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HISTORY The size of aerial bombs available up to this time, and the difficulties in accurate bombing of targets meant that bombing any massive or protected structures had been a pointless task. The British engineer Barnes Wallis had earlier considered the strategic use of bombs as a means to destroy the enemy's capacity to wage war by hitting its infrastructure and manufacturing bases and to this end developed improved bomb designs based on large single bombs early in the war. He had presented his ideas for a 10 ton bomb working on the earthquake principle in his famous paper ''A Note on a Method of Attacking the Axis Powers''. His calculations showed that a very large bomb exploded deep underground beside a target would form a Camouflet (cavern) rather than a crater. All the explosive energy would be contained within the ground and the shock transmitted into the foundations of the target, which would then collapse into the camouflet. More importantly, the shockwaves transmitted though a non-compressible medium are less attenuated by distance than a compressible medium such as air. The bouncing bombs that destroyed dams used this principle by using water as the non-compressible medium. If such a large bomb were exploded closer to the surface a huge single crater would be created, which would tax the capability of earthmoving equipment to fill in, and could effectively disrupt targets such as railway marshalling yards for long periods. However the carrying capacity of British bombers was limited and the capability to carry such a huge weapon to the height required was beyond consideration at that time - leading Barnes Wallis to draw up a bomber sufficient to the job, an idea which was not eventually pursued. The Ruhr dams, though, were one of the strategic targets he had considered and Barnes Wallis was commissioned to develop a means of destroying them. He had to make do with a maximum bomb size of 6 tons, and overcoming the problems of delivering the weapon to the target accurately led to the revolutionary " Bouncing Bomb ", which utilised his massive contained blast idea but with water replacing the earth. The project distracted Wallis from his designs for a very large earth penetrating bomb until the successful use of the bouncing bombs by the Dam Busters in Operation Chastise which validated his ideas. The RAF still needed a bomb that delivered a single large blast and which could penetrate hardened targets like battle ships, bunkers and railway tunnels (a Bunker Buster ), or to create a camouflet which would undermine foundations of structures like bridges causing them to collapse, and as the ability to lift 10 tons was still distant, Wallis was asked to consider what could be done with a smaller bomb and he worked on scaled down designs - one of which would become the 5 ton Tallboy. The actual design and production of Tallboy was done without a contract on the initiative of a single official within the Ministry. As such the RAF were using bombs they had not bought and which were actually still the property of the manufacturers; Vickers . This situation was regularised once their capabilities were recognised. Tallboys were used with great success against massive targets during the end phases of the war; targets which had been thought to be invulnerable to attack using conventional bombing techniques. Amongst many spectacular accomplishments, the attack on the V2 facility at Wizernes , France stands out. Here, a cupola roof designed to be absolutely bomb-proof was disrupted by Tallboy and Grand Slam hits undermining the foundations - a perfect vindication of Barnes Wallis' theories. In another attack on the Saumur Tunnel , one Tallboy passed straight through the hill and exploded right inside the tunnel 60 feet below the surface. Inexplicably, the development of heavyweight, precision-delivered, ground-penetrating bombs seems to have ceased after 1945, with the assumption that nuclear weapons would be used on major targets in the future. This has left the UK and US with few options when attacking hardened targets in the non-nuclear 'police action' small wars of the late 20th century. After the Iraq War the US announced that they were to commence research into heavy ground penetrating weapons. DESIGN Most large Allied World War II aircraft bombs had very thin skins to maximise the weight of explosive which a bomber could carry — this was an improvement on the early part of the war when the actual HE content of British bomb designs was low. To be able to penetrate the earth (or hardened targets) without breaking apart the casing of the Tallboy had to be strong. Each was cast in one piece of high tensile steel that would enable it to survive the impact before detonation. At the same time to achieve the penetration required, Wallis designed the Tallboy to be very Aerodynamic so that when dropped from a great height it would reach a velocity higher than traditional bomb designs. In the final design the tail of the bomb was about half the overall length of the finished weapon — the bomb casing was some 10 feet (3.05 m) of the overall 21 foot (6.35 m) length. Initially the bomb had a tendency to tumble, so the tail was modified — the fins were given a slight twist so that the bomb spun as it fell. The gyroscopic effect thus generated stopped the pitching and yawing, improved the aerodynamics and improved accuracy. The improved design worked so well that it was found in development that it passed through the Sound Barrier as it fell. When dropped from 20,000 ft (6,100 m) it made an 80 ft (24 m) deep crater 100 ft (30 m) across and could go through 16 ft (4.88 m) of concrete. . W. J. Lawrence wrote about the Tallboy bomb in his book, No 5 Bomber Group (1951)
The weight of the Tallboy and the high altitude required of the bombing aircraft meant that the Lancaster Bombers used had to be specially adapted. Armour plating and even defensive armament were removed to reduce weight and the bomb-bay doors had to be adapted. Even then the Lancaster was not capable of reaching the bomb's intended dropping height of 40,000 ft (12,200 m) but only around 25,000 (7,700 m). At the same time No. 617 "Dambusters" Squadron trained in the use of a special bombsight the Stabilizing Automatic Bomb Sight (SABS). For accuracy multiple corrections had to be made for temperature, windspeed etc. However it was only effective if the target could be identified and several missions were cancelled or unsuccessful because of difficulty in accurately identifying and marking the targets. Each bomb was a precision-built instrument of war made from expensive materials and carefully finished. They were not considered expendable and if not used on a raid were to be brought back to base rather than safely dropped in the sea. The value of the weapon offset the additional risk to the aircrew. The Tallboy was used to attack strategic targets that could not be destroyed by other means. When it was found that the Lancaster could be modified to carry a bomb larger than the Tallboy, Wallis produced the even larger Grand Slam Bomb . TALLBOY OPERATIONS
VITAL STATISTICS REFERENCES
NOTES SEE ALSO |
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