The single advantage of the design was that stages could be removed, if the distance to be covered was reduced. Rheinbote looked spectacular, and over 200 were used against the strategically important Belgian port of Antwerp. They caused limited pockets of damage in unpredictable areas of the city, but this missile was of little use to anyone — and existed only because of the Führer’s capricious decision.
We are all familiar with glide missiles. Although the term has the ring of modernity about it, and sounds like a state-of-the-art weapon of the twenty-first century, it is a concept that was in fact born back in World War I. It was in October 1914 that Wilhelm von Siemens proposed a revolutionary new concept that was to become the torpedo glider. In principle, it was a conventional torpedo with a primitive unmanned glider fixed above. The glider was fitted with flares to enable its course to be tracked by the attacker, and was controlled by fine wires spooled out by the controller. Siemens-Schuckertwerke had already experimented with radio-controlled attack boats, the Fernlenkboote (FL-boats) and flight testing of the proposed guided aerial torpedo began in 1915. It was intended to glide the device on course towards the target, where the glider would become detached on a signal from the operator, and the torpedo would be dropped into the sea to home in on its target. The device was just ready for production at the very end of World War I, but was not used in warfare.
With the re-emergence of pilotless planes in World War II, a reliable guidance system was now urgently needed. Infrared, the heat radiation given off by an engine, could be detected and this offered the best way for a missile to home in on an enemy aircraft. Like light, infrared travels for immense distances and in straight lines. The Germans soon realized that a steering system that homed in on the infrared given off by an engine could follow an enemy aircarft for miles.
The first in the world to use infrared tracking equipment was a missile named the Enzian (named after Gentiana clusii, the gentian flower). As we have discovered the first rocket fighter, the Messerschmitt Me-163 Komet, posed practical problems for the pilot. It had a short flight time and high speed up to 596mph (959km/h) at 39,000ft (12,000m) which made it difficult for the crew to find and attack their target in time. Designers at Messerschmitt decided to build a similar aircraft that could carry a huge payload to its target, and would dispense with the need for a pilot aboard. The Enzian would be launched from a sloping ramp with the aid of four booster rockets to attain a maximum speed of 600mph (almost 1,000km/h). It would be 12ft (4m) long and weigh 4,350lb (about 2,000kg) with a range of some 18 miles (30km).
Rather than risk losing a pilot, it was proposed to control the flight of Enzian from the ground. The operator would fly the Enzian in front of an enemy bomber and it would then detonate with great destructive force. The plan was for a bomb with a lethal radius of about 150ft (45m) which could be detonated by means of a proximity fuse. Work began in September 1943 and by May 1944 some 60 airframes had been manufactured. The remaining problem was the lack of a suitable rocket motor. Since work on the Rheintochter missile was proceeding smoothly, this engine was selected for the Enzian and modification began to produce a series of the motors for test flights. These trials proceeded well, though the proximity fuse proved problematic. At this point a remarkably simple new device, code named Madrid, was developed. It featured a light-sensitive photoelectric cell fixed in front of a steerable mirror; a series of vanes masked the cell and the signal from the target — a shadow — was always kept in the middle. The steering system in the Enzian followed the shadow in the mirror and made corresponding adjustments to the trajectory, so the target was bound to be followed. As the tide of war turned increasingly against the Germans, it was realized that there was no time to perfect the system, and for this reason the device never came into use. After the war, with the developers transported to the United States under Operation Paperclip, the work proceeded and the design was eventually perfected. It was put in use by the United States Navy as the guidance system for their AIM-9 Sidewinder missile. This is the most widely used air-to-air missile in the West, and it is said that it will remain in use for many decades to come — yet it arose from German technology in World War II.
During the Spanish Civil War of 1936–39, bombs were designed to penetrate steel which proved effective against shipping, but the Luftwaffe soon discovered how difficult it was to hit a moving vessel squarely. The idea began to form of a radio-controlled bomb that could be steered on course during its free fall, and the first experiments began as early as 1938. In 1939 the first experimental bombs were designed with tail-fins and guided with radio-controlled spoilers. These could allow the bomb aimer to control the trajectory and maximize the chances of hitting the target. The Ruhrstahl Company, already expert at design and production of bombs, was brought in to move development towards the production stage. The result was the successful Fritz-X bomb, which was controlled by spoilers fitted to the four tail fins. It was tested in various configurations, and the cruciform tail unit proved to be most adaptable, and was eventually used for other controllable weapons of war.
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.