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CHAPTER 1
The V Weapons
At about four o'clock in the morning of 13 June 1944, two elderly men sat in a sandbagged hole in the ground somewhere on the Kentish coast of England and listened. A week had gone by since the Allies had invaded France and there was always the chance that the Germans might try some sort of retaliation. And because these two men were members of the Observer Corps, and their task was to watch or listen for enemy aircraft, they were especially alert. Moreover they had just read a warning order which suggested that Hitler had something up his sleeve with which to bombard England, and the intelligence people had managed to put together enough information to suggest what form this retaliation might take.
Thus, when one of them heard what might have been a two-stroke motorcycle, but high in the sky, he alerted his companion. They looked up and there was a pulsing flame moving across the sky in the general direction of London, and this stuttering rattle of some peculiar engine. The observer took a quick sight through his plotting instrument, the teller reached for the telephone, and The Word was given 'Diver! 98 degrees, 4000 feet, 300 miles an hour, course towards London!' Diver was the code word to be used to warn of the new weapon. The Battle of the Buzz-Bombs was about to begin.
Vergeltungswaffe 1
The origin of the V-1 might be said to be the development of a suitable engine, because, if this had not been available, it is doubtful if the idea of a flying bomb would ever have occurred to anyone or, if it had, would have been taken seriously. It was the existence of a cheap and simple engine of sufficient power which clinched the argument. The engine development began in 1927–28 when an aerodynamicist called Paul Schmidt had the idea of a pulse-jet device. The theory was fairly simple once you had the inspiration: a tube was fitted with a screen of spring-loaded flaps at its front end, a petrol injection system and a spark plug. As it flew through the air, the air pressure forced open the flaps and air flowed into the tube. The flaps operated a valve and petrol was sprayed into the tube so as to make an explosive petrol/air mist. This mixture was then ignited by the spark plug. The explosion blew the flaps shut, and the blast then shot out of the rear end of the tube, driving it forwards. As the pressure inside died down so the air forced the flaps open and refilled the tube, more petrol was sprayed in and was ignited by either the hot interior of the tube or by residual hot gas from the previous blast, giving another pulse of power. And so it went on, several times a second.
There were one or two drawbacks to this device. In the first place it was incapable of sustaining itself at speeds under about 190mph, so that it was not possible to start the engine and take off in the normal way. It could not be throttled down or speeded up; it had its own natural speed and worked up to it from its initial 190+mph; once it achieved the optimum speed, it stuck closely to it. It was very inefficient above about 7,000 feet, where the density of the air began to fall off and the engine began to run out of breath. And after 30 to 45 minutes of operation the flap-valves were burned and damaged and the engine liable to fail. Therefore, although it was an ingenious method of propulsion, it had, it appeared, limited practical value in conventional aviation design. However, in 1934 Professor Schmidt suggested that it might be a useful method of driving an aerial torpedo, but nobody appears to have taken much notice of that idea.
In 1938 the Reichsluftministerium (Air Ministry, or RLM) had begun examining the jet engine concept, and in an endeavour to satisfy itself that all the likely avenues were being explored, it commissioned the Argus Motor Works to build a 'Schmidt engine'. Argus went ahead with this and produced an engine developing some 300kg of thrust, and delivered it to the RLM. They played around with it for some time, gave the matter some thought, then observed what the army was up to in Peenemünde and concluded that if the army was poking its boots into flying missiles, the air force ought to be doing the same, only more so. The RLM therefore called upon the Fieseler aircraft works for some ideas, and late in 1941 its chief engineer Lusser came up with some sketches. These were pondered, and finally, on 19 June 1942, development of the flying bomb was officially authorised. To conceal its purpose it was officially called the Flakzielgerät 76, a title which would suggest some sort of target for training AA gunners to anyone who heard it. The Fieseler company called it the Fi 103, in accordance with its usual system, but it is unlikely that anyone else ever called it that. To the people of southeast England and other places who suffered from it, it became 'the Doodlebug'. At the same time the Argus company was given a contract for the engine unit and the Walter company, specialists in rockets and fuels, was handed the problem of getting the device into the air at something over the critical 190mph speed so that it would sustain flight.
Work moved ahead quite rapidly; the first successful launch of the FZG 76 was made on 24 December 1942 at Peenemünde. It was, though, followed by numbers of unsuccessful launches as various problems were encountered and solved.
