Ruhrstahl X-4 Missile

Ruhrstahl X-4 Missile

The Ruhrstahl X-4 was a German air-to-air missile developed during the Second World War. The Allies’ heavy bombing of Germany during 1943 drove the country to design a new anti-bomber missile. German scientist Dr Max Kramer began work on a missile that could be fired outside the range of guns on Allied bombers. Previously, most German guided missiles used radio signals. However, these could be jammed by the British. To overcome this, Kramer designed a missile that used wires to relay guidance commands to the missile from the cockpit, where the pilot could steer the missile using a joystick.

The X-4 was deliberately designed to be simple enough for unskilled labour to assemble at its manufacturer, Ruhrstahl (Ruhr Steel). The four wings are made of plywood, secured with nuts and bolts. Two of the wings carry small pods containing nearly four miles of wire, which unwound as the missile flew. These can be seen on this example painted black. The other two wings hold simple flares (seen on this example painted red) to help the pilot guide the missile to its target. Its tapered fuselage consists of three sections: a sheet aluminium tail section, a cast aluminium centre, and a turned steel nose that housed the warhead.

The X-4’s 20-kilogram warhead could be detonated in several ways: by the pilot, by impact, or by an acoustic proximity fuse. This acoustic system was tuned to the pitch of American B-17 bombers’ engines, causing the missile to detonate only when it got close to its target. Despite this advanced technology, the X-4 missile was never deployed in combat. The BMW facility that manufactured the X-4’s engines was bombed before they could be fitted into more than a thousand waiting missiles. By this time, it was 1945, the war was almost over, and the project was abandoned. However, the concept paved the way for modern air-to-air rocket weapons.