by Brian Ford
AZON strikes back
The only Allied version of a radio-controlled missile appeared late in the war. This was the American Azon guided missile. It had an octagonal assembly of fins at the tail, allowing its navigational position above the ground — its azimuth — to be remotely controlled (the code name was derived from AZimuth ONly; its official designation was the VB-1, standing for ‘vertical bomb’) and it carried a 1,000lb (450kg) bomb. As in the case of the Fritz-X, a bright flare was fixed to the tail so that its trajectory could be followed by the crew of the delivery aircraft. Others followed; the range extended through to the VB-13 Tarzon which was a sophisticated glide bomb that was being constructed as World War II ended, and went on to be used in the Korean War (1950–53).
The design was originally proposed by two American engineers, Major Henry Rand and Thomas O’Donnell of the United States 458th Bombardment Group, as a means of attacking the Burma railway and was dropped from a B-24 Liberator which was specially modified for the weapon. Few were used during the war. It was the German bombs that proved the principle, and the Allied version came too late to make a difference. The version produced by the Germans established that a radio-controlled glide bomb was a viable weapon, and it has remained a mainstay of present-day warfare.
Simpler rocket weapons were also produced by the Germans. Their R4M missiles were air-to-air weapons that could be fired from pods beneath the wings of Fw-190 and Me-262 aircraft; they were used to break up groups of American bombers in the closing months of the conflict.
The United States began developing sophisticated guided rockets late in the war, and some of their designs were remarkably futuristic. The Consolidated-Vultee Aircraft Corporation designed and built the Lark missile, a surface-to-air device designed to be launched from the decks of ships with solid propellant booster rockets. Its range was up to 40 miles (65km) and it delivered an explosive payload weighing 100lb (45kg). Work on the project began in 1944, but it was not ready for use in World War II. During 1946–50 it was used to refine missile systems and was the first American surface-to-air missile to bring down a test drone in flight.
The Pike and the Fire-Lily
From the start of the war, the Rheinmetall-Borsig Company had carried out design work on the Hecht (Pike) anti-aircraft missile. The Hecht-2700 was conceived as an 8ft (2.5m) long missile weighing 300lb (136kg), fitted with four stabilizing fins, and designed to fly at about 500mph (800km/h). Within two years the project was ended and no missiles of this type were ever constructed.
But the ideas lived on and gave rise to the Feuerlilie (Fire Lily), on which Göring’s German Research Institute for Aviation (Deutsche Forschungsanstalt für Luftfahrt) began work in 1940. The first version attempted was the Feuerlilie (4.4 F), a scaled-down model designed to prove the principle. From this arose the F-25, produced jointly by the German Gliding Research Institute (Deutsche Forschungsanstalt für Segelflug) and the Post Office Research Department (Reichspost-Forschungsamt). Initial problems with the remote-control system were overcome by early 1943 and wind-tunnel tests proceeded according to plan. Further difficulties were experienced in developing the propulsion system, and it was not until 1943 that the first test firing was attempted at Leba, Poland, on the Baltic Sea. Within a year there had been four tests, though none of them was truly satisfactory.
By now, interest was focusing on the successor — the F-55. This was to be a radio-controlled two-stage device with a solid-fuel first stage and a supersonic liquid-fuel second stage. It would be launched somewhat like a plane, with a sloping ramp for take-off. The Ardelt Company in Breslau was given the contract for the production of five test rockets in January 1943, but problems with both the propulsion unit and the remote-control system persisted. The initial order for 25 missiles was reduced to just 11 late in 1944, and early the following year it was agreed to use the control units designed for the successful Hs-293 which were known to be reliable. Decision making continued to be unpredictable, however, and early in 1945 the entire project was scrapped.
The Butterfly
No sooner had Professor Herbert Wagner seen his design for the Henschel Hs-293 successfully realized, than he proposed a new missile concept to the German Air Ministry. Wagner could see a tremendous future for guided missiles, and his new invention was the Hs-117 — the Schmetterling (Butterfly). This would be the next stage after the Hs-293. The idea was that two people would fly what was, in essence, a miniature exploding aircraft. The pilot would fly a Junkers Ju-188, Ju-388 or Dornier Do-217 that would be specially modified to launch the missile, while the other crewman would be solely concerned with steering it towards its target.