The FZG 76, as it was eventually perfected, was a mid-wing monoplane with the Schmidt engine mounted above the rear of the fuselage and tail fin. Inside the body, from front to rear, were an air log (a propeller-driven counter which measured the distance flown); the warhead containing 1,870lb of high explosive and three different types of fuze; a fuel tank containing 150 gallons of low-grade 75-octane petrol; two compressed air tanks pressurising the fuel system and supplying air to various servos controlling the rudder and tail elevators; a 42-cell 30-volt battery; a master gyroscope; and the various servos and other controls.
The weapon was prepared by firstly filling the fuel tank, fitting a fully-charged battery and charging up the compressed air tanks. It was then taken to a non-magnetic area where the magnetic master compass was checked for deviation and set at the correct bearing from the launch site to the target, after which it was trollied to the launching ramp.
The launching ramp was essentially a slotted tube about 150 feet long, in eight sections which could be bolted together, supported on concrete and steel at a suitable launching angle. Both ends of the tube were open, and the rear had a form of bayonet joint. A large dumb-bell shaped piston, with a fin on one side, was loaded into the rear of the tube like an artillery shell, the fin protruding through the slot, and a flexible sealing tube was inserted into the firing tube and held with wires close to the slot. On top of the firing tube was the launching trolley, a simple framework on to which the actual missile was placed, and behind which the fin on top of the firing piston bore.
The 'combustion chamber trolley' was now wheeled up behind the rear end of the firing tube and locked to it by means of the bayonet joint. This trolley carried containers of potassium permanganate (known to the Germans as Z-Stoff) and hydrogen peroxide (T-Stoff), three bottles of compressed air, and the combustion chamber itself, a heavy steel forging.
Just off to the left side of the ramp was the 'distributor unit', mounted on a steel platform. This carried more compressed air tanks, pressure gauges and distribution valves supplying compressed air to the missile, firstly to blow air into the front of the duct and simulate flight, and secondly to switch on the fuel valve (and switch it off again should there be any malfunction). There was also a transformer and trembler coil which supplied power to the engine spark plug by a flexible lead.
With the missile placed on the trolley and the trolley hard back against the fin on the firing piston, the various operators took cover in a specially prepared pillbox some distance from the ramp and the launch procedure was started. Air was blown in to the engine and the spark plug fired so that the engine started and ran at full power. After about 7 seconds of this warm-up, the valves on the combustion chamber trolley were opened by remote control; this injected T-Stoff and Z-Stoff into the combustion chamber under pressure, where their reaction produced a massive volume of super-heated steam. The firing piston was restrained by a shearable bolt, and as soon as the pressure was high enough to shear this the piston began moving up the firing tube, pushing the firing trolley and the missile ahead of it. The gas pressure behind the piston forced the sealing tube into the slot, forming a crude and not very effective gas seal.
The volume of steam and its pressure was enough to ensure that the missile was flying at about 250mph when it left the end of the launching tube. At the end of the tube the huge piston simply shot out of the tube, and as it fell away from the trolley, so the trolley fell from the missile, leaving it climbing at the same angle as the launching ramp and gradually accelerating.
Each site was equipped with several pistons and two combustion chamber trolleys. While one trolley was in use the other was being recharged with compressed air and fuel. After launching, the base of the ramp, which was stained by permanganate, had to be washed down by personnel in rubber boots and protective clothing.
The missile was now climbing steadily at about 500 feet per minute, and the various control systems began to function. The master magnetic compass compared the missile's heading with the azimuth set into the compass. If it discovered a deviation it would send a blast of compressed air down a duct to the master gyroscope, nudging it in the required direction. Movement of the gyro was then converted into another movement of compressed air to the relevant servo motor controlling the tail fin, steering the machine into the correct track. A similar barometric sensor sampled the air pressure and once it decided that the operation altitude of 3,000 feet had been reached, the elevator controls were operated to bring the machine into level flight. It generally took about six minutes for the FZG 76 to reach this altitude, after which it settled down at its optimum speed. This could be anything between 300mph and 420mph, depending upon the natural frequency of the engine and various other factors. An unusual point was that once the machine had reached its optimum speed it tended to stay at it because, although it was using up fuel and therefore getting lighter, any advantage this might have given was offset by the mechanical deterioration of the engine as the fuel flaps burned away.
