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 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.
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).