Schmetterling was a great advance; rather than being steered as it glided down to its target, this missile could fly wherever the controller desired and would attack an enemy 3 miles (5km) away, even if it was at an altitude far higher than the delivery aircraft. Today’s cruise missiles exploit exactly this kind of technology to the full. It was a brilliant insight, and history has shown how timely Wagner’s ingenious concept was.
Even so, it did not impress the Nazis. Hitler was convinced that he would be victorious, and he felt that his government had invested more than enough in the development of novel guided missiles. Work was scaled down and development soon stopped. The High Command changed its mind in 1943, when the large-scale attacks on Germany began to turn the tide. Hitler now wanted everything he could throw back at the Allies, so the Schmetterling was suddenly revived after all, and with the greatest urgency. During 1944 many of the test firings of prototypes revealed design problems that were methodically rectified, and by the end of the year production was set to start. The order was placed in December, with the missiles scheduled to enter service in March 1945, but by February it was clear that time was running out, and the orders were finally cancelled for good.
Wasserfall Ferngelenkte Flakrakete
This futuristic Wasserfall Ferngelenkte Flakrakete surface-to-air guided missile — in English: the waterfall remote-controlled anti-aircraft rocket — was designed and developed at Peenemünde on the Baltic coast. In some ways it was similar to the V-2 — for example, it was designed to have four tail fins but was also fitted with four near the middle-point of the body to aid control in flight. However, it was one-quarter the size, measuring 26ft (7.9m) tall, with an effective range of 17 miles (27km). And, unlike its famous larger cousin, it could be radio-controlled throughout its flight so it was not a ballistic missile. Another crucial difference was that the V-2, like modern space rockets, was charged with liquid oxygen immediately prior to launch, whereas the Wasserfall was intended to rely on fuels held in store until needed in action, and could then be launched with little notice. In reality, the Wasserfall was intended to stand ready for periods of up to a month and fire on command, so the fuel chosen for the new rocket motor was to be a mixture of vinyl isobutyl ether and SV-Stoff which comprised 94 per cent fuming nitric acid and 6 per cent dinitrogen tetroxide. These were stored in tanks alongside the missile, and were forced in at speed by nitrogen under pressure.
It was the missile’s Rheinland guidance system that was particularly ingenious. This used a simple radar unit to track the target, and a transponder on the missile that was tracked by a direction finder at the launch pad. The operator would see the two spots on the screen and home the missile on the target so that the two spots merged. The rocket exhaust could be diverted from side to side by four graphite vanes placed within the exhaust gas — the same system eventually used for the V-2 — in order to establish it in controllable flight. From then on, as the graphite burned away, four ailerons on the tail fins were used to control the trajectory. Like the earlier examples we have already encountered, the radio control was achieved using the proven 18-channel Kehl/Strassburg system. A later modification was designed, in which the missile would itself home in on a radar beam that was pointed at the target (by the operator) and picked up by transponders on the Wasserfall.
The first proposals had
been to equip the rocket with a 220lb (100kg) warhead but it was soon recognized that only a direct hit — on a vulnerable target — would make this worthwhile; later proposals were for a 660lb (300kg) liquid explosive payload. It was planned that this would create a relatively large sphere of damage within a squadron of bombers, and bring down a number of enemy planes. This was a weapon for which there was a clear demand, and the design work began in 1941. Within a year the details of the final specifications had been agreed and the first flight tests started in March 1943. There were setbacks because of the Allied bombings under Operation Hydra and scarce resources were diverted away from Wasserfall development for a time. Not until February 1945 was there a successful firing that reached a speed of 1,740mph (2,800km/h) in vertical flight. There were some 35 test launches before Peenemünde was finally evacuated as the Allies advanced in February 1945.
The Wasserfall was never deployed; but it represented an advanced kind of remote-control missile and paved the way for later developments. After the war, prototypes were taken back to the United States and test firing took place with a new name — the Wasserfall W-10 was now the American Hermes A-1 Missile. Several modifications to the design were made until the cancellation of the project. By then the A-3 was ready for testing, the project had cost tens of millions of dollars, and it was 1954!
