The SG 500 Jagdfaust was an experimental airborne anti-bomber recoilless rifle designed for use in the Me 163 Komet rocket plane by the German Luftwaffe during World War II. The weapon featured a simple form of automated trigger in which an optical photocell detected the dark silhouette of an Allied bomber replacing bright blue sky and triggered the firing of the armed Jagdfaust guns.
A restored Me 163, shown without the Jagdfaust launchers
The Komet was so fast that pilots found it difficult to fire enough cannon rounds to destroy a bomber in a single pass. The Jagdfaust was developed to address this problem. A 5 cm shell was mounted in a launch tube held in place by a pair of thin pins. Five such tubes were mounted vertically (to fire upward) in each wing root. The design was based on the Schräge Musik, the manually triggered upward-firing air-to-air cannon extensively deployed with the Luftwaffe night fighter squadrons.
The launch tubes were rifled for greater stability of the projectile in flight. The greater resistance of rifling also served to eliminate recoil forces of the weapon affecting the aircraft. When the weapon fired, the force of the launch would break the pins holding the tube in place and the heavy tube was accelerated in the direction opposite to that of the shell. The moving tube corrected for the effect of the launch forces on the airframe. Hence the name, "Fighter plane fist"; like the "Armour fist" or "Panzerfaust," it was a recoilless weapon based on the same Newtonian 'action equals reaction' principle.
The Jagdfaust used a 5 cm "Minengranate" shell, whose thin walls traded fragmentation for additional explosives; when detonated within an aircraft with sheet metal skin, the skin would be blown off to devastating effect.
The entire weapon was designed for economy. Because it was intended for short range use, the shell had an aerodynamically inefficient shape that could be easily forged or stamped. Its tolerances were loose, as its long-range accuracy was not an issue. Instead of a driving band, the shell flared at its base and was machined to engage the rifling. The launch tube was made of soft unalloyed steel since it would not need to keep its rifling over multiple firings. The shell used a simple type of fuse instead of the more complex and expensive AZ 39 Safety Fuse. It was probably shipped pre-assembled and ready to install. The weapon system is credited with one kill, that of an RAF Halifax. Though initial results were promising, the war ended before it could see extensive deployment.
The original article can be found at Jagdfaust and the edit history here.