Authors: Brian Ford
Tags: #Secret Weapons: Death Rays, #Doodlebugs and Churchill’s Golden Goose
In the early tests of the Fritz-X the carrier was a Heinkel He-111 and some of the He-177 aircraft were adapted to carry the weapon, though they never became operational. When the Fritz-X entered operational service it was aboard the Dornier Do-217 bomber. In July 1943 the first Fritz-X was launched in a raid against Augusta in Sicily. The following month, six of the bombers attacked the Italian fleet, which was sailing across the Mediterranean towards Malta as the Italians had signed their armistice with the Allies. This infamous Armistizio di Cassibile had been signed after the Allied successes in North Africa in 1943, after which the Allies landed in Italy, occupied Sicily and even bombed Rome. It was agreed that the Italian naval ships would transfer to Malta and the Germans became determined that they should not become available for use by the Allies. And so, on 9 September 1943, the battleship
Roma
was attacked by Fritz-X guided bombs dropped by the Dornier bombers. Her magazines exploded in a catastrophic blast with the death of 1,255 crew. Among them was Admiral Carlo Bergamini. Although
Roma’
s sister ship
Italia
was hit she managed to limp into port in Valetta, Malta.
Two days later a German Fritz-X attack was directed against a convoy of United States Navy vessels including the USS
Savannah
, one of America’s top light cruisers. Observers spotted a Dornier bomber flying towards the USS
Philadelphia
. A bomb aimed at the ship narrowly missed, and exploded about 50ft (15m) away. The
Savannah
immediately increased her speed to 20 knots (37km/h) and then saw a second Do-217 K-2 attacking out of the sun from an altitude of 18,700ft (5,700m). The gunners opened fire, but the plane was not hit and the Fritz-X could be seen flying towards the American ship, leaving a trail of smoke from its flares as it flew. Its steel-piercing design ensured the bomb struck the ship and passed straight through three decks before exploding deep inside the vessel. The blast tore a hole in the keel and ripped along the port side of the ship. Fires started in the magazines and for half an hour a continuous series of explosions prevented fire-fighters from tackling the blaze. Nearly 200 sailors were killed in the attack. The crew responded brilliantly, sealing off flooded compartments and correcting the ship’s list to port. After 8 hours of frantic activity, her boilers were relit and the ship set off to steam to Malta for emergency repairs. Four days later, four sailors were found to have survived trapped behind water-tight doors and sealed inside. After returning to the United States, it took eight months to repair the damage caused by this single guided bomb.
Next to be attacked was the British cruiser HMS
Uganda
which was struck by a Fritz-X near Salerno on 13 September 1943. The guided bomb hit at full speed and penetrated through seven decks before exploding, blowing out a section of keel. Later the battleship HMS
Warspite
was hit, the Fritz-X penetrating six decks and detonating in a boiler room.
At first, the attacks were thought to be administered by conventional weapons but the angular trajectory revealed by the trailing smoke soon revealed the fact that the bombs were radio-controlled. The German system involved a Kehl transmitter, operated by the attacking pilot, and a receiver aboard the bomb. This system had been designed for use on the Hs-293 (addressed below) and there was a choice of 18 Kehl/Strassburg frequencies from which to choose the command connection. As soon as the radio control had been recognized by the Allies, radio-frequency jamming began. It was not a success. The frequency was rarely selected correctly; also other simultaneously attacking aircraft would chose disparate frequencies and the defences could use only one at a time. They were quickly overwhelmed.
In time, examples of unexploded Fritz-X missiles were obtained by the Allied scientists and the control mechanism was examined closely and became better understood. After several months, the British designed and constructed their Type 650 transmitter, which worked on the common frequency of 3MHz which was subsequently used as the basic communications frequency for all transmissions to the bombs. This worked for all attacks, and did not rely on finding the command frequency for each individual weapon. Due to the Allies’ increasingly efficient counter-measures, the Fritz-X missile was no longer of use to the Germans by the time of the Normandy landings – though its career earlier in World War II was highly successful.
