The first U.S. nuclear weapons in 1945 were the implosion “Fat Man” (FM) bomb, which used two plutonium-239 hemispheres placed in a central cavity of a 5,000-pound high- explosive lens system, and the gun-type “Little Boy,” using a solid uranium-235 projectile fired into U-235 target rings. 3 While crude laboratory devices, these weapons became the basis for future weapons development – leading to levitated-pit bombs with insertable nuclear components by 1947, early thermonuclear warheads in 1954, and by 1956, sealed-pit, one-point safe, fission, and boosted thermonuclear weapons. 4 It wasn’t until 1962 that the final FM-type implosion bomb, the Mark 6 Mod 6, was retired from the U.S. stockpile. The last gun-type weapon, the W33 artillery-fired atomic projectile, was being removed from the stockpile when I arrived in Germany.
basis, a medium-sized implosion system with detachable components to include an electronic cartridge and firing set/X- unit. There are some deficiencies which I won’t address, but other features of the warhead show a sophisticated level of design engineering. Such a small-diameter system, similar to the long-retired U.S. Mark 7 warhead and the Soviet RDS-4 bomb, can readily be adapted to a number of systems – from air-dropped bombs, short-range rockets, medium- range ballistic missiles, and long-range missile warheads. The Mark 7 warhead was approximately 30 inches in diameter, and used 92 detonators. 5
More than adequate to place Pacific Rim population centers and U.S. and allied military bases under the threat of nuclear annihilation.
Looking at the photos of the nation’s mockup warhead, it’s apparent from various angles that the DPRK has designed and produced, on a limited
North Korea’s nuclear warheads are likely similar to the ‘50s-technology Mark 7 fission bomb.Inset – a specialist tests detonator contacts on the warhead (photo of Mark 7 bomb: Wikipedia. Mark 7 warhead: Department of Energy Historical Films).
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