The American flying bomb
The Americans had no super-bomb to match Barnes Wallis’s Tallboy, but developed an idea that they hoped would provide an alternative approach. During 1944, the development of a reliable remote guidance system gave rise to a particularly economical proposal — old airplanes, which had come to the end of their useful lives, would be filled with explosives and remotely flown into enemy targets. This was code named Operation Aphrodite and was developed under conditions of total secrecy by the United States Eighth Air Force. They took old B-17 and PB4Y bombers that were still flying, but no longer repairable, and stripped out all their surplus equipment, loading them to capacity with explosives.
Simple television cameras were fitted so that the view from the cockpit could be followed from an accompanying CQ-17 mother ship. Each aircraft, packed with twice as much high explosive as it had ever carried as a bomber, was to be taken up by a pilot and his co-pilot who would then bail out, leaving the rest of the flight in the control of the mother-ship pilot who steered the old bomber over the target. The Americans saw these as an alternative to the Tallboy bombs manufactured for the Royal Air Force, though they lacked the penetrating power and proved to be less useful. The operation was not considered worthwhile, due to a failure to incorporate the most modern technology. It ran from August to December 1944 but few of the missions were successful.
Operation Anvil was a similar scheme of the United States Navy over the North Sea between Britain and Germany. They converted their old B-24 bombers to become flying bombs, and had the control handled by an accompanying Ventura PV-1 aircraft. The first mission in August 1944 ended in disaster when the plane exploded in mid-air with a tremendous blast. The two crewmen, Navy lieutenants Wilford J. Willy and Joseph P. Kennedy Jr, were blown to pieces. The young Joe Kennedy was being groomed for the American presidency, and his tragic death meant that his younger brother John Fitzgerald Kennedy took his place. The second mission inflicted damage to German establishments in Heligoland, but missed its intended target and so the scheme was discontinued.
At the same time, a batch of surplus B-24D/J Liberator bombers was converted into radio-controlled flying bombs which were to be used against the fortified installations on Pacific islands held by the Japanese. In the same way as Operation Aphrodite, these bombers would be stripped of unnecessary equipment and packed with explosives before being flown to operational altitude by two crew, who would then bail out to safety. Each of these flying weapons contained 25,000lb (11,300kg) of high-explosive Torpex, but the Japanese campaign was never launched.
Enter the buzz-bomb
The idea of a pilotless airplane had first been raised in 1937 when the German Air Ministry issued a contract to the Fieseler Company to supply a radio-controlled flying drone for use as a target. They manufactured prototypes of what became the Fi-157, a low-wing monoplane made of wood and intended to be launched from beneath a bomber. They also manufactured a single Fi-158, a piloted version, intended to try out guidance systems. All of the prototypes were failures, and all crashed out of control. Another approach to the problem had been investigated by Fritz Gosslau at Argus Motoren GmbH and they began to develop a drone at the Argus-Flugmotorenwerke in Berlin-Reinickendorf during the same year. Their design was the As-292 and it was designated Flakzielgerät 43 (Flak-Target Apparatus 43). It first flew as a test version in June 1937 and by May 1939 it was successfully tested with remote-control guidance. Arrangements were then made to install cameras and in October 1939 they were obtaining useful reconnaissance photographs. By the end of 1939 an order for 100 of the planes had been placed, and deliveries began in 1942.
As World War II erupted, one of the first decisions of the German Air Ministry was to investigate the design and development of a pilotless aircraft that could deliver an explosive payload weighing 2,200lb (1,000kg) over a distance of 310 miles (500km). Fritz Gosslau at Argus went into a joint venture with Arado Flugzeugwerke and Lorentz AG to develop the project as a private venture. In April 1940 they announced their provisional design, only to learn within a month that the Air Ministry did not want this weapon after all. The war was going well for Germany, there seemed little opportunity for the weapon to be used in combat operations, and they were not convinced that the little pilotless plane could be safely controlled by radio. But work did not stop, for Gosslau could see the promise of his invention and was determined to have something ready when the tide turned. The engineers at Argus had come up with a design for a pulse jet motor and Gosslau proposed to use two as the propulsion units for his flying machine.
