Secret Weapons (10 page)

Meanwhile, Guy Gibson’s 617 Squadron remained together and they were subsequently given the opportunity to deliver Barnes Wallis’s later weapons. The Cookie 5-ton bomb was carried by Lancaster bombers and used with great effect to attack submarine pens in France and German warship bases in the fjords of Norway. Although it proved a success, it was no more than a vast, conventional blast bomb. Barnes Wallis had in mind a very different secret weapon which would penetrate the ground and deliver such powerful shockwaves that it would bring down buildings and bunkers for a considerable distance around. Whereas a conventional bomb (no matter how large) did its damage through air-blast, Barnes Wallis’s revolutionary new bomb would generate a miniature earthquake, by setting up huge ground waves of energy. These could demolish a building from below.

Other solutions were sought to increase the penetrating power of high-explosive bombs. Towards the end of the war, a rocket-assisted high-impact bomb was conceived by the Royal Navy’s Captain Edward Terrell as an alternative answer. The rocket could give a smaller bomb the velocity needed to penetrate thick concrete. The weapon weighed only 4,500lb (2,000kg) and could be dropped from a safe altitude of 20,000ft (about 6,000m). When it had descended to 5,000ft (1,500m) a barometric fuse would fire a rocket motor in the tail. This accelerated the bomb to give it a final speed of 2,400ft/s (730m/s). This secret weapon was first carried under the wings of B-17 Flying Fortress bombers used by the 92nd Bomb Group on 10 February 1945 against the S-boat pens at IJmuiden, Netherlands. Altogether, 158 of these so-called Disney bombs were used operationally by the end of the war in Europe.

Barnes Wallis scaled down his proposals for his gravity-assisted penetrating bomb, and in 1944 designed instead the 12,000lb (5,400kg) Tallboy bomb, which could be carried by the current bombers. Later in the war, the Avro Lancaster improved to such an extent that it could just support a 10-ton payload and so, as we shall see, the 22,000lb (10,000kg) Grand Slam bomb was finally put into production. It was a secret weapon of unprecedented power. As in the case of the Tallboy bomb, the Grand Slam was spin-stabilized by its fins and was built with a thick, heavy steel case to allow it to penetrate deep layers of the ground unscathed. Dropped from high altitude, it would impact at nearly the speed of sound. During manufacture, hot liquid Torpex explosive was poured in to fill the casing and this took a month to cool down and solidify. Torpex (named because it had been developed as a TORpedo EXplosive) had more than 150 per cent the force of TNT. The finished bomb was so valuable that aircraft that could not drop their weapon in an abortive mission were ordered to return to base and land with the bomb intact, instead of jettisoning it over the open sea. Barnes Wallis had planned to create a 10-ton weapon in 1941, but it was not until June 1944 that the bomb was ready for use. It was first dropped on the Saumur rail tunnel from Lancaster bombers of 617 Squadron. No aircraft were lost on the raid, and one of the bombs bored 60ft (18m) through the rock into the tunnel, blocking it completely. These massive ‘earthquake’ bombs were also used on the great concrete stuctures that the Germans were building to protect their rocket storage bunkers and submarine pens, and caused considerable damage. The Valentin submarine pens at Bremen, Germany, were made with reinforced concrete roofs some 23ft (7m) thick yet they were penetrated by two Grand Slam bombs in March 1945.

These ground-penetrating bombs are among the secret weapons that have gone on to give rise to present-day developments. Remote guidance was added to the Tallboy bomb by the United States during the Korean War. The resulting weapon was the 12,000lb (5,400kg) Tarzon bomb, used with devastating effect against a deep underground control room near Kanggye. Bunker buster bombs were also dropped at the Ali Al Salem Air Base, Kuwait, in 1991 as part of Operation
Desert Storm
. At the outbreak of the First Gulf War none of the NATO forces possessed such a weapon, so some of the original Barnes Wallis bombs were brought out of museums and used as templates for the construction of 2-ton bombs. They were laser guided by the United States forces and proved highly effective.

