Hitler's Terror Weapons

VII U-boat fitted with a hangar on the foredeck could carry four V-1s and launch them with impunity within a few minutes at night or in fog. They need approach no closer than 300 kilometres from the coast.
It was not quite so simple as it seemed, however. By the end of 1944 all Type XIV boats had been sunk and the US offshore anti-submarine defences were such that the Kriegsmarine considered only the new Type XXI Elektro-boote capable of carrying out the operation with a prospect of surviving it. Another material drawback was the inaccuracy of the V-1. It was not remote-controlled at that stage and this factor, compounded with the pitch and roll of the boat at launch while firing on a compass bearing at a city 300 kilometres away, made the planners wonder if the target could ever be hit.
In order to overcome these problems a remote control system was tried, a version of the ZSG Radieschen, a passive radar which was fitted to the BV 246 glider bomb and homed in on enemy radar and Loran transmitters. This 15 kg target-seeker was found successful. A similar idea was in effect for the A9/10 rocket. The remaining technical problems to be surmounted were the relatively poor quality transmitters available and the need to have somebody put the set in place and turn it on at the right time at the target end. This meant that a number of agents would have to be landed in the United States for the task. A special version of the sea-launched V-1 was ready for use in November 194414, probably the Fi-103E, but the OKL development contract awarded to the Deutsche Forschungsanstalt für Segelflug for the V-1 Radieschen, which resulted in the Ewald II homing device and the Sauerkirsch II radio remote control system, did not bear fruit until April 1945, by which time hopes for the V-1 campaign were dead.
The V-2
The V-2 was the A-4 giant rocket 14 metres in length, 1.6 metres at the widest point of the fuselage and 3.5 metres across the tail assembly. Takeoff weight was 12 tonnes including a 1-tonne warhead in the nose. The rocket was transported aboard a chassis known as a Meillerwagen which was towed by a road or rail locomotive. At the launch point it was raised upright on the detachable starting platform for firing. The fuel was a grain alcohol/liquid oxygen mixture which burned for about a minute before the rocket fell to earth in a ballistic trajectory. Maximum altitude was 80 kilometres and the range was up to 305 kilometres. During powered flight the projectile was remote-controlled from the ground or regulated by an onboard gyro-compass.
The impact of an A-4 was equivalent to fifty 100-ton steam locomotives hitting the ground simultaneously at 70 mph. Even without its warhead the rocket would excavate a crater thirty feet deep and 75 feet in diameter. The London correspondent of a Swedish national daily reported: “I have personally seen great craters made by the V-2. In urban areas a single projectile can ruin 600 houses. It is not the explosion or blast that does the damage, but the tremendous earthquake effect.”
Accuracy was poor, however, and only 50% fell within 10 kilometres of the aiming point.
The V-2 offensive against London opened from The Hague on 8 September 1944, the first missile falling in Chiswick; the last fell on 27 March 1945. The despatch rate began at four per day and climbed to twenty-five units per day. Of 1269 launches against England, 1115 rockets (87%) arrived. The death toll from these was 2724 persons. 1739 A-4 missiles were fired at cities in France, Belgium and Holland, plus ten at Remagen, of which 1265 (73%) arrived, causing 7000 fatalities.
271 (0.8%) rockets of the total fired were designated failures.15
Whereas General Dwight Eisenhower was of the opinion in his memoirs that if the A-4 had been operational six months earlier it would have made the invasion “extremely difficult if not impossible”, Armaments Minister Speer took the view that “the enormous scientific and technical effort, together with the bottleneck caused in raw materials and fuels, prevented a large number of jet fighters being built instead”.
In the autumn of 1943 Otto Lafferenz, a director of the Deutsche Arbeitsfront, suggested to Peenemünde Weapons Testing Centre the building of a number of submersible containers, each holding a V-2 rocket. A U-boat would tow three of these 500-tonne barges, each 37 metres in length and 5.5 metres in diameter, underwater to the coast of the United States and, when within 300 kilometres of the target, flood the ballast tanks of the barge to bring it to an upright position projecting about 5 metres above the surface. This would allow the rocket to be fired from a gyroscopically stabilized platform.16
Trials were carried out with U-1063 and apparently similar experiments were conducted later at Lake Toplitz in the Austrian Alps when manned midget submarines practised firing rockets which resembled small-scale V-2s.17 A Kriegsmarine naval experimental station (CPVA) was located on the shore. The Lafferenz project was codenamed Teststand XII and Projekt Schwimmweste, and orders for the barges were placed with Stettiner Vulkanwerft and Schichau Werft Elbing in early December 1944.
It had been found in October 194318 that a U-boat towing a submerged barge had to maintain at least 4.1 knots through the water at periscope depth, for at 3.9 knots the barge lost the dynamic force necessary to hold it under. Various ideas were tried out unsuccessfully to reduce the minimum towing speed. As battery-propelled U-boats had insufficient capacity to proceed submerged at 4 knots for any length of time, and it was already dangerous enough in 1944 to voyage at normal speeds without also towing three barges, the Type XXI Elektro-boot was elected for the operation which involved a 30-day tow across the Atlantic at 12 knots. The time required on the surface for the operation does not seem to have been disclosed.
When the campaign began in earenest, scientists at Peenemünde had found