Editing Nuclear weapon design (section)

===Levitated-pit implosion===
[[File:SandstoneYoke.gif|thumb|The ''Sandstone'' series of nuclear-weapons tests in 1948 proved the feasibility of increased yield efficiency via the levitated-pit design method.]]
The first improvement on the Fat Man design was to put an air space between the tamper and the pit to create a hammer-on-nail impact. The pit, supported on a hollow cone inside the tamper cavity, was said to be "levitated". The three tests of [[Operation Sandstone]], in 1948, used Fat Man designs with levitated pits. The largest yield was 49 kilotons, more than twice the yield of the unlevitated Fat Man.<ref>All information on nuclear weapon tests comes from Chuck Hansen, ''The Swords of Armageddon: U.S. Nuclear Weapons Development since 1945'', October 1995, Chucklea Productions, Volume VIII, p. 154, Table A-1, "U.S. Nuclear Detonations and Tests, 1945–1962".</ref>

It was immediately clear{{according to whom|date=October 2023}} that implosion was the best design for a fission weapon. Its only drawback seemed to be its diameter. Fat Man was {{convert|1.5|m|ft|0}} wide vs {{convert|61|cm|ft|0}} for Little Boy.

The Pu-239 pit of Fat Man was only {{convert|9.1|cm|in}} in diameter, the size of a softball. The bulk of Fat Man's girth was the implosion mechanism, namely concentric layers of U-238, aluminium, and high explosives. The key to reducing that girth was the two-point implosion design.{{Citation needed|date=June 2021|reason=Doubtful given Swan would be challenging to harden for laydown and ground penetration delivery.}}