During the late 1990s a nuclear bomb was being designed by the United States for use in tactical warfare. Known as the Robust Nuclear Earth Penetrator it underwent extensive design and development even though the use of nuclear weapons was prohibited by international agreement. Work on the project continued until it was finally cancelled by the Senate in 2005. Meanwhile, in 2007 the Boeing Company announced that they had carried out successful tests of their Massive Ordnance Penetrator (MOP) weapon at the White Sands Missile Range, New Mexico. This bomb, also known as the Big Blu and Direct Hard Target Strike Weapon, is a 30,000lb (14,000kg) penetration bomb designed to be delivered by a B-52 Stratofortress or a B-2 stealth bomber against heavily protected subterranean targets. This is a project for the United States Threat Reduction Agency, and is designed to hit the ground at supersonic speeds so that it can penetrate deeply prior to detonation. Most of the mass is in the casing, not the explosive component. All of his stems from the work of Barnes Wallis during World War II, so once again the legacy of these secret weapons remains with us to this day.

Carrying artillery and ammunition to the war front is a time-consuming and tedious business. Far better, the Germans realized, for the weapons to take themselves to the front. From the start of the war – and indeed in the Spanish Civil War, which was a prelude to World War II – the Germans began to look at ways of carrying explosives by plane, and dive-bombing soon became an early strategy in planning an attack. But the bombers were vulnerable, and losses were soon rising fast. So the Germans turned to designs for planes without pilots. These ideas could be far-reaching, because – since there was no crew whose lives could be put at risk – the planes themselves would be expendable. Nothing need be omitted in the search for an answer.

By 1942, Rheinmetall-Borsig AG had risen to the challenge, and announced the design for their
Rheintochter
(Rhine Maiden) surface-to-air missile. It was a remarkable device, a two-stage surface-to-air vehicle which was named from Wagner’s famed
Ring
cycle. The Rheintochter was designed with a cylindrical fuselage bearing four rounded steering fins operated by servo-mechanisms. Four large swept-back fins on the first stage kept the flight of this solid-fuel rocket-powered device stable in flight. A later modification substituted a liquid fuel engine, but even this did not provide the desired performance and – although many were launched – the project was never fully operational, and it was finally cancelled in December 1944.

In 1943 development was announced of the successor to the Rheintochter – it was the
Rheinbote
(Rhine Messenger) and was designed by the Rheinmetall-Borsig Company. This was a design for a slender 37ft (11.4m) rocket that could deliver a modest payload over distances up to 125 miles (200km). The solid propellant was to be diglycol dinitrate and the missile would be a four-stage rocket: the first stage would launch the main rocket from the ground before being discarded; the second and third stages would fire in succession, carrying the payload aloft, and the final fourth stage would fire it into its maximum altitude where it was set on its course to the target.

However, there was a major problem with accuracy. Each of the four stages was stabilized by four fins at the aft end of the rocket, and the stages were ignited in turn as the fuel charge from the previous stage reached the end of its burn. This was clearly a rocket of limited appeal, for it consumed 2 tons of steel in manufacture, with all the concomitant requirement for energy, it demanded more than half a ton of fuel propellant, yet it could deliver no more than a 44lb (20kg) explosive to its target. It produced no fragment damage and could make a crater no more than 5ft (1.5m) across. Other projects – like Herbert Alois Wagner’s design for the
Schmetterling
(Butterfly) – seemed to offer far more promise and informed opinion was that the rocket was militarily valueless. This cut no ice with the High Command; the weapon could be simply understood and a four-stage device was simply too good to miss. Hitler and General Hans Kammler (who reported to Reichsführer Heinrich Himmler directly) immediately ordered production of this worthless missile. Tests were carried out, but it proved impossible to calculate the accuracy because the impact craters were so small that they could not be found.

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.

Flying Fritz

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.