The X4, was developed as an Air-to-Air Missile (AAM), although its use of wire guidance paved the way for modern anti-tank missiles, which often used wire guidance for reliability and immunity to countermeasures.
The X4 project started under Dr Max Krammer at Ruhrstahl in 1943. The smooth cruciform of wings were swept back to reduce drag when mounted under a jet fighter. Control was achieved by combined use of tabs on the wings and additional control surfaces on the tail fins. The X4 was powered by a BMW 548 motor which was fed with hypergolic propellants by a complex fuel delivery system, which was designed to prevent fuel starvation during violent manoeuvres.
X4 was launched from the same altitude as the target (from the rear) at more than 1.5km (0.93 miles). The pilot maintained the target and missile alignment after firing, using a small joystick as part of the command link control system. The two control lines were dispersed from bobbins on two of the four wings. It was intended to add acoustic homing and fusing to the 20kg (40lb) of explosive, although most of the missiles used a proximity fuse.
By late 1944, 1,300 missiles had been produced and many hundreds test fired. Successful allied bombing of BMW's Stargard plant destroyed over 1,000 motors intended for the X4, which left 1,000 X4 missiles waiting for motors. This delay was long enough to prevent most of them reaching combat units, as a result only a few were fired in anger. net
The warhead consists of an uncased moulded grain of dinitroglycol-based explosive which depends on high blast effect. The fuze is a combination of acoustic proximity, impact, and self-destroying type. The proximity feature is functioned by aircraft propeller noises and a delay of 1/50-second is provided to enable the missile to approach the target after the acoustic impulse initiates the fuze. The body of the rocket houses the helical aluminum tube fuel tanks and combined two-compartment steel air bottle. The venturi protrudes from the tail portion. The rocket is made to rotate about its axis at the rate of one rotation per second. This permits stabilization in line of flight by a single gyro. The missile is carried on the parent aircraft on a conventional bomb carrier modified for this special purpose
SPECIFICATIONS (not verified)
Length (overall) 200 cm (6 ft., 6 3/4 ins.)Length of warhead 45 cm (1 ft., 5 3/4 ins.)Diameter of warhead (at base) 22 cm (8.675 ins.)Total weight before launching 60 kg. (132.3 lbs.)Weight of warhead 20 kg. (44.1 lbs.)Fuel 4.5 liters (approx.) 98-100% nitric acid 2 liters (approx.) 57% crude m-xylidine 43% triethylamineThrust Initial 270 lbs. to 315 lbs. falling off progressively to 45 to 68 lbs. after 30 seconds.