The Fritz-X needed adequate height to function as a weapon capable of piercing a ship’s steel decks. Its minimum release altitude was 13,000ft (4,000m) and the minimum flight distance was about 3 miles (5km) from the target. In practice, the chosen altitude was 18,000ft (5,500m). This posed a problem for the pilot of the bomber that delivered it: the plane could easily fly beyond the flight-path of the missile, losing visual contact. Pilots tended to go into a slow climb, thus reducing speed over the ground, so that they remained within sight of the missile and could steer it on its way. The Allies discovered this, of course; it meant that the bomber was now a sitting target for the anti-aircraft gunners. When this ruse worked, it worked well; pilots had a very high rate of success and the attacks on bombers that had launched a Fritz-X bomb became easier with time.
In order to provide the launching bomber with a safe distance at which to operate, German secret weapon scientists pioneered the deployment of extremely narrow wings, which offered an extended glide path. This was the Blohm & Voss
Hagelkorn
(Hailstone) glide bomb. It was designed by Dr Richard Vogt and the prototypes were designated the BV-226. In December 1943 the weapon went into series production as the BV-246.
Vogt’s idea was that this secret weapon could glide for extended distances, directed by radio control, thus allowing the mother ship which delivered the weapon to remain safely out of range. In the event, the control system was abandoned. The final design was for a conventionally tapered body fitted with a twin fin and rudder. The shoulder-mounted wings were revolutionary – they were extremely long and thin. To obtain strength, the main rib was constructed from steel and the profile was then laid on to produce the desired aerodynamic shape. In an era when plastics were not yet readily available, the moulded wing was made … from concrete. The Hagelkorn missile was 11ft 6in (3.53m) long with a wingspan of 21ft (6.4m). Its top speed would have been 560mph (900km/h) and it carried a warhead weighing just under 1,000lb (435kg).
The glide ratio was 1:25. It was intended that the glider would be launched from a Heinkel He-111 or Ju-88 at a cruising height of about 23,000ft (7,000m). From that altitude the glide-bomb could travel for over 100 miles (175km). Anti-aircraft fire could not touch the bomber at that distance.
In 1945 there was an urgent redesign to include an ultra short wave radio-detection device known as
Radieschen
(Radish). This was intended to detect enemy radar transmissions, so the weapon could home use Allied radar stations as a target. Prototypes of these homing glide bombs were constructed with a gyroscope to stabilise the flight path and with the detector built into a re-configured nose assembly. Ten were flown on a test range, eight of which failed. The two that succeeded had impacted within 6ft (2m) of the target.
About 1,000 were produced, though none were used operationally. The success of the V-1 meant that the BV-246 was superseded – though the design concept went on to find a home in high-altitude reconnaissance aircraft. The American U-2 spy plane was built to a similar design, and the novel construction of the Hagelkorn bequeathed a legacy to post-war engineers.
Hs-293
Since the vulnerability of the pilot had been recognized early in the war, the German engineers had set out to find an answer. And, as the Fritz-X was being developed as a controlled missile, research was directed to a flying weapon that could regulate itself rather than being steered by a pilot. In 1939 the Gustav Schwartz Propellerwerke produced designs for a glide bomb. It did not have real-time radio control, so the bomber that delivered it did not have to stay on location. Instead, it had its own onboard autopilot that flew it straight and level towards the target. This was the brainchild of Professor Herbert Wagner, chief designer at the Henschel Company, who immediately took up the project. Wagner was an Austrian aeronautical designer who was awarded his doctorate by the University of Berlin when aged 23. He decided to fit the production version with a HWK-109 rocket that could provide 1,320lb (600kg) of thrust for 10 seconds. Unpowered glider versions were first dropped from He-111 aircraft, and powered test runs had been successfully completed before the end of 1940. The finished version was the Hs-293, designed to carry a 1,100lb (500kg) bomb.
A course set by a fixed autopilot proved to be a limitation, and so a radio-controlled system was also tried. This was the highly successful 18-channel Kehl/Strassburg that had also been fitted to the Fritz-X bomb discussed earlier. Unlike the Fritz-X, the shell was contained in a conventional steel housing – this was not a steel-piercing missile. But the Hs-293 was susceptible to the increasingly sophisticated jamming techniques of the Allies, conducted not only by the British but by the Americans and Canadians as well. A particularly successful example was the MAS jammer which could intercept the signals and take over control of the Hs-293 and send it crashing into the sea. Even so, from 1942 to the end of the war, more than 1,000 Hs-293s missiles were manufactured and these glide bombs were a remarkably successful weapon of war.
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.