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STEVEN J. ZALOGA, illustrated by JIM LAURIER
A wartime German propaganda photo purporting to show a V-1 launch. V-1 was only one of a number of names given to the Fieseler Fi-103 cruise missile during the course of its brief combat career. (USAOM-APG)
The V-1 flying bomb was the most widely used guided missile of World War II and the world's first successful cruise missile. In comparison to its wartime stable-mate, the V-2 ballistic missile, the V-1 was significantly simpler, easier to manufacture, and more practical to operate in combat conditions. It was employed for terror attacks against London, Antwerp and other European cities, causing tens of thousands of civilian casualties. But its technical shortcomings and vigorous Allied counter- measures prevented it from fulfilling its mission. (Copies of the V-1 were manufactured by the United States, the Soviet Union, and France, but it was rapidly overtaken by more advanced missile designs in the 1950s.
The idea of converting a small airplane into a pilotless flying bomb is nearly as old as military aviation. In 1915, the Sperry Gyroscope Co. in the United States experimented with "aerial torpedoes" using gyroscopes to guide a small aircraft. Britain followed suit, with weapons such as the Larynx flying bomb launched from HMS Stronghold during trials in 1927. None of these missiles proved practical, but little-known propeller-driven flying bombs remained in development by the US Navy well into World War II.
The most significant German innovation in flying bombs was to use a jet engine. Paul Schmidt was a pioneer of early pulse-jet engines and he was quick to realize that such a simple and inexpensive powerplant would be ideal for a missile. In 1935 he offered a design to the Luftwaffe which he had conceived with Prof. G. Madelung. His flying bomb was ahead of its time, including among its features a novel mid-fuselage air intake. The Luftwaffe, however, rejected the project as "technically dubious and uninteresting from the tactical viewpoint."
V-1 ancestors. (Author)
Entirely separately from these ventures, Dr Fritz Gosslau of the Argus Motor Works in Berlin developed the FZG-43 (Flakzielgerat-43, Anti-aircraft Target Device 43) which was a remote control model airplane for use as a target drone by Luftwaffe anti-aircraft crews. In October 1939 Argus proposed a more ambitious scheme using a larger radio-controlled aircraft dubbed Fernfeuer ("Deep Fire"). It could carry a one-ton bomb-load, and would be controlled by a piloted version of the same aircraft. On delivering its bomb, the Fernfeuer would return to base. This was not a cruise missile like the Schmidt design, but rather an ancestor of today's UCAV (uninhabited combat air vehicle). The Luftwaffe was intrigued by the idea, and Argus worked with other firms including the Lorenz guidance company and the Arado aircraft firm to perfect the idea. However, attempts to win a contract to develop the Fernfeuer in 1940-41 were rebuffed by the Luftwaffe. Although the Luftwaffe was sponsoring a number of projects to develop precision attack missiles, such as the Henschel Hs-293 anti-ship missile, there was no enthusiasm for area bombardment missiles.
In 1941 the efforts of Gosslau and Schmidt began to converge. Argus was primarily an aircraft engine firm, and since 1939 had been working on pulse-jet engine designs independently of Schmidt. Pulse-jets are an earlier, and significantly different, type of engine from the later and more successful turbojet. The first primitive pulse-jet engines had been studied its early as 1908 but did not reach maturity until the 1940s. In a pulse-jet engine, fuel is injected into a combustion chamber where it is mixed with air and then ignited, with the resulting jet exhaust directed back through an exhaust tube. Early studies showed that, under ideal conditions, the combustion cycle could be self-sustaining since secondary shock waves returning to the combustion chamber could be used to ignite subsequent pulses. Nevertheless, there was the need for a practical technique to prevent the jet pulse from also exiting through the air intake at the front of the engine.
In 1940 the Luftwaffe encouraged Schmidt and Argus to cooperate in the hopes of developing a practical design. Schmidt's innovation was a simple but effective shutter system that allowed air to enter the combustion chamber, but which automatically closed when the fuel detonated, forcing the energy back out the exhaust tube. This method was superior to the approaches being studied by Argus, and was incorporated into their next design in late 1940.
The heart of the Argus-Schmidt pulse-jet was this complicated matrix of varies and fuel injectors located at the front of the engine. A mixture of compressed air (1) and fuel (2) was injected into the combustion chamber through nozzles (3) mounted in assemblies (4). The spring steel shutters (6) were mounted to carrier plates (5) and allowed in air to start the detonation process, but prevented the exhaust from exiting the front of the engine. (MHI)
In the meantime Argus had developed an innovative method of injecting atomized fuel into the combustion chamber which permit ted a stable combustion sequence. The resulting Argus-Schmidt engine design was remarkably simple and cheap compared to the rival turbo-jets, and had an excellent power-to-weight ratio. On the other hand, it had several significant drawbacks: it was not fuel efficient and a resonating engine with combustion detonations occurring several dozen times per second caused physical damage to the airframe.
Argus began testing its new pulse-jet engine on automobiles in January 1941, and it first flew on a Gotha 145 biplane on April 30th, 1941. It was promising enough that the Luftwaffe supported further research on more substantial aircraft. Gosslau was intrigued by the idea of using it to power a flying bomb, but Argus lacked an experienced airframe designer. A Fieseler engineer, Robert Lusser, visited Argus on February 27th, 1942, and Gosslau proposed a cooperative effort between Argus and Fieseler on a flying bomb. Gosslau sketched a simple aircraft with a pulse-jet under each wing. Lusser instead sketched an alternative idea with a single pulse jet mounted above the tail. This brief meeting was the genesis of the V-1 flying bomb.