 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Ruhrstahl X-4" – news ·newspapers ·books ·scholar ·JSTOR(October 2009) (Learn how and when to remove this message) |
| Ruhrstahl X-4 | |
|---|---|
 Surviving example at theNMUSAF | |
| Type | Air-to-air missile |
| Place of origin | Nazi Germany |
| Service history | |
| In service | Not operational |
| Wars | World War II |
| Production history | |
| Manufacturer | Ruhrstahl AG |
| Developed into | Ruhrstahl X-7 |
TheRuhrstahl Ru 344 X-4 orRuhrstahl-Kramer RK 344[1] was awire-guidedair-to-air missile designed by Germany duringWorld War II. The X-4 did not see operational service and thus was not proven in combat but inspired considerable post-war work around the world,[citation needed] and was the basis for the development of several ground-launchedanti-tank missiles.[citation needed]
During 1943, theRAF'sBomber Command and the US Air Force mounted a series of heavy raids against Germany. Despite heavy bomber losses, these promptedLuftwaffe research into considerably more powerful anti-bomber weaponry in order to reduce the cost in lostfighter aircraft and aircrew. A massive development effort resulted in a number of heavy-calibreautocannon designs,air-to-air rockets,SAMs, and the X-4.
Work on the X-4 began in June 1943, byMax Kramer atRuhrstahl AG [de]. The idea was to build a missile with enough range to allow it to be fired from outside the range of the bombers' guns (a concept now known asstand-off weaponry). The bombers' defensive guns had a maximum effective range of about 1,000 m (3,300 ft). The missile was to be guided with enough accuracy to guarantee a "kill". The X-4 met these specifications and more. ItsBMW109-448 rocket motor accelerated the missile to over 1,150 km/h (710 mph) and kept the X-4 at this speed during its "cruise", between 1.5 and 4 km (0.9 and 2.5 mi).
The rocket burned ahypergolic mixture ofS-Stoff (nitric acid with 5%iron(III) chloride) andR-Stoff (an organic amine-mixture of 50%dimethylaminobenzene and 50%triethylamine calledTonka 250) as propellant, delivering 140 kg (310 lb) thrust initially, declining to 30 kg (66 lb) over the 17-second burn.[2] As there was no room for afuel pump, the fuel components were forced into the motor by pistons inside long tubes, the tubes being coiled (similar to acoil spring) to fit inside the airframe. S-Stoff was socorrosive, it dissolved allbase metals and was extremely difficult and dangerous to handle. The Germans planned to replace the motor with asolid fuel design as soon as possible.
The missile wasspin-stabilized at about 60rpm or one rotation a second,[3] so any asymmetrical thrust from the engine or inaccuracies in the control surfaces would be evened out. Signals to operate control surfaces on the tail were sent via two wires (a method chosen to avoid radio jamming),[4] which unwound frombobbins housed within long, bullet-shaped fairings, themselves mounted either on the roots of an opposing pair of the larger mid-body fins (there were four, swept 45°),[5] or on one pair of those same fins' opposing tips; these contained a total of about 5.5 km (3.4 mi; 3.0 nmi) of wire.[6] The wires were controlled by ajoystick in the cockpit.[7] Agyroscope kept track of "up" so control inputs from the pilot's joystick in the launch aircraft could be translated intoyaw andpitch as the missile spun. Flares attached to two of the midsection wings were used to keep the missile visible through the smoke of its motor.
The warhead consisted of a 20 kg (44 lb)fragmentation device that had alethal radius of about 8 m (26 ft). It was thought that the guidance system would allow the pilot to get the missile into this range in terms of pitch and yaw. But with the ranges the missile could operate at, it would be almost impossible to judge range to the target bomber anywhere near this accuracy. For this reason the missile mounted aproximity fuze known as aKranich (Crane), using an acoustical system tuned to the 200 Hz sound ofthe B-17's engines in cruise mode,[8] activated by theDoppler shift as the missile approached.[9] The trigger range was seven metres (23 ft).[10]
The first flight test occurred on August 11, 1944, using aFocke-Wulf Fw 190 for the launch platform.[11] Subsequent tests used theJunkers Ju 88 andMesserschmitt Me 262, although they were not launched from the latter. The X-4 had originally been intended for use by single-seat fighters (including the Me 262 and possibly theDornier Do 335),[12] but the problems in guiding both the missile and the aircraft at the same time proved unworkable. Instead, the X-4 was re-directed to multi-seat aircraft like the Ju 88, while the unguidedR4M rocket was to be used in single-seaters.
The X-4 was designed to be easily assembled byunskilled labour[example needed] andairframe production began in early 1945 incorporating low-cost (non-strategic) materials, such as wood for fins.[13] Production was hampered by Allied bombing of the BMW rocket engine factory atStargard, though as many as 1,000 X-4s may have been completed,[14] the missile was never officially delivered to theLuftwaffe.[15] Thefighter-interceptor designed to use this missile as its primary weapon was theFocke-Wulf Ta 183Huckebein, which never got out of the project stage.
After the war, French engineers tried to develop a domestic version of the X-4, theNord SS.10. 200 units were manufactured between 1947 and 1950. However, the program was disbanded due to the dangerous pre-flight refueling involved (the hypergolic nitric acid and Tonka combination was highly explosive).
