Since the end of the First World War and due to the restrictions imposed by the Treaty of Versailles, Germany encouraged research in the field of rockets, although in a disguised way so as not to annoy the victorious powers. Despite the advances in rocket propulsion systems, this type of device was rejected for military use, but in 1942, when the Luftwaffe began to lose its air superiority, it was decided to start the development of a flying bomb equipped with a explosive charge of 800 kg, under the cover name “Flakzielgerat 76 (FZG-76)” (equipment for flak target 76). In June 1942 the project received the official designation of Fieseler Fi 103, although it was known among the allies as “buzz bomb” or “doodlebug” because of the noise it made in flight. The Germans also nicknamed it “Kirschkern” (cherry stone) and “Maikäfer” (maybug). This weapon mainly consisted of 3 parts, the airframe, the engine and the guidance system. These parts were produced by the German firms Fieseler, Argus and Askania respectively. The fuselage was built of welded sheet steel, with plywood wings, and inside it were the 640 liter fuel tank, the guidance system and the warhead. The guidance system consisted of an autopilot that regulated airspeed and altitude by means of two gyroscopes that controlled yaw and pitch. In addition there was a magnetic compass that controlled the azimuth. Two spherical tanks with compressed air drove the gyroscopes, pressurized the fuel system and serviced the pneumatic servo-motors that operated the rudder and elevator. The warhead of the V-1 consisted of 850 kg of Amatol 52A+ explosive. The bomb had three fuses, one electric, with triggers installed in the nose and belly, another slow-acting mechanical type, which allowed it to explode after penetrating the ground, and another delayed-action fuse. The latter, made the bomb explode two hours after being launched and was created to prevent the capture of the bomb and its subsequent analysis in case it did not explode against the designated target. The V-1 was powered by an Argus 109 pulse jet that developed 279 kg of thrust, and that it was a tube containing a fuel atomization (injection) system and a spark plug. The front was covered by a series of spring-loaded shutters. In flight, the air pushed the shutters, which, when left open, opened the valve that injected fuel into the tube. The air-fuel mixture was ignited by the spark plug and the explosion of the mixture closed the shutters forcing the gases out through the nozzle, producing a thrust jet before the shutters were opened again by the flow of air and the cycle started again. During flight, the motor produced 42 pulses per second. This engine worked effectively only at low altitudes and used low-octane gasoline, making it suitable for powering flying bombs. The stock V-1s had an odometer connected to an anemometer that determined when the target had been reached. Before the launch, the counter was set to a certain value that went down to 0 as it approached the target. While in flight, the airflow moved a small propeller, which every 30 turns decreased the counter by one point. At 60 km from takeoff, the fuse was armed and when the counter reached zero, two explosive bolts detonated, releasing two small deflectors in the elevator, at the same time that a guillotine severed the rudder servo hoses causing the V-1 went into a steep dive. It was known when it was going to impact because the pulse jet stopped and the typical buzzing noise it caused during the flight ceased. The guidance system did not allow to attack targets precisely, but rather to attack a certain area. When they entered service the V-1s fell in a circle of about 30 km in diameter from the intended target, but at the end of the War the guidance system was improved allowing hits in a diameter of about 10 km. This improvement allowed the latest V-1 to be as accurate as the V-2 ballistic missiles. The V-1s launched against London were aimed at Tower Bridge, somehow ensuring that they landed in the center of the city. The V-1, like all bombs, had to have a launch system, and two different systems were prepared for it. One consisted of airdropping by means of a bomber modified for this purpose. The bomber chosen for this task was the Heinkel He-111 H-22, specially modified, which could carry a single V-1 on each combat sortie. The other system, which would be the most common, consisted of launching from the ground by means of a steam catapult. This system was in charge of the German company Walter-Werke.
