R4M rocket
R4M rockets, on an Me 262's starboard launcher.''
Type	Rocket
Place of origin	Germany
Service history
In service	1944-1945
Used by	Luftwaffe
Wars	World War II
Production history
Designed	1944
Manufacturer	Heber AG, Osterode, Germany
Variants	Air-to-air & Air-to-ground
Specifications
Weight	3.85 kg
Length	812 mm
Width	55 mm
Muzzle velocity	525 m/s
Effective range	600-1,000 m
Maximum range	1,500 m
Filling weight	520 g Hexogen for Air-to-air

The R4M rocket, nicknamed the Hurricane (German: Orkan) due to its distinctive smoke trail when fired, was the first practical anti-aircraft rocket. It was developed by the German Luftwaffe during World War II and used briefly before the end of the war. After the war the R4M served as the pattern for a number of similar systems, used by almost all interceptor aircraft during the 1940s and '50s.

Development

The R4M was developed in order to deal with the increasing weight of anti-bomber weapons being deployed by Luftwaffe fighters. Their designs had started out with the 20 mm MG 151/20 cannons but it was found that it took an average of 20 rounds to shoot down a B-17 Flying Fortress. The 20 mm cannons were then replaced (or supplemented) with the 30 mm MK 108 cannon, which could bring down a bomber with one to three hits. However the MK 108 was much heavier and the larger ammunition made it difficult to carry more than one or two "passes" worth. Worse, the low muzzle velocity of this gun meant they had short range, and in approaching close enough to get hits the fighters placed themselves within the range of the bomber's defensive guns. The more powerful MK 103 cannon had higher muzzle velocity and increased range, at the cost of greatly increased weight and size.

The solution was to replace the gun with a small solid-fuel rocket engine, mounting a warhead similar to that of the cannon shell. Although each "round" was heavier than the corresponding gun-fired shell, the lack of a gun reduced the overall weight considerably. The weight difference was so unbalanced that even a much larger and longer ranged rocket was still lighter than the lower-performance guns it could replace.

The anti-aircraft version of the R4M used a large warhead of 55 mm with 520 g (17.6 ounces) of Hexogen explosive charge, guaranteeing a kill with one hit. Each R4M weighed 3.2 kg and was provided with enough fuel to be fired from 1000 m, outside the range of the bomber's defensive guns. The main body of the rocket consisted of a simple steel tube with flip-out fins on the tail for stabilization. A battery typically consisted of two groups of 12 rockets and when all 24 were fired at once they would fill an area about 15 by 30 m at 1000 m, dense enough that one was almost certain to hit its target. The R4Ms were usually fired in four salvos of six missiles at intervals of 0.07 seconds from a range of 600 m. Two warheads were available for the R4M, the common PB-3 with a 0.4 kg charge for anti-aircraft use and the larger shaped charge, similar in construction to the Panzerschreck, the Panzerblitz II (PB-2), for anti-tank use.

Operations

Only a small number of aircraft were fitted with the R4M, mostly Messerschmitt Me 262s and the ground attack version of the Fw 190s, which mounted them on small wooden racks under the wings.

The weapon had excellent results. French ace Pierre Clostermann notes in his book The Big Show that in March 1945, six R4M-armed Me 262s flying out of the Oberammergau flight test center and led by Luftwaffe General Gordon Gollob claimed to have shot down fourteen B-17s in a mission. In April 1945, R4M-equipped Me 262s claimed to have shot down thirty B-17s for the loss of three aircraft. The Luftwaffe found the R4M missiles to have similar trajectory to the 30 mm MK 108 cannon in flight, therefore the standard Revi 16B was utilized effectively. After the war the R4M served as the pattern for both the US 2.75 in (70 mm) FFAR (Fin-Folding Aerial Rocket) and the larger 5 in (127 mm) Zuni.

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