Ruhrstahl X - 4
By Peter Alway
It was one of those futuristic German secret weapons of WW II: the Ruhrstahl X-4.
The X-4 was an experimental wire-guided air-to-air missile. Its liquid fueled engine burned Tonka 250 (a mix of xylidine and triethylamine for you chemists out there) with nitric acid.
The propellants were stored in two long helical tanks on the theory that maneuvers in flight wouldn't slosh the propellants away from the tank outlets.
Two wing tip pods held spools of wire-each over 3 miles long-to receive commands from the pilot of the German plane that launched the missile.
Flares on the other two wing tips insured that the pilot could see what he was guiding.
Metal tabs on the wooden wings induced a stabilizing roll in the missile. An internal gyroscope allowed the missile to sort out pitch and roll commands and send them to the appropriate flaps on the tiny tail fins.
The rumble of an American B-17 bomber's engines triggered a fuse that set off the X-4's explosive warhead. A well-placed allied bombing raid destroyed the factory producing the engines, ending the project.
Several individual missiles survived, and Jim Fackert and I measured and photographed the one that made its way to the US Air Force Museum.
Another member, Goeff Semrau took some digital photos.