All He-111 H-22 bombers were assigned to “III/Kampfgeschwader 3” (3rd Squadron/3rd Bomber Wing) based in the Netherlands. They developed a so-called “lo-hi-lo” attack tactic consisting of flying extremely low to the launch point, then initiating a slight ascent to 450 meters in altitude to fire the V-1 bombs, and descending again to return to base. These attack missions began on June 9, 1944, in response to D-Day, and ceased in January 1945 after launching some 1,175 V-1s. From June to September 1944 the III/KG3 squadron launched 300 V-1s against London, 20 against Bristol, 90 against Portsmouth and Southampton and 23 against Paris losing only two bombers during this campaign, a complete success. The ground launch system was made up of the Walter WR 2.3 steam catapult and a gas generator that produced high-pressure steam that moved a piston on which the V-1 was attached. Steam was produced by mixing hydrogen peroxide (T-Stoff) and sodium permanganate (Z-Stoff). Once in the launch position, a hose with compressed air was connected to the engine intake and an electrical connection to the autopilot and the spark plug, leaving everything ready for firing. This was done from a console with 3 selectors. the first fired the pulsejet, the second accelerated the same, and the third fired the V-1. In 7 seconds the acceleration of the engine was ideal and after firing, in less than a second the bomb was accelerated to 320 km/h. The Walter WR 2.3 catapult consisted of a 49 meter long ramp made up of 8 sections of 6 meters each and a muzzle brake. There were three types of V-1 launch bases named “Wasserwerk”, “Stellungsystem” and the more simplified “Einsatz Stellungen”. 4 huge Wasserwerk bases were built in Desvres, St. Pol, Valognes, and Cherbourg (France). Around 50 launchers of the Stellungsystem type were distributed in three bases in the Pas-de-Calais, Rouen and Caen area and another 80 launchers, (plus 16 support), of the Einsatz Stellungen type were installed from Calais to Normandy. In early December 1942, the first unpowered test flight was made, launching an FZG-76 from an aircraft. On December 24, a Fw-200 Condor aircraft launched the first prototype that flew under its own power over Peenemünde. Some bomber-launched V-1s are reported to have been tested in 1944 in Finland, where witnessing Finnish soldiers called them “flying torpedoes”. Initially, it was calculated that the bombs would have a range of about 480 km and that they would reach a speed of between 720-800 km/h, but finally the figures were established at a range of about 240 km and a speed between 500-640 km/h. The operational flight altitude was calculated at about 2,750 meters although various mechanical problems usually prevented reaching this ceiling. However, the improved V-1s launched over Belgium in October 1944 flew at 900 meters altitude and were much more difficult to shoot down. The order to start production was given in September 1943 to start the attacks on London in February 1944, when 1,400 V-1s were to have been prepared. Due to Allied air raids on Peenemünde and various workshops, this goal was not achieved and by April 1944 there were only about 1,000 completed. Production was centralized in a gigantic underground plant at Nordhausen, and by June 1944 some 12,000 bombs had been completed. In August 1943 the Flak Regiment 155 (W) was created to operate the V-1. The unit was made up of 3,500 men divided into 4 battalions. Each battalion consisted of 2 supply and service sections and 4 firing teams. Each firing team could serve 4 launch ramps, so in theory this battalion could simultaneously launch up to 64 V-1s. The first operational launch was carried out on June 9, 1944 and was carried out from Heinkel He-111 H-22 bombers. On the other hand, the first launches from the ground were carried out during the afternoon of June 12, 1944, although it was not until the night of the 15th to the 16th that the first “rain of flying bombs” was dropped against Great Britain. That night a total of 244 were launched against London and 53 against Portsmouth and Southampton. Of all launched, 45 crashed shortly after launch due to mechanical failure, 25 were destroyed by anti-aircraft artillery, and 7 were shot down by Allied fighters. Despite the lack of precision of the V-1, being a weapon created to instill fear, this objective was fully achieved. The 850kg warhead was lethal up to 15m from impact, destroying surrounding buildings up to 70m and causing structural damage up to 180m. The low manufacturing cost of only 5,090 Reichmarks made them ideal for release in large numbers. Some 30,000 V-1s were built, of which 10,000 were launched against Great Britain and more than 12,000 against Belgium. The cities that received the most punishment were: Antwerp (8,896), Liège (3,141) and London (2,419). In London, more than 6,000 people died and nearly 18,000 were injured. The V-1s were not unscathed by the allied defenses, which from the beginning managed to destroy a good number of them. This was no easy task, as the V-1s flew too high for the light anti-aircraft guns but too low for the heavy guns to follow. Many were also shot down by fighters, although due to the high speed of the V-1s, only aircraft such as the Tempest, Meteor or Mustang managed to reach them. The antiaircraft batteries were distributed creating defensive belts that over time came to shoot down up to 80% of the incoming V-1. Initially it took about 2,500 rounds to get a shot down, but by the end of the War the ratio dropped to about 100 rounds per shot down. The V-1 emplacements became preferred targets for the Allied Air Force, but it must be said that these emplacements were very difficult to locate and were not usually destroyed in bombing raids. Only the Allied land advance in France managed to put these places out of action, as they were abandoned by the German troops. Due to the loss of these bases, at the end of 1944 a new variant of the V-1 called “Fi-103E-1” or “F-1” was developed. This new variant had a longer range, about 400 km, but a smaller warhead. However, this greater range made it possible to attack London from new locations in the Netherlands. In March 1945 some 275 were launched against London, but only 13 reached the city. Later it was decided to launch them against advanced RAF airfields with the intention of reducing the almost total Allied air dominance. Another German measure to counter Allied defenses was to return to air-dropping V-1s. For this, the III/KG3 squadron was deployed further to the rear and was joined by another new squadron, the KG53, totaling more than 100 bombers. However, in late 1944 a Wellington bomber was modified to carry radar which was capable of directing night fighters of the RAF’s Fighter Interception Unit against German aircraft. The effectiveness of this “AWACS” is evident in the fact that in January 1945 the German squadrons had suffered 77 kills against the launch of 1,776 V-1 of which only 388 reached Britain, and only 66 of them hit London. After the German surrender, some allied countries such as the United States, USSR and France captured some V-1s that they submitted to study and experimentation. The United States developed 2 missiles, the JB-2 for the USAAF and the KGW-1/LTV-N-2 Loon for the Navy (on the image). Although they did get into production, Japan’s surrender eliminated this need and the KGW-1 served to develop later American cruise missiles. The USSR developed a missile designated “Izdeliye 10” which was scrapped in the early 1950’s for its inaccurate guidance system. France was the one who took the most advantage of the captured V-1, and after the use of reverse-engineering, developed an air or ground launch target drone called Arsaero CT-10. Some of these drones were exported to Italy, Sweden and the UK.
