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 which could be fired outside the range of the bombers' guns. Previously, most German guided missiles used radio signals. However, these could be jammed by the British. To overcome this, Kramer designed a missile which 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 purposefully simple so that it could be assembled by unskilled labour at manufactures Ruhrstahl (Ruhr Steel). The four wings are made of plywood, secured with nuts and bolts. Two wings carry small pods which contain nearly four miles of wire which unwinds when the missile is fired. 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 which housed the warhead.

The X-4’s 20-kilogram warhead could be detonated several ways; by the pilot, by impact or by an acoustic proximity fuse. This acoustical system was tuned to the pitch of the engine of a B-17 bomber and would cause the missile to detonate when it reached proximity to the bomber. Despite this advanced technology, the X-4 missile was never deployed in combat. The BMW facility which manufactured the X-4 engines was bombed before they could be fitted into over a thousand waiting missiles. By this time, it was 1945, the war was almost over and the project never recovered. However, the concept provided the foundation for modern air-to-air weapons.

The X-4 we have on display is on loan from the Royal Air Force Museum Reserve Collection. It was restored by the National Space Centre.