Before firing the air-log had been set at the range to the target. As the missile flew so the air-log propeller turned and, through a gearing system, gradually counted up the air miles flown. When the set distance had been covered, two detonators were fired which locked the rudder and elevators and drove two sets of spoilers down from the tail, so forcing the machine into a steep dive. This usually caused the fuel supply, which by this time would be low, to fail and the engine thus stopped; though on some occasions the machine went into a fully powered dive, the engine cutting out just before impact. A fairly high percentage of machines failed to go into a steep dive immediately and instead made a long glide before turning into a final dive. It appears that the nature of the final dive was largely governed by the amount of fuel left in the tank and its effect upon the machine's balance; the more fuel, the steeper the dive.
As soon as the missile struck the ground, or any other solid object, the warhead detonated. And the fuzing system of the warhead was so efficient that of the first 2,700 incidents monitored in Britain, only four missiles failed to detonate. The system consisted of one electrical impact fuze (ElAZ 106), one mechanical all-ways fuze (AZ 80A) and one mechanical clockwork delay fuze (ZZ 17B). The impact fuze, which was powered from the 30-volt battery and armed by the air log about 40 miles after launch, had three switches; a pressure plate in the missile nose for cases of direct impact; a pressure switch on the underside of the fuselage for a belly landing; and an inertia switch inside the fuze itself which would operate on rapid deceleration if the other two should fail to function. There was even a resistor-condenser circuit, charged up by the battery, which contained enough electricity to fire the detonators of the fuze should the battery connection be damaged on impact.
The AZ 80A fuze was a fairly simple trembler switch type of fuze which would make an electrical contact and detonate the warhead no matter what angle the missile hit the ground. It was armed by a clockwork device which was set off by a wire being pulled out during the launch and which armed the fuse some 10 minutes after leaving the ramp. The fuze was there simply as an insurance if the ElAZ 106 failed to work.
And finally the ZZ 17B delay fuze was a clockwork delay adjustable up to two hours. This, too, was started at launch, and should the other fuzes fail and the missile land in one piece then, after the delay had run its time, the warhead would be detonated.
Once all this technology had been mastered and proved to work, the FZG 76 went into production. It was designed with simple mass-production in mind from the very start of the project, a distinctly different approach to that taken by the designers of the V-2 rocket. It was constructed almost entirely of mild steel plate (later versions used wooden wings) and each of the component parts was of the simplest form, even if it meant additional weight.
Manufacture of the components was dispersed widely through Germany, and assembly of the components into complete missiles was also dispersed in various places. The largest assembly plants were in Nordhausen, in the Harz Mountains about 50 miles west of Halle; Dannenberg, some 50 miles southeast of Hamburg; Fallersleben, a few miles north of Brunswick, where the Volkswagenwerke at KDF-Stadt was taken over; and Stettin (now Szczecin in Poland), the Baltic port close to Peenemünde. The early missiles, used for tests and training, were, of course, built entirely within the Peenemünde complex, and it was here that a newlyformed anti-aircraft regiment, Flakregiment 155(W), was mustered and set to training on the FZG 76 in 1943.
The Nordhausen Mittelwerke was a massive subterranean factory run almost entirely on slave labour; political and other prisoners who were, quite literally, worked to death. It was also charged with the assembly of the V-2 missiles and of aero-engines and all manner of munitions. Less is known of the other assembly plants, since they were not such a remarkable construction as the Mittelwerke but were fairly conventional factories dispersed into areas of little apparent importance so as to minimise their chance of being attacked from the air.
The operational use of the FZG 76 was originally planned to begin in December 1943, but two main schools of thought emerged on the actual method of use. The first, championed by Field Marshal Milch of the Luftwaffe was to construct a limited number of immense underground bunkers which would combine the functions of storage, preparation and launching. By amply stocking these well before the operational date, and keeping them well-supplied with missiles, it would thus be possible to bring a continuous stream of missiles to bear against England, saturating the defences and causing enormous damage.
The other view, held by General von Axthelm and others, was that such enormous constructions would undoubtedly come to the notice of aerial reconnaissance and would thereafter be bombed unremittingly, preventing them from functioning at all. He preferred a large number of simple sites which could be quickly constructed and as quickly abandoned if they were bombed. With a large number of sites it would be probable that half of them would never be discovered and thus the offensive would be able to continue; not, perhaps at such an intensity, but at least at a sufficient rate to cause the same amount of damage, though over a longer time.
A third alternative was also suggested; carry the bombs into the air beneath larger aircraft, fly them close to the English coast, and then release them. This would allow a much deeper penetration into Britain within the limited flight time of the missile. Experiments with this idea duly began, using the Heinkel 111 as the parent machine.
(Continues…)
Excerpted from "German Secret Weapons of World War II"
by .
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