The pulse jet is a simple device. It takes the form of a tubular jet pipe which is closed at the front end by an array of what look like vanes of a Venetian blind. A mist of fuel is injected into the tube and ignited with a spark plug. As it ignites, the vanes slam shut as the fuel explodes and a pulse of hot exhaust is emitted from the rear end of the tube. In flight, this pushes it forward at speed. The lack of air inside the tube, exhausted by the combustion, now causes the burning to cease; the pressure of the air against the vanes blows them open, so a new charge of fresh air rushes in, the new charge of fuel ignites, a further explosion of fuel/air mixture occurs, the vanes snap shut again and so the flight proceeds. The sound is that of a series of muffled fuel explosions repeated 50 times a second and is like a lawnmower engine that needs repair or a small car with a blown gasket. The term ‘buzz-bomb’ was an inevitable coinage for a weapon that produces a sound like that. In Germany it was nicknamed (at Hitler’s instigation) the Maikäfer (Cockchafer or June Bug).
As work proceeded, it was agreed to cut down the number of pulse jet motors from two to one, and since Argus were not specialists in airframe construction the assistance of Robert Lusser, technical director at Heinkel, was brought in. In June 1942 General-Fieldmarshal Erhard Milch gave the authorization of the Ministry for development to proceed as a top priority and in secret. By the end of that year an unpowered version was already being flight-tested. The jet has to fly at a minimum speed of 150mph (240km/h) to maintain operation. Launching was done by flooding the tube with acetylene and setting fire to it from an external battery. The whole craft was then launched from a ramp and — once at speed — it just kept flying. The ramps were powered by hydrogen peroxide (T-Stoff) and potassium permanganate (Z-Stoff) which generated a burst of gas that accelerated the bomb to a launch speed of 360mph (580km/h).
Once aloft, the V-1, as the missile was commonly known, was guided by a simple autopilot invented by the Askania Company in Berlin. An inertial pendulum was attached to a stabilized gyrocompass and the flaps were controlled by compressed air from two large round tanks pressurized to
150atm (15,000kPa) prior to the launch. The same pressure was also used to feed the fuel into the motor. The early V-1 missiles sent towards London were fitted with small radio transmitters to allow their progress to be monitored. A small propeller on the nose of the craft was fixed to an odometer which counted the revolutions — every 30 rotations of the propeller caused the counter to go down by 1. The initial setting was made to match the distance that the pilotless plane was intended to fly; when it had counted down to zero it was above the destination and had reached the planned target. At this point explosive bolts fired within the control mechanism and the V-1 was set to dive into the target. Many people have thought that the odometer shut off the fuel supply, as the V-1 fell silent as it began to fall. That’s not the case — the silence was due to the fact that the sudden drop in the nose prevented the fuel from getting through. The type of V-1 flown later in the war had this fault corrected, so the motor continued to run until the craft hit the ground.
And so the buzz-bomb entered the annals of secret weapons history. The Fieseler Fi-103 V-1 was a flying bomb weighing 4,750lb (2,150kg) and measuring 27ft 3¾in (8.32m) long, 17ft 6in (5.37m) wide from wing tip to wing tip and just 4ft 8in (1.42m) tall. It carried 1,870lb (850kg) of the explosive Amatol-39 and was powered by an Argus As 109–014 pulse jet over a maximum range of 150 miles (250km) and an operating speed of 400mph (640km/h) at an altitude between 2,000 and 3,000ft (600–900m). The buzz-bomb was one of the crudest, cheapest and simplest secret weapons ever developed — and yet it remains one of the best known.
This was Hitler’s first weapon of retaliation, and was also the world’s first successful cruise missile. Known in full to the Germans as the Vergeltungswaffe-1, and nicknamed by the British ‘the doodlebug’, it was designed at Peenemünde by the Luftwaffe during World War II as a terror weapon with which to attack major cities — the principal target being London. The very first V-1 was launched towards London on 13 June 1944 and hit a railway bridge on Grove Road, Mile End, killing eight residents. It was just one week after the Allied landings had begun on the Normandy beaches. Within a month, more than 100 of the V-1 weapons were being dispatched to rain down on London every day. Roughly 30,000 V-1s were manufactured, each taking 350 man-hours and costing 4 per cent as much as a V-2 rocket. Altogether 9,521 doodlebugs landed in Britain before the launch site was occupied by the Allies in October 1944. The remaining weapons available to the Germans were then trained on Antwerp, which received 2,448 attacks until March 1945 when the Allies captured the final launch ramp. The V-1s killed a total of 22,892 people and almost every one of them was a civilian. This was a sustained terror bombing, a cruel and vindictive campaign against a defiant enemy.
