T-12 Cloudmaker

The T-12 (also known as Cloudmaker) demolition bomb was developed by the United States from 1944 to 1948. It was one of a small class of bombs designed to attack targets invulnerable to conventional "soft" bombs, such as bunkers and viaducts. It achieved this by having an extremely thick hardened nose section, which was designed to penetrate deeply into hardened concrete structures and then detonate inside the target after a short time delay. This generated an "earthquake effect".

The T-12 was a further development of the concept initiated with the United Kingdom's Tallboy and Grand Slam weapons developed by the British aeronautical engineer Barnes Wallis during the Second World War: a hardened, highly aerodynamic bomb of the greatest possible weight designed to be dropped from the highest possible altitude. Penetrating deeply in the earth before exploding, the resulting shock wave was transmitted through the earth into structures. The resulting could also undermine structures. The bomb could also be used against hardened targets. These types of bombs can reach supersonic speeds and have tail fins designed to spin the bomb for greater accuracy.

Originally designed to meet a 42,000 lb (19,000 kg) target weight (the maximum payload for the Convair B-36 "Peacemaker" bomber), the original design with its hardened case was slightly less than 43,000 pounds. The final T-12 weighed 43,600 lb (nearly 20 metric tons). This was twice the size of the United States' previous largest bomb, the 22,000 lb M110 (T-14), the American-built version of the British Grand Slam. The T-12 was not a simple scale up of the M110, but incorporated modifications based on testing and calculations. The B-36 was redesigned so it could carry the T12, although a converted B-29 Superfortress was used for testing.

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