches cube, with walls four inches and three quarters thick, made up of plates of iron and steel, which were re-enforced on each edge so as to make it highly resisting, yet when a hollow charge of dynamite nine pounds and a half in weight and untamped was detonated on it a hole three inches in diameter was blown clear through the wall, though a solid cartridge of the same weight and of the same material produced no material effect.
The hollow cartridge was made by tying the sticks of dynamite around a tin can, the open mouth of the latter being placed downward, and I was led to construct such hollow cartridge for use where a penetrating effect is desired by the following observations:
In molding the gun cotton at the torpedo station, as stated above, a vertical hole was formed in each cylinder or block in which to insert the detonator, and in the final press a steel die was laid upon the cake so that an inscription in letters and figures was forced upon it. This inscription was indented in the cylinders and was raised upon the surfaces of the blocks. When the gun cotton was fired untamped, in testing it, the cylinder or block was usually placed with the inscribed face resting on a polished iron plate or iron disk, and after firing, if the gun cotton had detonated it was invariably found that not only was a vortexlike cavity produced below the detonator, but that the inscription on the gun cotton was reproduced on the iron plate, and, what was most singular, when the inscription was indented in the gun cotton it was indented in the iron plate, and when the inscription was raised on the surface